— Simple lexical analysis

shlex
— Simple lexical analysis¶
Source code: Lib/shlex.py
The shlex
class makes it easy to write lexical analyzers for
simple syntaxes resembling that of the Unix shell. This will often be useful
for writing minilanguages, (for example, in run control files for Python
applications) or for parsing quoted strings.
The shlex
module defines the following functions:
- shlex.split(s, comments=False, posix=True)¶
Split the string s using shell-like syntax. If comments is
False
(the default), the parsing of comments in the given string will be disabled (setting thecommenters
attribute of theshlex
instance to the empty string). This function operates in POSIX mode by default, but uses non-POSIX mode if the posix argument is false.Changed in version 3.12: Passing
None
for s argument now raises an exception, rather than readingsys.stdin
.
- shlex.join(split_command)¶
Concatenate the tokens of the list split_command and return a string. This function is the inverse of
split()
.>>> from shlex import join >>> print(join(['echo', '-n', 'Multiple words'])) echo -n 'Multiple words'
The returned value is shell-escaped to protect against injection vulnerabilities (see
quote()
).Added in version 3.8.
- shlex.quote(s)¶
Return a shell-escaped version of the string s. The returned value is a string that can safely be used as one token in a shell command line, for cases where you cannot use a list.
Warning
The
shlex
module is only designed for Unix shells.The
quote()
function is not guaranteed to be correct on non-POSIX compliant shells or shells from other operating systems such as Windows. Executing commands quoted by this module on such shells can open up the possibility of a command injection vulnerability.Consider using functions that pass command arguments with lists such as
subprocess.run()
withshell=False
.This idiom would be unsafe:
>>> filename = 'somefile; rm -rf ~' >>> command = 'ls -l {}'.format(filename) >>> print(command) # executed by a shell: boom! ls -l somefile; rm -rf ~
quote()
lets you plug the security hole:>>> from shlex import quote >>> command = 'ls -l {}'.format(quote(filename)) >>> print(command) ls -l 'somefile; rm -rf ~' >>> remote_command = 'ssh home {}'.format(quote(command)) >>> print(remote_command) ssh home 'ls -l '"'"'somefile; rm -rf ~'"'"''
The quoting is compatible with UNIX shells and with
split()
:>>> from shlex import split >>> remote_command = split(remote_command) >>> remote_command ['ssh', 'home', "ls -l 'somefile; rm -rf ~'"] >>> command = split(remote_command[-1]) >>> command ['ls', '-l', 'somefile; rm -rf ~']
Added in version 3.3.
The shlex
module defines the following class:
- class shlex.shlex(instream=None, infile=None, posix=False, punctuation_chars=False)¶
A
shlex
instance or subclass instance is a lexical analyzer object. The initialization argument, if present, specifies where to read characters from. It must be a file-/stream-like object withread()
andreadline()
methods, or a string. If no argument is given, input will be taken fromsys.stdin
. The second optional argument is a filename string, which sets the initial value of theinfile
attribute. If the instream argument is omitted or equal tosys.stdin
, this second argument defaults to “stdin”. The posix argument defines the operational mode: when posix is not true (default), theshlex
instance will operate in compatibility mode. When operating in POSIX mode,shlex
will try to be as close as possible to the POSIX shell parsing rules. The punctuation_chars argument provides a way to make the behaviour even closer to how real shells parse. This can take a number of values: the default value,False
, preserves the behaviour seen under Python 3.5 and earlier. If set toTrue
, then parsing of the characters();<>|&
is changed: any run of these characters (considered punctuation characters) is returned as a single token. If set to a non-empty string of characters, those characters will be used as the punctuation characters. Any characters in thewordchars
attribute that appear in punctuation_chars will be removed fromwordchars
. See Improved Compatibility with Shells for more information. punctuation_chars can be set only uponshlex
instance creation and can’t be modified later.Changed in version 3.6: The punctuation_chars parameter was added.
See also
- Module
configparser
Parser for configuration files similar to the Windows
.ini
files.
shlex Objects¶
A shlex
instance has the following methods:
- shlex.get_token()¶
Return a token. If tokens have been stacked using
push_token()
, pop a token off the stack. Otherwise, read one from the input stream. If reading encounters an immediate end-of-file,eof
is returned (the empty string (''
) in non-POSIX mode, andNone
in POSIX mode).
- shlex.push_token(str)¶
Push the argument onto the token stack.
- shlex.read_token()¶
Read a raw token. Ignore the pushback stack, and do not interpret source requests. (This is not ordinarily a useful entry point, and is documented here only for the sake of completeness.)
- shlex.sourcehook(filename)¶
When
shlex
detects a source request (seesource
below) this method is given the following token as argument, and expected to return a tuple consisting of a filename and an open file-like object.Normally, this method first strips any quotes off the argument. If the result is an absolute pathname, or there was no previous source request in effect, or the previous source was a stream (such as
sys.stdin
), the result is left alone. Otherwise, if the result is a relative pathname, the directory part of the name of the file immediately before it on the source inclusion stack is prepended (this behavior is like the way the C preprocessor handles#include "file.h"
).The result of the manipulations is treated as a filename, and returned as the first component of the tuple, with
open()
called on it to yield the second component. (Note: this is the reverse of the order of arguments in instance initialization!)This hook is exposed so that you can use it to implement directory search paths, addition of file extensions, and other namespace hacks. There is no corresponding ‘close’ hook, but a shlex instance will call the
close()
method of the sourced input stream when it returns EOF.For more explicit control of source stacking, use the
push_source()
andpop_source()
methods.
- shlex.push_source(newstream, newfile=None)¶
Push an input source stream onto the input stack. If the filename argument is specified it will later be available for use in error messages. This is the same method used internally by the
sourcehook()
method.
- shlex.pop_source()¶
Pop the last-pushed input source from the input stack. This is the same method used internally when the lexer reaches EOF on a stacked input stream.
- shlex.error_leader(infile=None, lineno=None)¶
This method generates an error message leader in the format of a Unix C compiler error label; the format is
'"%s", line %d: '
, where the%s
is replaced with the name of the current source file and the%d
with the current input line number (the optional arguments can be used to override these).This convenience is provided to encourage
shlex
users to generate error messages in the standard, parseable format understood by Emacs and other Unix tools.
Instances of shlex
subclasses have some public instance
variables which either control lexical analysis or can be used for debugging:
- shlex.commenters¶
The string of characters that are recognized as comment beginners. All characters from the comment beginner to end of line are ignored. Includes just
'#'
by default.
- shlex.wordchars¶
The string of characters that will accumulate into multi-character tokens. By default, includes all ASCII alphanumerics and underscore. In POSIX mode, the accented characters in the Latin-1 set are also included. If
punctuation_chars
is not empty, the characters~-./*?=
, which can appear in filename specifications and command line parameters, will also be included in this attribute, and any characters which appear inpunctuation_chars
will be removed fromwordchars
if they are present there. Ifwhitespace_split
is set toTrue
, this will have no effect.
- shlex.whitespace¶
Characters that will be considered whitespace and skipped. Whitespace bounds tokens. By default, includes space, tab, linefeed and carriage-return.
- shlex.escape¶
Characters that will be considered as escape. This will be only used in POSIX mode, and includes just
'\'
by default.
- shlex.quotes¶
Characters that will be considered string quotes. The token accumulates until the same quote is encountered again (thus, different quote types protect each other as in the shell.) By default, includes ASCII single and double quotes.
- shlex.escapedquotes¶
Characters in
quotes
that will interpret escape characters defined inescape
. This is only used in POSIX mode, and includes just'"'
by default.
- shlex.whitespace_split¶
If
True
, tokens will only be split in whitespaces. This is useful, for example, for parsing command lines withshlex
, getting tokens in a similar way to shell arguments. When used in combination withpunctuation_chars
, tokens will be split on whitespace in addition to those characters.Changed in version 3.8: The
punctuation_chars
attribute was made compatible with thewhitespace_split
attribute.
- shlex.infile¶
The name of the current input file, as initially set at class instantiation time or stacked by later source requests. It may be useful to examine this when constructing error messages.
- shlex.source¶
This attribute is
None
by default. If you assign a string to it, that string will be recognized as a lexical-level inclusion request similar to thesource
keyword in various shells. That is, the immediately following token will be opened as a filename and input will be taken from that stream until EOF, at which point theclose()
method of that stream will be called and the input source will again become the original input stream. Source requests may be stacked any number of levels deep.
- shlex.debug¶
If this attribute is numeric and
1
or more, ashlex
instance will print verbose progress output on its behavior. If you need to use this, you can read the module source code to learn the details.
- shlex.lineno¶
Source line number (count of newlines seen so far plus one).
- shlex.token¶
The token buffer. It may be useful to examine this when catching exceptions.
- shlex.eof¶
Token used to determine end of file. This will be set to the empty string (
''
), in non-POSIX mode, and toNone
in POSIX mode.
- shlex.punctuation_chars¶
A read-only property. Characters that will be considered punctuation. Runs of punctuation characters will be returned as a single token. However, note that no semantic validity checking will be performed: for example, ‘>>>’ could be returned as a token, even though it may not be recognised as such by shells.
Added in version 3.6.
Parsing Rules¶
When operating in non-POSIX mode, shlex
will try to obey the
following rules.
Quote characters are not recognized within words (
Do"Not"Separate
is parsed as the single wordDo"Not"Separate
);Escape characters are not recognized;
Enclosing characters in quotes preserve the literal value of all characters within the quotes;
Closing quotes separate words (
"Do"Separate
is parsed as"Do"
andSeparate
);If
whitespace_split
isFalse
, any character not declared to be a word character, whitespace, or a quote will be returned as a single-character token. If it isTrue
,shlex
will only split words in whitespaces;EOF is signaled with an empty string (
''
);It’s not possible to parse empty strings, even if quoted.
When operating in POSIX mode, shlex
will try to obey the
following parsing rules.
Quotes are stripped out, and do not separate words (
"Do"Not"Separate"
is parsed as the single wordDoNotSeparate
);Non-quoted escape characters (e.g.
'\'
) preserve the literal value of the next character that follows;Enclosing characters in quotes which are not part of
escapedquotes
(e.g."'"
) preserve the literal value of all characters within the quotes;Enclosing characters in quotes which are part of
escapedquotes
(e.g.'"'
) preserves the literal value of all characters within the quotes, with the exception of the characters mentioned inescape
. The escape characters retain their special meaning only when followed by the quote in use, or the escape character itself. Otherwise the escape character will be considered a normal character.EOF is signaled with a
None
value;Quoted empty strings (
''
) are allowed.
Improved Compatibility with Shells¶
Added in version 3.6.
The shlex
class provides compatibility with the parsing performed by
common Unix shells like bash
, dash
, and sh
. To take advantage of
this compatibility, specify the punctuation_chars
argument in the
constructor. This defaults to False
, which preserves pre-3.6 behaviour.
However, if it is set to True
, then parsing of the characters ();<>|&
is changed: any run of these characters is returned as a single token. While
this is short of a full parser for shells (which would be out of scope for the
standard library, given the multiplicity of shells out there), it does allow
you to perform processing of command lines more easily than you could
otherwise. To illustrate, you can see the difference in the following snippet:
>>> import shlex
>>> text = "a && b; c && d || e; f >'abc'; (def \"ghi\")"
>>> s = shlex.shlex(text, posix=True)
>>> s.whitespace_split = True
>>> list(s)
['a', '&&', 'b;', 'c', '&&', 'd', '||', 'e;', 'f', '>abc;', '(def', 'ghi)']
>>> s = shlex.shlex(text, posix=True, punctuation_chars=True)
>>> s.whitespace_split = True
>>> list(s)
['a', '&&', 'b', ';', 'c', '&&', 'd', '||', 'e', ';', 'f', '>', 'abc', ';',
'(', 'def', 'ghi', ')']
Of course, tokens will be returned which are not valid for shells, and you’ll need to implement your own error checks on the returned tokens.
Instead of passing True
as the value for the punctuation_chars parameter,
you can pass a string with specific characters, which will be used to determine
which characters constitute punctuation. For example:
>>> import shlex
>>> s = shlex.shlex("a && b || c", punctuation_chars="|")
>>> list(s)
['a', '&', '&', 'b', '||', 'c']
Note
When punctuation_chars
is specified, the wordchars
attribute is augmented with the characters ~-./*?=
. That is because these
characters can appear in file names (including wildcards) and command-line
arguments (e.g. --color=auto
). Hence:
>>> import shlex
>>> s = shlex.shlex('~/a && b-c --color=auto || d *.py?',
... punctuation_chars=True)
>>> list(s)
['~/a', '&&', 'b-c', '--color=auto', '||', 'd', '*.py?']
However, to match the shell as closely as possible, it is recommended to
always use posix
and whitespace_split
when using
punctuation_chars
, which will negate
wordchars
entirely.
For best effect, punctuation_chars
should be set in conjunction with
posix=True
. (Note that posix=False
is the default for
shlex
.)


Unix-specific services

Unix-specific services¶
The modules described in this chapter provide interfaces to features that are unique to the Unix operating system, or in some cases to some or many variants of it. Here’s an overview:
shlex
— Simple lexical analysisposix
— The most common POSIX system callspwd
— The password databasegrp
— The group databasetermios
— POSIX style tty controltty
— Terminal control functionspty
— Pseudo-terminal utilitiesfcntl
— Thefcntl
andioctl
system callsresource
— Resource usage informationsyslog
— Unix syslog library routines


— Sound-playing interface for Windows

winsound
— Sound-playing interface for Windows¶
The winsound
module provides access to the basic sound-playing machinery
provided by Windows platforms. It includes functions and several constants.
Availability: Windows.
- winsound.Beep(frequency, duration)¶
Beep the PC’s speaker. The frequency parameter specifies frequency, in hertz, of the sound, and must be in the range 37 through 32,767. The duration parameter specifies the number of milliseconds the sound should last. If the system is not able to beep the speaker,
RuntimeError
is raised.
- winsound.PlaySound(sound, flags)¶
Call the underlying
PlaySound()
function from the Platform API. The sound parameter may be a filename, a system sound alias, audio data as a bytes-like object, orNone
. Its interpretation depends on the value of flags, which can be a bitwise ORed combination of the constants described below. If the sound parameter isNone
, any currently playing waveform sound is stopped. If the system indicates an error,RuntimeError
is raised.
- winsound.MessageBeep(type=MB_OK)¶
Call the underlying
MessageBeep()
function from the Platform API. This plays a sound as specified in the registry. The type argument specifies which sound to play; possible values are-1
,MB_ICONASTERISK
,MB_ICONEXCLAMATION
,MB_ICONHAND
,MB_ICONQUESTION
, andMB_OK
, all described below. The value-1
produces a “simple beep”; this is the final fallback if a sound cannot be played otherwise. If the system indicates an error,RuntimeError
is raised.
- winsound.SND_ALIAS¶
The sound parameter is a sound association name from the registry. If the registry contains no such name, play the system default sound unless
SND_NODEFAULT
is also specified. If no default sound is registered, raiseRuntimeError
. Do not use withSND_FILENAME
.All Win32 systems support at least the following; most systems support many more:
PlaySound()
nameCorresponding Control Panel Sound name
'SystemAsterisk'
Asterisk
'SystemExclamation'
Exclamation
'SystemExit'
Exit Windows
'SystemHand'
Critical Stop
'SystemQuestion'
Question
For example:
import winsound # Play Windows exit sound. winsound.PlaySound("SystemExit", winsound.SND_ALIAS) # Probably play Windows default sound, if any is registered (because # "*" probably isn't the registered name of any sound). winsound.PlaySound("*", winsound.SND_ALIAS)
- winsound.SND_LOOP¶
Play the sound repeatedly. The
SND_ASYNC
flag must also be used to avoid blocking. Cannot be used withSND_MEMORY
.
- winsound.SND_MEMORY¶
The sound parameter to
PlaySound()
is a memory image of a WAV file, as a bytes-like object.Note
This module does not support playing from a memory image asynchronously, so a combination of this flag and
SND_ASYNC
will raiseRuntimeError
.
- winsound.SND_PURGE¶
Stop playing all instances of the specified sound.
Note
This flag is not supported on modern Windows platforms.
- winsound.SND_ASYNC¶
Return immediately, allowing sounds to play asynchronously.
- winsound.SND_NODEFAULT¶
If the specified sound cannot be found, do not play the system default sound.
- winsound.SND_NOSTOP¶
Do not interrupt sounds currently playing.
- winsound.SND_NOWAIT¶
Return immediately if the sound driver is busy.
Note
This flag is not supported on modern Windows platforms.
- winsound.SND_APPLICATION¶
The sound parameter is an application-specific alias in the registry. This flag can be combined with the
SND_ALIAS
flag to specify an application-defined sound alias.
- winsound.SND_SENTRY¶
Triggers a SoundSentry event when the sound is played.
Added in version 3.14.
- winsound.SND_SYNC¶
The sound is played synchronously. This is the default behavior.
Added in version 3.14.
- winsound.SND_SYSTEM¶
Assign the sound to the audio session for system notification sounds.
Added in version 3.14.
- winsound.MB_ICONASTERISK¶
Play the
SystemDefault
sound.
- winsound.MB_ICONEXCLAMATION¶
Play the
SystemExclamation
sound.
- winsound.MB_ICONHAND¶
Play the
SystemHand
sound.
- winsound.MB_ICONQUESTION¶
Play the
SystemQuestion
sound.
- winsound.MB_OK¶
Play the
SystemDefault
sound.
- winsound.MB_ICONERROR¶
Play the
SystemHand
sound.Added in version 3.14.
- winsound.MB_ICONINFORMATION¶
Play the
SystemDefault
sound.Added in version 3.14.
- winsound.MB_ICONSTOP¶
Play the
SystemHand
sound.Added in version 3.14.
- winsound.MB_ICONWARNING¶
Play the
SystemExclamation
sound.Added in version 3.14.


— Windows registry access

winreg
— Windows registry access¶
These functions expose the Windows registry API to Python. Instead of using an integer as the registry handle, a handle object is used to ensure that the handles are closed correctly, even if the programmer neglects to explicitly close them.
Availability: Windows.
Changed in version 3.3: Several functions in this module used to raise a
WindowsError
, which is now an alias of OSError
.
Functions¶
This module offers the following functions:
- winreg.CloseKey(hkey)¶
Closes a previously opened registry key. The hkey argument specifies a previously opened key.
Note
If hkey is not closed using this method (or via
hkey.Close()
), it is closed when the hkey object is destroyed by Python.
- winreg.ConnectRegistry(computer_name, key)¶
Establishes a connection to a predefined registry handle on another computer, and returns a handle object.
computer_name is the name of the remote computer, of the form
r"\\computername"
. IfNone
, the local computer is used.key is the predefined handle to connect to.
The return value is the handle of the opened key. If the function fails, an
OSError
exception is raised.Raises an auditing event
winreg.ConnectRegistry
with argumentscomputer_name
,key
.Changed in version 3.3: See above.
- winreg.CreateKey(key, sub_key)¶
Creates or opens the specified key, returning a handle object.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that names the key this method opens or creates.
If key is one of the predefined keys, sub_key may be
None
. In that case, the handle returned is the same key handle passed in to the function.If the key already exists, this function opens the existing key.
The return value is the handle of the opened key. If the function fails, an
OSError
exception is raised.Raises an auditing event
winreg.CreateKey
with argumentskey
,sub_key
,access
.Raises an auditing event
winreg.OpenKey/result
with argumentkey
.Changed in version 3.3: See above.
- winreg.CreateKeyEx(key, sub_key, reserved=0, access=KEY_WRITE)¶
Creates or opens the specified key, returning a handle object.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that names the key this method opens or creates.
reserved is a reserved integer, and must be zero. The default is zero.
access is an integer that specifies an access mask that describes the desired security access for the key. Default is
KEY_WRITE
. See Access Rights for other allowed values.If key is one of the predefined keys, sub_key may be
None
. In that case, the handle returned is the same key handle passed in to the function.If the key already exists, this function opens the existing key.
The return value is the handle of the opened key. If the function fails, an
OSError
exception is raised.Raises an auditing event
winreg.CreateKey
with argumentskey
,sub_key
,access
.Raises an auditing event
winreg.OpenKey/result
with argumentkey
.Added in version 3.2.
Changed in version 3.3: See above.
- winreg.DeleteKey(key, sub_key)¶
Deletes the specified key.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that must be a subkey of the key identified by the key parameter. This value must not be
None
, and the key may not have subkeys.This method can not delete keys with subkeys.
If the method succeeds, the entire key, including all of its values, is removed. If the method fails, an
OSError
exception is raised.Raises an auditing event
winreg.DeleteKey
with argumentskey
,sub_key
,access
.Changed in version 3.3: See above.
- winreg.DeleteKeyEx(key, sub_key, access=KEY_WOW64_64KEY, reserved=0)¶
Deletes the specified key.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that must be a subkey of the key identified by the key parameter. This value must not be
None
, and the key may not have subkeys.reserved is a reserved integer, and must be zero. The default is zero.
access is an integer that specifies an access mask that describes the desired security access for the key. Default is
KEY_WOW64_64KEY
. On 32-bit Windows, the WOW64 constants are ignored. See Access Rights for other allowed values.This method can not delete keys with subkeys.
If the method succeeds, the entire key, including all of its values, is removed. If the method fails, an
OSError
exception is raised.On unsupported Windows versions,
NotImplementedError
is raised.Raises an auditing event
winreg.DeleteKey
with argumentskey
,sub_key
,access
.Added in version 3.2.
Changed in version 3.3: See above.
- winreg.DeleteValue(key, value)¶
Removes a named value from a registry key.
key is an already open key, or one of the predefined HKEY_* constants.
value is a string that identifies the value to remove.
Raises an auditing event
winreg.DeleteValue
with argumentskey
,value
.
- winreg.EnumKey(key, index)¶
Enumerates subkeys of an open registry key, returning a string.
key is an already open key, or one of the predefined HKEY_* constants.
index is an integer that identifies the index of the key to retrieve.
The function retrieves the name of one subkey each time it is called. It is typically called repeatedly until an
OSError
exception is raised, indicating, no more values are available.Raises an auditing event
winreg.EnumKey
with argumentskey
,index
.Changed in version 3.3: See above.
- winreg.EnumValue(key, index)¶
Enumerates values of an open registry key, returning a tuple.
key is an already open key, or one of the predefined HKEY_* constants.
index is an integer that identifies the index of the value to retrieve.
The function retrieves the name of one subkey each time it is called. It is typically called repeatedly, until an
OSError
exception is raised, indicating no more values.The result is a tuple of 3 items:
Index
Meaning
0
A string that identifies the value name
1
An object that holds the value data, and whose type depends on the underlying registry type
2
An integer that identifies the type of the value data (see table in docs for
SetValueEx()
)Raises an auditing event
winreg.EnumValue
with argumentskey
,index
.Changed in version 3.3: See above.
- winreg.ExpandEnvironmentStrings(str)¶
Expands environment variable placeholders
%NAME%
in strings likeREG_EXPAND_SZ
:>>> ExpandEnvironmentStrings('%windir%') 'C:\\Windows'
Raises an auditing event
winreg.ExpandEnvironmentStrings
with argumentstr
.
- winreg.FlushKey(key)¶
Writes all the attributes of a key to the registry.
key is an already open key, or one of the predefined HKEY_* constants.
It is not necessary to call
FlushKey()
to change a key. Registry changes are flushed to disk by the registry using its lazy flusher. Registry changes are also flushed to disk at system shutdown. UnlikeCloseKey()
, theFlushKey()
method returns only when all the data has been written to the registry. An application should only callFlushKey()
if it requires absolute certainty that registry changes are on disk.Note
If you don’t know whether a
FlushKey()
call is required, it probably isn’t.
- winreg.LoadKey(key, sub_key, file_name)¶
Creates a subkey under the specified key and stores registration information from a specified file into that subkey.
key is a handle returned by
ConnectRegistry()
or one of the constantsHKEY_USERS
orHKEY_LOCAL_MACHINE
.sub_key is a string that identifies the subkey to load.
file_name is the name of the file to load registry data from. This file must have been created with the
SaveKey()
function. Under the file allocation table (FAT) file system, the filename may not have an extension.A call to
LoadKey()
fails if the calling process does not have theSE_RESTORE_PRIVILEGE
privilege. Note that privileges are different from permissions – see the RegLoadKey documentation for more details.If key is a handle returned by
ConnectRegistry()
, then the path specified in file_name is relative to the remote computer.Raises an auditing event
winreg.LoadKey
with argumentskey
,sub_key
,file_name
.
- winreg.OpenKey(key, sub_key, reserved=0, access=KEY_READ)¶
- winreg.OpenKeyEx(key, sub_key, reserved=0, access=KEY_READ)¶
Opens the specified key, returning a handle object.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that identifies the sub_key to open.
reserved is a reserved integer, and must be zero. The default is zero.
access is an integer that specifies an access mask that describes the desired security access for the key. Default is
KEY_READ
. See Access Rights for other allowed values.The result is a new handle to the specified key.
If the function fails,
OSError
is raised.Raises an auditing event
winreg.OpenKey
with argumentskey
,sub_key
,access
.Raises an auditing event
winreg.OpenKey/result
with argumentkey
.Changed in version 3.2: Allow the use of named arguments.
Changed in version 3.3: See above.
- winreg.QueryInfoKey(key)¶
Returns information about a key, as a tuple.
key is an already open key, or one of the predefined HKEY_* constants.
The result is a tuple of 3 items:
Index
Meaning
0
An integer giving the number of sub keys this key has.
1
An integer giving the number of values this key has.
2
An integer giving when the key was last modified (if available) as 100’s of nanoseconds since Jan 1, 1601.
Raises an auditing event
winreg.QueryInfoKey
with argumentkey
.
- winreg.QueryValue(key, sub_key)¶
Retrieves the unnamed value for a key, as a string.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that holds the name of the subkey with which the value is associated. If this parameter is
None
or empty, the function retrieves the value set by theSetValue()
method for the key identified by key.Values in the registry have name, type, and data components. This method retrieves the data for a key’s first value that has a
NULL
name. But the underlying API call doesn’t return the type, so always useQueryValueEx()
if possible.Raises an auditing event
winreg.QueryValue
with argumentskey
,sub_key
,value_name
.
- winreg.QueryValueEx(key, value_name)¶
Retrieves the type and data for a specified value name associated with an open registry key.
key is an already open key, or one of the predefined HKEY_* constants.
value_name is a string indicating the value to query.
The result is a tuple of 2 items:
Index
Meaning
0
The value of the registry item.
1
An integer giving the registry type for this value (see table in docs for
SetValueEx()
)Raises an auditing event
winreg.QueryValue
with argumentskey
,sub_key
,value_name
.
- winreg.SaveKey(key, file_name)¶
Saves the specified key, and all its subkeys to the specified file.
key is an already open key, or one of the predefined HKEY_* constants.
file_name is the name of the file to save registry data to. This file cannot already exist. If this filename includes an extension, it cannot be used on file allocation table (FAT) file systems by the
LoadKey()
method.If key represents a key on a remote computer, the path described by file_name is relative to the remote computer. The caller of this method must possess the SeBackupPrivilege security privilege. Note that privileges are different than permissions – see the Conflicts Between User Rights and Permissions documentation for more details.
This function passes
NULL
for security_attributes to the API.Raises an auditing event
winreg.SaveKey
with argumentskey
,file_name
.
- winreg.SetValue(key, sub_key, type, value)¶
Associates a value with a specified key.
key is an already open key, or one of the predefined HKEY_* constants.
sub_key is a string that names the subkey with which the value is associated.
type is an integer that specifies the type of the data. Currently this must be
REG_SZ
, meaning only strings are supported. Use theSetValueEx()
function for support for other data types.value is a string that specifies the new value.
If the key specified by the sub_key parameter does not exist, the SetValue function creates it.
Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the configuration registry. This helps the registry perform efficiently.
The key identified by the key parameter must have been opened with
KEY_SET_VALUE
access.Raises an auditing event
winreg.SetValue
with argumentskey
,sub_key
,type
,value
.
- winreg.SetValueEx(key, value_name, reserved, type, value)¶
Stores data in the value field of an open registry key.
key is an already open key, or one of the predefined HKEY_* constants.
value_name is a string that names the subkey with which the value is associated.
reserved can be anything – zero is always passed to the API.
type is an integer that specifies the type of the data. See Value Types for the available types.
value is a string that specifies the new value.
This method can also set additional value and type information for the specified key. The key identified by the key parameter must have been opened with
KEY_SET_VALUE
access.To open the key, use the
CreateKey()
orOpenKey()
methods.Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the configuration registry. This helps the registry perform efficiently.
Raises an auditing event
winreg.SetValue
with argumentskey
,sub_key
,type
,value
.
- winreg.DisableReflectionKey(key)¶
Disables registry reflection for 32-bit processes running on a 64-bit operating system.
key is an already open key, or one of the predefined HKEY_* constants.
Will generally raise
NotImplementedError
if executed on a 32-bit operating system.If the key is not on the reflection list, the function succeeds but has no effect. Disabling reflection for a key does not affect reflection of any subkeys.
Raises an auditing event
winreg.DisableReflectionKey
with argumentkey
.
- winreg.EnableReflectionKey(key)¶
Restores registry reflection for the specified disabled key.
key is an already open key, or one of the predefined HKEY_* constants.
Will generally raise
NotImplementedError
if executed on a 32-bit operating system.Restoring reflection for a key does not affect reflection of any subkeys.
Raises an auditing event
winreg.EnableReflectionKey
with argumentkey
.
- winreg.QueryReflectionKey(key)¶
Determines the reflection state for the specified key.
key is an already open key, or one of the predefined HKEY_* constants.
Returns
True
if reflection is disabled.Will generally raise
NotImplementedError
if executed on a 32-bit operating system.Raises an auditing event
winreg.QueryReflectionKey
with argumentkey
.
Constants¶
The following constants are defined for use in many winreg
functions.
HKEY_* Constants¶
- winreg.HKEY_CLASSES_ROOT¶
Registry entries subordinate to this key define types (or classes) of documents and the properties associated with those types. Shell and COM applications use the information stored under this key.
- winreg.HKEY_CURRENT_USER¶
Registry entries subordinate to this key define the preferences of the current user. These preferences include the settings of environment variables, data about program groups, colors, printers, network connections, and application preferences.
- winreg.HKEY_LOCAL_MACHINE¶
Registry entries subordinate to this key define the physical state of the computer, including data about the bus type, system memory, and installed hardware and software.
- winreg.HKEY_USERS¶
Registry entries subordinate to this key define the default user configuration for new users on the local computer and the user configuration for the current user.
- winreg.HKEY_PERFORMANCE_DATA¶
Registry entries subordinate to this key allow you to access performance data. The data is not actually stored in the registry; the registry functions cause the system to collect the data from its source.
- winreg.HKEY_CURRENT_CONFIG¶
Contains information about the current hardware profile of the local computer system.
- winreg.HKEY_DYN_DATA¶
This key is not used in versions of Windows after 98.
Access Rights¶
For more information, see Registry Key Security and Access.
- winreg.KEY_ALL_ACCESS¶
Combines the STANDARD_RIGHTS_REQUIRED,
KEY_QUERY_VALUE
,KEY_SET_VALUE
,KEY_CREATE_SUB_KEY
,KEY_ENUMERATE_SUB_KEYS
,KEY_NOTIFY
, andKEY_CREATE_LINK
access rights.
- winreg.KEY_WRITE¶
Combines the STANDARD_RIGHTS_WRITE,
KEY_SET_VALUE
, andKEY_CREATE_SUB_KEY
access rights.
- winreg.KEY_READ¶
Combines the STANDARD_RIGHTS_READ,
KEY_QUERY_VALUE
,KEY_ENUMERATE_SUB_KEYS
, andKEY_NOTIFY
values.
- winreg.KEY_QUERY_VALUE¶
Required to query the values of a registry key.
- winreg.KEY_SET_VALUE¶
Required to create, delete, or set a registry value.
- winreg.KEY_CREATE_SUB_KEY¶
Required to create a subkey of a registry key.
- winreg.KEY_ENUMERATE_SUB_KEYS¶
Required to enumerate the subkeys of a registry key.
- winreg.KEY_NOTIFY¶
Required to request change notifications for a registry key or for subkeys of a registry key.
- winreg.KEY_CREATE_LINK¶
Reserved for system use.
64-bit Specific¶
For more information, see Accessing an Alternate Registry View.
- winreg.KEY_WOW64_64KEY¶
Indicates that an application on 64-bit Windows should operate on the 64-bit registry view. On 32-bit Windows, this constant is ignored.
- winreg.KEY_WOW64_32KEY¶
Indicates that an application on 64-bit Windows should operate on the 32-bit registry view. On 32-bit Windows, this constant is ignored.
Value Types¶
For more information, see Registry Value Types.
- winreg.REG_BINARY¶
Binary data in any form.
- winreg.REG_DWORD¶
32-bit number.
- winreg.REG_DWORD_BIG_ENDIAN¶
A 32-bit number in big-endian format.
- winreg.REG_EXPAND_SZ¶
Null-terminated string containing references to environment variables (
%PATH%
).
- winreg.REG_LINK¶
A Unicode symbolic link.
- winreg.REG_MULTI_SZ¶
A sequence of null-terminated strings, terminated by two null characters. (Python handles this termination automatically.)
- winreg.REG_NONE¶
No defined value type.
- winreg.REG_QWORD¶
A 64-bit number.
Added in version 3.6.
- winreg.REG_QWORD_LITTLE_ENDIAN¶
A 64-bit number in little-endian format. Equivalent to
REG_QWORD
.Added in version 3.6.
- winreg.REG_RESOURCE_LIST¶
A device-driver resource list.
- winreg.REG_FULL_RESOURCE_DESCRIPTOR¶
A hardware setting.
- winreg.REG_RESOURCE_REQUIREMENTS_LIST¶
A hardware resource list.
- winreg.REG_SZ¶
A null-terminated string.
Registry Handle Objects¶
This object wraps a Windows HKEY object, automatically closing it when the
object is destroyed. To guarantee cleanup, you can call either the
Close()
method on the object, or the CloseKey()
function.
All registry functions in this module return one of these objects.
All registry functions in this module which accept a handle object also accept an integer, however, use of the handle object is encouraged.
Handle objects provide semantics for __bool__()
– thus
if handle:
print("Yes")
will print Yes
if the handle is currently valid (has not been closed or
detached).
Handle objects can be converted to an integer (e.g., using the built-in
int()
function), in which case the underlying Windows handle value is
returned. You can also use the Detach()
method to return the
integer handle, and also disconnect the Windows handle from the handle object.
- PyHKEY.Close()¶
Closes the underlying Windows handle.
If the handle is already closed, no error is raised.
- PyHKEY.Detach()¶
Detaches the Windows handle from the handle object.
The result is an integer that holds the value of the handle before it is detached. If the handle is already detached or closed, this will return zero.
After calling this function, the handle is effectively invalidated, but the handle is not closed. You would call this function when you need the underlying Win32 handle to exist beyond the lifetime of the handle object.
Raises an auditing event
winreg.PyHKEY.Detach
with argumentkey
.
- PyHKEY.__enter__()¶
- PyHKEY.__exit__(*exc_info)¶
The HKEY object implements
__enter__()
and__exit__()
and thus supports the context protocol for thewith
statement:with OpenKey(HKEY_LOCAL_MACHINE, "foo") as key: ... # work with key
will automatically close key when control leaves the
with
block.


msvcrt
— Useful routines from the MS VC++ runtime¶
These functions provide access to some useful capabilities on Windows platforms.
Some higher-level modules use these functions to build the Windows
implementations of their services. For example, the getpass
module uses
this in the implementation of the getpass()
function.
Further documentation on these functions can be found in the Platform API documentation.
The module implements both the normal and wide char variants of the console I/O api. The normal API deals only with ASCII characters and is of limited use for internationalized applications. The wide char API should be used where ever possible.
Availability: Windows.
File Operations¶
- msvcrt.locking(fd, mode, nbytes)¶
Lock part of a file based on file descriptor fd from the C runtime. Raises
OSError
on failure. The locked region of the file extends from the current file position for nbytes bytes, and may continue beyond the end of the file. mode must be one of theLK_*
constants listed below. Multiple regions in a file may be locked at the same time, but may not overlap. Adjacent regions are not merged; they must be unlocked individually.Raises an auditing event
msvcrt.locking
with argumentsfd
,mode
,nbytes
.
- msvcrt.LK_LOCK¶
- msvcrt.LK_RLCK¶
Locks the specified bytes. If the bytes cannot be locked, the program immediately tries again after 1 second. If, after 10 attempts, the bytes cannot be locked,
OSError
is raised.
- msvcrt.LK_NBLCK¶
- msvcrt.LK_NBRLCK¶
Locks the specified bytes. If the bytes cannot be locked,
OSError
is raised.
- msvcrt.LK_UNLCK¶
Unlocks the specified bytes, which must have been previously locked.
- msvcrt.setmode(fd, flags)¶
Set the line-end translation mode for the file descriptor fd. To set it to text mode, flags should be
os.O_TEXT
; for binary, it should beos.O_BINARY
.
- msvcrt.open_osfhandle(handle, flags)¶
Create a C runtime file descriptor from the file handle handle. The flags parameter should be a bitwise OR of
os.O_APPEND
,os.O_RDONLY
,os.O_TEXT
andos.O_NOINHERIT
. The returned file descriptor may be used as a parameter toos.fdopen()
to create a file object.The file descriptor is inheritable by default. Pass
os.O_NOINHERIT
flag to make it non inheritable.Raises an auditing event
msvcrt.open_osfhandle
with argumentshandle
,flags
.
- msvcrt.get_osfhandle(fd)¶
Return the file handle for the file descriptor fd. Raises
OSError
if fd is not recognized.Raises an auditing event
msvcrt.get_osfhandle
with argumentfd
.
Console I/O¶
- msvcrt.kbhit()¶
Returns a nonzero value if a keypress is waiting to be read. Otherwise, return 0.
- msvcrt.getch()¶
Read a keypress and return the resulting character as a byte string. Nothing is echoed to the console. This call will block if a keypress is not already available, but will not wait for Enter to be pressed. If the pressed key was a special function key, this will return
'\000'
or'\xe0'
; the next call will return the keycode. The Control-C keypress cannot be read with this function.
- msvcrt.getche()¶
Similar to
getch()
, but the keypress will be echoed if it represents a printable character.
- msvcrt.putch(char)¶
Print the byte string char to the console without buffering.
Other Functions¶
- msvcrt.heapmin()¶
Force the
malloc()
heap to clean itself up and return unused blocks to the operating system. On failure, this raisesOSError
.
- msvcrt.set_error_mode(mode)¶
Changes the location where the C runtime writes an error message for an error that might end the program. mode must be one of the
OUT_*
constants listed below orREPORT_ERRMODE
. Returns the old setting or -1 if an error occurs. Only available in debug build of Python.
- msvcrt.OUT_TO_DEFAULT¶
Error sink is determined by the app’s type. Only available in debug build of Python.
- msvcrt.OUT_TO_STDERR¶
Error sink is a standard error. Only available in debug build of Python.
- msvcrt.OUT_TO_MSGBOX¶
Error sink is a message box. Only available in debug build of Python.
- msvcrt.REPORT_ERRMODE¶
Report the current error mode value. Only available in debug build of Python.
- msvcrt.CrtSetReportMode(type, mode)¶
Specifies the destination or destinations for a specific report type generated by
_CrtDbgReport()
in the MS VC++ runtime. type must be one of theCRT_*
constants listed below. mode must be one of theCRTDBG_*
constants listed below. Only available in debug build of Python.
- msvcrt.CrtSetReportFile(type, file)¶
After you use
CrtSetReportMode()
to specifyCRTDBG_MODE_FILE
, you can specify the file handle to receive the message text. type must be one of theCRT_*
constants listed below. file should be the file handle your want specified. Only available in debug build of Python.
- msvcrt.CRT_WARN¶
Warnings, messages, and information that doesn’t need immediate attention.
- msvcrt.CRT_ERROR¶
Errors, unrecoverable problems, and issues that require immediate attention.
- msvcrt.CRT_ASSERT¶
Assertion failures.
- msvcrt.CRTDBG_MODE_DEBUG¶
Writes the message to the debugger’s output window.
- msvcrt.CRTDBG_MODE_FILE¶
Writes the message to a user-supplied file handle.
CrtSetReportFile()
should be called to define the specific file or stream to use as the destination.
- msvcrt.CRTDBG_MODE_WNDW¶
Creates a message box to display the message along with the
Abort
,Retry
, andIgnore
buttons.
- msvcrt.CRTDBG_REPORT_MODE¶
Returns current mode for the specified type.
- msvcrt.CRT_ASSEMBLY_VERSION¶
The CRT Assembly version, from the
crtassem.h
header file.
- msvcrt.VC_ASSEMBLY_PUBLICKEYTOKEN¶
The VC Assembly public key token, from the
crtassem.h
header file.
- msvcrt.LIBRARIES_ASSEMBLY_NAME_PREFIX¶
The Libraries Assembly name prefix, from the
crtassem.h
header file.


MS Windows Specific Services

pickletools — Tools for pickle developers
pickletools
msvcrt — Useful routines from the MS VC++ runtime
msvcrt
This chapter describes modules that are only available on MS Windows platforms.
winreg
winsound


— Tools for pickle developers

pickletools
— Tools for pickle developers¶
Source code: Lib/pickletools.py
This module contains various constants relating to the intimate details of the
pickle
module, some lengthy comments about the implementation, and a
few useful functions for analyzing pickled data. The contents of this module
are useful for Python core developers who are working on the pickle
;
ordinary users of the pickle
module probably won’t find the
pickletools
module relevant.
Command-line usage¶
Added in version 3.2.
When invoked from the command line, python -m pickletools
will
disassemble the contents of one or more pickle files. Note that if
you want to see the Python object stored in the pickle rather than the
details of pickle format, you may want to use -m pickle
instead.
However, when the pickle file that you want to examine comes from an
untrusted source, -m pickletools
is a safer option because it does
not execute pickle bytecode.
For example, with a tuple (1, 2)
pickled in file x.pickle
:
$ python -m pickle x.pickle
(1, 2)
$ python -m pickletools x.pickle
0: \x80 PROTO 3
2: K BININT1 1
4: K BININT1 2
6: \x86 TUPLE2
7: q BINPUT 0
9: . STOP
highest protocol among opcodes = 2
Command-line options¶
- -a, --annotate¶
Annotate each line with a short opcode description.
- -o, --output=<file>¶
Name of a file where the output should be written.
- -l, --indentlevel=<num>¶
The number of blanks by which to indent a new MARK level.
- -m, --memo¶
When multiple objects are disassembled, preserve memo between disassemblies.
- -p, --preamble=<preamble>¶
When more than one pickle file is specified, print given preamble before each disassembly.
- pickle_file¶
A pickle file to read, or
-
to indicate reading from standard input.
Programmatic interface¶
- pickletools.dis(pickle, out=None, memo=None, indentlevel=4, annotate=0)¶
Outputs a symbolic disassembly of the pickle to the file-like object out, defaulting to
sys.stdout
. pickle can be a string or a file-like object. memo can be a Python dictionary that will be used as the pickle’s memo; it can be used to perform disassemblies across multiple pickles created by the same pickler. Successive levels, indicated byMARK
opcodes in the stream, are indented by indentlevel spaces. If a nonzero value is given to annotate, each opcode in the output is annotated with a short description. The value of annotate is used as a hint for the column where annotation should start.Changed in version 3.2: Added the annotate parameter.
- pickletools.genops(pickle)¶
Provides an iterator over all of the opcodes in a pickle, returning a sequence of
(opcode, arg, pos)
triples. opcode is an instance of anOpcodeInfo
class; arg is the decoded value, as a Python object, of the opcode’s argument; pos is the position at which this opcode is located. pickle can be a string or a file-like object.
- pickletools.optimize(picklestring)¶
Returns a new equivalent pickle string after eliminating unused
PUT
opcodes. The optimized pickle is shorter, takes less transmission time, requires less storage space, and unpickles more efficiently.


— Disassembler for Python bytecode

dis
— Disassembler for Python bytecode¶
Source code: Lib/dis.py
The dis
module supports the analysis of CPython bytecode by
disassembling it. The CPython bytecode which this module takes as an input is
defined in the file Include/opcode.h
and used by the compiler and the
interpreter.
CPython implementation detail: Bytecode is an implementation detail of the CPython interpreter. No guarantees are made that bytecode will not be added, removed, or changed between versions of Python. Use of this module should not be considered to work across Python VMs or Python releases.
Changed in version 3.6: Use 2 bytes for each instruction. Previously the number of bytes varied by instruction.
Changed in version 3.10: The argument of jump, exception handling and loop instructions is now the instruction offset rather than the byte offset.
Changed in version 3.11: Some instructions are accompanied by one or more inline cache entries,
which take the form of CACHE
instructions. These instructions
are hidden by default, but can be shown by passing show_caches=True
to
any dis
utility. Furthermore, the interpreter now adapts the
bytecode to specialize it for different runtime conditions. The
adaptive bytecode can be shown by passing adaptive=True
.
Changed in version 3.12: The argument of a jump is the offset of the target instruction relative
to the instruction that appears immediately after the jump instruction’s
CACHE
entries.
As a consequence, the presence of the CACHE
instructions is
transparent for forward jumps but needs to be taken into account when
reasoning about backward jumps.
Changed in version 3.13: The output shows logical labels rather than instruction offsets
for jump targets and exception handlers. The -O
command line
option and the show_offsets
argument were added.
Example: Given the function myfunc()
:
def myfunc(alist):
return len(alist)
the following command can be used to display the disassembly of
myfunc()
:
>>> dis.dis(myfunc)
2 RESUME 0
3 LOAD_GLOBAL 1 (len + NULL)
LOAD_FAST_BORROW 0 (alist)
CALL 1
RETURN_VALUE
(The “2” is a line number).
Command-line interface¶
The dis
module can be invoked as a script from the command line:
python -m dis [-h] [-C] [-O] [-P] [-S] [infile]
The following options are accepted:
- -h, --help¶
Display usage and exit.
- -C, --show-caches¶
Show inline caches.
Added in version 3.13.
- -O, --show-offsets¶
Show offsets of instructions.
Added in version 3.13.
- -P, --show-positions¶
Show positions of instructions in the source code.
Added in version 3.14.
- -S, --specialized¶
Show specialized bytecode.
Added in version 3.14.
If infile
is specified, its disassembled code will be written to stdout.
Otherwise, disassembly is performed on compiled source code received from stdin.
Bytecode analysis¶
Added in version 3.4.
The bytecode analysis API allows pieces of Python code to be wrapped in a
Bytecode
object that provides easy access to details of the compiled
code.
- class dis.Bytecode(x, *, first_line=None, current_offset=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
Analyse the bytecode corresponding to a function, generator, asynchronous generator, coroutine, method, string of source code, or a code object (as returned by
compile()
).This is a convenience wrapper around many of the functions listed below, most notably
get_instructions()
, as iterating over aBytecode
instance yields the bytecode operations asInstruction
instances.If first_line is not
None
, it indicates the line number that should be reported for the first source line in the disassembled code. Otherwise, the source line information (if any) is taken directly from the disassembled code object.If current_offset is not
None
, it refers to an instruction offset in the disassembled code. Setting this meansdis()
will display a “current instruction” marker against the specified opcode.If show_caches is
True
,dis()
will display inline cache entries used by the interpreter to specialize the bytecode.If adaptive is
True
,dis()
will display specialized bytecode that may be different from the original bytecode.If show_offsets is
True
,dis()
will include instruction offsets in the output.If show_positions is
True
,dis()
will include instruction source code positions in the output.- classmethod from_traceback(tb, *, show_caches=False)¶
Construct a
Bytecode
instance from the given traceback, setting current_offset to the instruction responsible for the exception.
- codeobj¶
The compiled code object.
- first_line¶
The first source line of the code object (if available)
- dis()¶
Return a formatted view of the bytecode operations (the same as printed by
dis.dis()
, but returned as a multi-line string).
- info()¶
Return a formatted multi-line string with detailed information about the code object, like
code_info()
.
Changed in version 3.7: This can now handle coroutine and asynchronous generator objects.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter
Changed in version 3.14: Added the show_positions parameter.
Example:
>>> bytecode = dis.Bytecode(myfunc)
>>> for instr in bytecode:
... print(instr.opname)
...
RESUME
LOAD_GLOBAL
LOAD_FAST_BORROW
CALL
RETURN_VALUE
Analysis functions¶
The dis
module also defines the following analysis functions that convert
the input directly to the desired output. They can be useful if only a single
operation is being performed, so the intermediate analysis object isn’t useful:
- dis.code_info(x)¶
Return a formatted multi-line string with detailed code object information for the supplied function, generator, asynchronous generator, coroutine, method, source code string or code object.
Note that the exact contents of code info strings are highly implementation dependent and they may change arbitrarily across Python VMs or Python releases.
Added in version 3.2.
Changed in version 3.7: This can now handle coroutine and asynchronous generator objects.
- dis.show_code(x, *, file=None)¶
Print detailed code object information for the supplied function, method, source code string or code object to file (or
sys.stdout
if file is not specified).This is a convenient shorthand for
print(code_info(x), file=file)
, intended for interactive exploration at the interpreter prompt.Added in version 3.2.
Changed in version 3.4: Added file parameter.
- dis.dis(x=None, *, file=None, depth=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
Disassemble the x object. x can denote either a module, a class, a method, a function, a generator, an asynchronous generator, a coroutine, a code object, a string of source code or a byte sequence of raw bytecode. For a module, it disassembles all functions. For a class, it disassembles all methods (including class and static methods). For a code object or sequence of raw bytecode, it prints one line per bytecode instruction. It also recursively disassembles nested code objects. These can include generator expressions, nested functions, the bodies of nested classes, and the code objects used for annotation scopes. Strings are first compiled to code objects with the
compile()
built-in function before being disassembled. If no object is provided, this function disassembles the last traceback.The disassembly is written as text to the supplied file argument if provided and to
sys.stdout
otherwise.The maximal depth of recursion is limited by depth unless it is
None
.depth=0
means no recursion.If show_caches is
True
, this function will display inline cache entries used by the interpreter to specialize the bytecode.If adaptive is
True
, this function will display specialized bytecode that may be different from the original bytecode.Changed in version 3.4: Added file parameter.
Changed in version 3.7: Implemented recursive disassembling and added depth parameter.
Changed in version 3.7: This can now handle coroutine and asynchronous generator objects.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter.
Changed in version 3.14: Added the show_positions parameter.
- dis.distb(tb=None, *, file=None, show_caches=False, adaptive=False, show_offset=False, show_positions=False)¶
Disassemble the top-of-stack function of a traceback, using the last traceback if none was passed. The instruction causing the exception is indicated.
The disassembly is written as text to the supplied file argument if provided and to
sys.stdout
otherwise.Changed in version 3.4: Added file parameter.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter.
Changed in version 3.14: Added the show_positions parameter.
- dis.disassemble(code, lasti=-1, *, file=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
- dis.disco(code, lasti=-1, *, file=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
Disassemble a code object, indicating the last instruction if lasti was provided. The output is divided in the following columns:
the source code location of the instruction. Complete location information is shown if show_positions is true. Otherwise (the default) only the line number is displayed.
the current instruction, indicated as
-->
,a labelled instruction, indicated with
>>
,the address of the instruction,
the operation code name,
operation parameters, and
interpretation of the parameters in parentheses.
The parameter interpretation recognizes local and global variable names, constant values, branch targets, and compare operators.
The disassembly is written as text to the supplied file argument if provided and to
sys.stdout
otherwise.Changed in version 3.4: Added file parameter.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter.
Changed in version 3.14: Added the show_positions parameter.
- dis.get_instructions(x, *, first_line=None, show_caches=False, adaptive=False)¶
Return an iterator over the instructions in the supplied function, method, source code string or code object.
The iterator generates a series of
Instruction
named tuples giving the details of each operation in the supplied code.If first_line is not
None
, it indicates the line number that should be reported for the first source line in the disassembled code. Otherwise, the source line information (if any) is taken directly from the disassembled code object.The adaptive parameter works as it does in
dis()
.Added in version 3.4.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: The show_caches parameter is deprecated and has no effect. The iterator generates the
Instruction
instances with the cache_info field populated (regardless of the value of show_caches) and it no longer generates separate items for the cache entries.
- dis.findlinestarts(code)¶
This generator function uses the
co_lines()
method of the code object code to find the offsets which are starts of lines in the source code. They are generated as(offset, lineno)
pairs.Changed in version 3.6: Line numbers can be decreasing. Before, they were always increasing.
Changed in version 3.10: The PEP 626
co_lines()
method is used instead of theco_firstlineno
andco_lnotab
attributes of the code object.Changed in version 3.13: Line numbers can be
None
for bytecode that does not map to source lines.
- dis.findlabels(code)¶
Detect all offsets in the raw compiled bytecode string code which are jump targets, and return a list of these offsets.
- dis.stack_effect(opcode, oparg=None, *, jump=None)¶
Compute the stack effect of opcode with argument oparg.
If the code has a jump target and jump is
True
,stack_effect()
will return the stack effect of jumping. If jump isFalse
, it will return the stack effect of not jumping. And if jump isNone
(default), it will return the maximal stack effect of both cases.Added in version 3.4.
Changed in version 3.8: Added jump parameter.
Changed in version 3.13: If
oparg
is omitted (orNone
), the stack effect is now returned foroparg=0
. Previously this was an error for opcodes that use their arg. It is also no longer an error to pass an integeroparg
when theopcode
does not use it; theoparg
in this case is ignored.
Python Bytecode Instructions¶
The get_instructions()
function and Bytecode
class provide
details of bytecode instructions as Instruction
instances:
- class dis.Instruction¶
Details for a bytecode operation
- opcode¶
numeric code for operation, corresponding to the opcode values listed below and the bytecode values in the Opcode collections.
- opname¶
human readable name for operation
- baseopcode¶
numeric code for the base operation if operation is specialized; otherwise equal to
opcode
- baseopname¶
human readable name for the base operation if operation is specialized; otherwise equal to
opname
- arg¶
numeric argument to operation (if any), otherwise
None
- argval¶
resolved arg value (if any), otherwise
None
- argrepr¶
human readable description of operation argument (if any), otherwise an empty string.
- offset¶
start index of operation within bytecode sequence
- start_offset¶
start index of operation within bytecode sequence, including prefixed
EXTENDED_ARG
operations if present; otherwise equal tooffset
- cache_offset¶
start index of the cache entries following the operation
- end_offset¶
end index of the cache entries following the operation
- starts_line¶
True
if this opcode starts a source line, otherwiseFalse
- line_number¶
source line number associated with this opcode (if any), otherwise
None
- is_jump_target¶
True
if other code jumps to here, otherwiseFalse
- jump_target¶
bytecode index of the jump target if this is a jump operation, otherwise
None
- positions¶
dis.Positions
object holding the start and end locations that are covered by this instruction.
- cache_info¶
Information about the cache entries of this instruction, as triplets of the form
(name, size, data)
, where thename
andsize
describe the cache format and data is the contents of the cache.cache_info
isNone
if the instruction does not have caches.
Added in version 3.4.
Changed in version 3.11: Field
positions
is added.Changed in version 3.13: Changed field
starts_line
.Added fields
start_offset
,cache_offset
,end_offset
,baseopname
,baseopcode
,jump_target
,oparg
,line_number
andcache_info
.
- class dis.Positions¶
In case the information is not available, some fields might be
None
.- lineno¶
- end_lineno¶
- col_offset¶
- end_col_offset¶
Added in version 3.11.
The Python compiler currently generates the following bytecode instructions.
General instructions
In the following, We will refer to the interpreter stack as STACK
and describe
operations on it as if it was a Python list. The top of the stack corresponds to
STACK[-1]
in this language.
- NOP¶
Do nothing code. Used as a placeholder by the bytecode optimizer, and to generate line tracing events.
- NOT_TAKEN¶
Do nothing code. Used by the interpreter to record
BRANCH_LEFT
andBRANCH_RIGHT
events forsys.monitoring
.Added in version 3.14.
- POP_ITER¶
Removes the iterator from the top of the stack.
Added in version 3.14.
- POP_TOP¶
Removes the top-of-stack item:
STACK.pop()
- END_FOR¶
Removes the top-of-stack item. Equivalent to
POP_TOP
. Used to clean up at the end of loops, hence the name.Added in version 3.12.
- END_SEND¶
Implements
del STACK[-2]
. Used to clean up when a generator exits.Added in version 3.12.
- COPY(i)¶
Push the i-th item to the top of the stack without removing it from its original location:
assert i > 0 STACK.append(STACK[-i])
Added in version 3.11.
- SWAP(i)¶
Swap the top of the stack with the i-th element:
STACK[-i], STACK[-1] = STACK[-1], STACK[-i]
Added in version 3.11.
- CACHE¶
Rather than being an actual instruction, this opcode is used to mark extra space for the interpreter to cache useful data directly in the bytecode itself. It is automatically hidden by all
dis
utilities, but can be viewed withshow_caches=True
.Logically, this space is part of the preceding instruction. Many opcodes expect to be followed by an exact number of caches, and will instruct the interpreter to skip over them at runtime.
Populated caches can look like arbitrary instructions, so great care should be taken when reading or modifying raw, adaptive bytecode containing quickened data.
Added in version 3.11.
Unary operations
Unary operations take the top of the stack, apply the operation, and push the result back on the stack.
- UNARY_NEGATIVE¶
Implements
STACK[-1] = -STACK[-1]
.
- UNARY_NOT¶
Implements
STACK[-1] = not STACK[-1]
.Changed in version 3.13: This instruction now requires an exact
bool
operand.
- UNARY_INVERT¶
Implements
STACK[-1] = ~STACK[-1]
.
- GET_ITER¶
Implements
STACK[-1] = iter(STACK[-1])
.
- GET_YIELD_FROM_ITER¶
If
STACK[-1]
is a generator iterator or coroutine object it is left as is. Otherwise, implementsSTACK[-1] = iter(STACK[-1])
.Added in version 3.5.
- TO_BOOL¶
Implements
STACK[-1] = bool(STACK[-1])
.Added in version 3.13.
Binary and in-place operations
Binary operations remove the top two items from the stack (STACK[-1]
and
STACK[-2]
). They perform the operation, then put the result back on the stack.
In-place operations are like binary operations, but the operation is done in-place
when STACK[-2]
supports it, and the resulting STACK[-1]
may be (but does
not have to be) the original STACK[-2]
.
- BINARY_OP(op)¶
Implements the binary and in-place operators (depending on the value of op):
rhs = STACK.pop() lhs = STACK.pop() STACK.append(lhs op rhs)
Added in version 3.11.
Changed in version 3.14: With oparg :
NB_SUBSCR
, implements binary subscript (replaces opcodeBINARY_SUBSCR
)
- STORE_SUBSCR¶
Implements:
key = STACK.pop() container = STACK.pop() value = STACK.pop() container[key] = value
- DELETE_SUBSCR¶
Implements:
key = STACK.pop() container = STACK.pop() del container[key]
- BINARY_SLICE¶
Implements:
end = STACK.pop() start = STACK.pop() container = STACK.pop() STACK.append(container[start:end])
Added in version 3.12.
- STORE_SLICE¶
Implements:
end = STACK.pop() start = STACK.pop() container = STACK.pop() value = STACK.pop() container[start:end] = value
Added in version 3.12.
Coroutine opcodes
- GET_AWAITABLE(where)¶
Implements
STACK[-1] = get_awaitable(STACK[-1])
, whereget_awaitable(o)
returnso
ifo
is a coroutine object or a generator object with theCO_ITERABLE_COROUTINE
flag, or resolveso.__await__
.If the
where
operand is nonzero, it indicates where the instruction occurs:1
: After a call to__aenter__
2
: After a call to__aexit__
Added in version 3.5.
Changed in version 3.11: Previously, this instruction did not have an oparg.
- GET_AITER¶
Implements
STACK[-1] = STACK[-1].__aiter__()
.Added in version 3.5.
Changed in version 3.7: Returning awaitable objects from
__aiter__
is no longer supported.
- GET_ANEXT¶
Implement
STACK.append(get_awaitable(STACK[-1].__anext__()))
to the stack. SeeGET_AWAITABLE
for details aboutget_awaitable
.Added in version 3.5.
- END_ASYNC_FOR¶
Terminates an
async for
loop. Handles an exception raised when awaiting a next item. The stack contains the async iterable inSTACK[-2]
and the raised exception inSTACK[-1]
. Both are popped. If the exception is notStopAsyncIteration
, it is re-raised.Added in version 3.8.
Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.
- CLEANUP_THROW¶
Handles an exception raised during a
throw()
orclose()
call through the current frame. IfSTACK[-1]
is an instance ofStopIteration
, pop three values from the stack and push itsvalue
member. Otherwise, re-raiseSTACK[-1]
.Added in version 3.12.
Miscellaneous opcodes
- SET_ADD(i)¶
Implements:
item = STACK.pop() set.add(STACK[-i], item)
Used to implement set comprehensions.
- LIST_APPEND(i)¶
Implements:
item = STACK.pop() list.append(STACK[-i], item)
Used to implement list comprehensions.
- MAP_ADD(i)¶
Implements:
value = STACK.pop() key = STACK.pop() dict.__setitem__(STACK[-i], key, value)
Used to implement dict comprehensions.
Added in version 3.1.
Changed in version 3.8: Map value is
STACK[-1]
and map key isSTACK[-2]
. Before, those were reversed.
For all of the SET_ADD
, LIST_APPEND
and MAP_ADD
instructions, while the added value or key/value pair is popped off, the
container object remains on the stack so that it is available for further
iterations of the loop.
- RETURN_VALUE¶
Returns with
STACK[-1]
to the caller of the function.
- YIELD_VALUE¶
Yields
STACK.pop()
from a generator.Changed in version 3.11: oparg set to be the stack depth.
Changed in version 3.12: oparg set to be the exception block depth, for efficient closing of generators.
Changed in version 3.13: oparg is
1
if this instruction is part of a yield-from or await, and0
otherwise.
- SETUP_ANNOTATIONS¶
Checks whether
__annotations__
is defined inlocals()
, if not it is set up to an emptydict
. This opcode is only emitted if a class or module body contains variable annotations statically.Added in version 3.6.
- POP_EXCEPT¶
Pops a value from the stack, which is used to restore the exception state.
Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.
- RERAISE¶
Re-raises the exception currently on top of the stack. If oparg is non-zero, pops an additional value from the stack which is used to set
f_lasti
of the current frame.Added in version 3.9.
Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.
- PUSH_EXC_INFO¶
Pops a value from the stack. Pushes the current exception to the top of the stack. Pushes the value originally popped back to the stack. Used in exception handlers.
Added in version 3.11.
- CHECK_EXC_MATCH¶
Performs exception matching for
except
. Tests whether theSTACK[-2]
is an exception matchingSTACK[-1]
. PopsSTACK[-1]
and pushes the boolean result of the test.Added in version 3.11.
- CHECK_EG_MATCH¶
Performs exception matching for
except*
. Appliessplit(STACK[-1])
on the exception group representingSTACK[-2]
.In case of a match, pops two items from the stack and pushes the non-matching subgroup (
None
in case of full match) followed by the matching subgroup. When there is no match, pops one item (the match type) and pushesNone
.Added in version 3.11.
- WITH_EXCEPT_START¶
Calls the function in position 4 on the stack with arguments (type, val, tb) representing the exception at the top of the stack. Used to implement the call
context_manager.__exit__(*exc_info())
when an exception has occurred in awith
statement.Added in version 3.9.
Changed in version 3.11: The
__exit__
function is in position 4 of the stack rather than 7. Exception representation on the stack now consist of one, not three, items.
- LOAD_COMMON_CONSTANT¶
Pushes a common constant onto the stack. The interpreter contains a hardcoded list of constants supported by this instruction. Used by the
assert
statement to loadAssertionError
.Added in version 3.14.
- LOAD_BUILD_CLASS¶
Pushes
builtins.__build_class__()
onto the stack. It is later called to construct a class.
- GET_LEN¶
Perform
STACK.append(len(STACK[-1]))
. Used inmatch
statements where comparison with structure of pattern is needed.Added in version 3.10.
- MATCH_MAPPING¶
If
STACK[-1]
is an instance ofcollections.abc.Mapping
(or, more technically: if it has thePy_TPFLAGS_MAPPING
flag set in itstp_flags
), pushTrue
onto the stack. Otherwise, pushFalse
.Added in version 3.10.
- MATCH_SEQUENCE¶
If
STACK[-1]
is an instance ofcollections.abc.Sequence
and is not an instance ofstr
/bytes
/bytearray
(or, more technically: if it has thePy_TPFLAGS_SEQUENCE
flag set in itstp_flags
), pushTrue
onto the stack. Otherwise, pushFalse
.Added in version 3.10.
- MATCH_KEYS¶
STACK[-1]
is a tuple of mapping keys, andSTACK[-2]
is the match subject. IfSTACK[-2]
contains all of the keys inSTACK[-1]
, push atuple
containing the corresponding values. Otherwise, pushNone
.Added in version 3.10.
Changed in version 3.11: Previously, this instruction also pushed a boolean value indicating success (
True
) or failure (False
).
- STORE_NAME(namei)¶
Implements
name = STACK.pop()
. namei is the index of name in the attributeco_names
of the code object. The compiler tries to useSTORE_FAST
orSTORE_GLOBAL
if possible.
- DELETE_NAME(namei)¶
Implements
del name
, where namei is the index intoco_names
attribute of the code object.
- UNPACK_SEQUENCE(count)¶
Unpacks
STACK[-1]
into count individual values, which are put onto the stack right-to-left. Require there to be exactly count values.:assert(len(STACK[-1]) == count) STACK.extend(STACK.pop()[:-count-1:-1])
- UNPACK_EX(counts)¶
Implements assignment with a starred target: Unpacks an iterable in
STACK[-1]
into individual values, where the total number of values can be smaller than the number of items in the iterable: one of the new values will be a list of all leftover items.The number of values before and after the list value is limited to 255.
The number of values before the list value is encoded in the argument of the opcode. The number of values after the list if any is encoded using an
EXTENDED_ARG
. As a consequence, the argument can be seen as a two bytes values where the low byte of counts is the number of values before the list value, the high byte of counts the number of values after it.The extracted values are put onto the stack right-to-left, i.e.
a, *b, c = d
will be stored after execution asSTACK.extend((a, b, c))
.
- STORE_ATTR(namei)¶
Implements:
obj = STACK.pop() value = STACK.pop() obj.name = value
where namei is the index of name in
co_names
of the code object.
- DELETE_ATTR(namei)¶
Implements:
obj = STACK.pop() del obj.name
where namei is the index of name into
co_names
of the code object.
- STORE_GLOBAL(namei)¶
Works as
STORE_NAME
, but stores the name as a global.
- DELETE_GLOBAL(namei)¶
Works as
DELETE_NAME
, but deletes a global name.
- LOAD_CONST(consti)¶
Pushes
co_consts[consti]
onto the stack.
- LOAD_SMALL_INT(i)¶
Pushes the integer
i
onto the stack.i
must be inrange(256)
Added in version 3.14.
- LOAD_NAME(namei)¶
Pushes the value associated with
co_names[namei]
onto the stack. The name is looked up within the locals, then the globals, then the builtins.
- LOAD_LOCALS¶
Pushes a reference to the locals dictionary onto the stack. This is used to prepare namespace dictionaries for
LOAD_FROM_DICT_OR_DEREF
andLOAD_FROM_DICT_OR_GLOBALS
.Added in version 3.12.
- LOAD_FROM_DICT_OR_GLOBALS(i)¶
Pops a mapping off the stack and looks up the value for
co_names[namei]
. If the name is not found there, looks it up in the globals and then the builtins, similar toLOAD_GLOBAL
. This is used for loading global variables in annotation scopes within class bodies.Added in version 3.12.
- BUILD_TEMPLATE¶
Constructs a new
Template
instance from a tuple of strings and a tuple of interpolations and pushes the resulting object onto the stack:interpolations = STACK.pop() strings = STACK.pop() STACK.append(_build_template(strings, interpolations))
Added in version 3.14.
- BUILD_INTERPOLATION(format)¶
Constructs a new
Interpolation
instance from a value and its source expression and pushes the resulting object onto the stack.If no conversion or format specification is present,
format
is set to2
.If the low bit of
format
is set, it indicates that the interpolation contains a format specification.If
format >> 2
is non-zero, it indicates that the interpolation contains a conversion. The value offormat >> 2
is the conversion type (0
for no conversion,1
for!s
,2
for!r
, and3
for!a
):conversion = format >> 2 if format & 1: format_spec = STACK.pop() else: format_spec = None expression = STACK.pop() value = STACK.pop() STACK.append(_build_interpolation(value, expression, conversion, format_spec))
Added in version 3.14.
- BUILD_TUPLE(count)¶
Creates a tuple consuming count items from the stack, and pushes the resulting tuple onto the stack:
if count == 0: value = () else: value = tuple(STACK[-count:]) STACK = STACK[:-count] STACK.append(value)
- BUILD_LIST(count)¶
Works as
BUILD_TUPLE
, but creates a list.
- BUILD_SET(count)¶
Works as
BUILD_TUPLE
, but creates a set.
- BUILD_MAP(count)¶
Pushes a new dictionary object onto the stack. Pops
2 * count
items so that the dictionary holds count entries:{..., STACK[-4]: STACK[-3], STACK[-2]: STACK[-1]}
.Changed in version 3.5: The dictionary is created from stack items instead of creating an empty dictionary pre-sized to hold count items.
- BUILD_STRING(count)¶
Concatenates count strings from the stack and pushes the resulting string onto the stack.
Added in version 3.6.
- LIST_EXTEND(i)¶
Implements:
seq = STACK.pop() list.extend(STACK[-i], seq)
Used to build lists.
Added in version 3.9.
- SET_UPDATE(i)¶
Implements:
seq = STACK.pop() set.update(STACK[-i], seq)
Used to build sets.
Added in version 3.9.
- DICT_UPDATE(i)¶
Implements:
map = STACK.pop() dict.update(STACK[-i], map)
Used to build dicts.
Added in version 3.9.
- DICT_MERGE(i)¶
Like
DICT_UPDATE
but raises an exception for duplicate keys.Added in version 3.9.
- LOAD_ATTR(namei)¶
If the low bit of
namei
is not set, this replacesSTACK[-1]
withgetattr(STACK[-1], co_names[namei>>1])
.If the low bit of
namei
is set, this will attempt to load a method namedco_names[namei>>1]
from theSTACK[-1]
object.STACK[-1]
is popped. This bytecode distinguishes two cases: ifSTACK[-1]
has a method with the correct name, the bytecode pushes the unbound method andSTACK[-1]
.STACK[-1]
will be used as the first argument (self
) byCALL
orCALL_KW
when calling the unbound method. Otherwise,NULL
and the object returned by the attribute lookup are pushed.Changed in version 3.12: If the low bit of
namei
is set, then aNULL
orself
is pushed to the stack before the attribute or unbound method respectively.
- LOAD_SUPER_ATTR(namei)¶
This opcode implements
super()
, both in its zero-argument and two-argument forms (e.g.super().method()
,super().attr
andsuper(cls, self).method()
,super(cls, self).attr
).It pops three values from the stack (from top of stack down):
self
: the first argument to the current methodcls
: the class within which the current method was definedthe global
super
With respect to its argument, it works similarly to
LOAD_ATTR
, except thatnamei
is shifted left by 2 bits instead of 1.The low bit of
namei
signals to attempt a method load, as withLOAD_ATTR
, which results in pushingNULL
and the loaded method. When it is unset a single value is pushed to the stack.The second-low bit of
namei
, if set, means that this was a two-argument call tosuper()
(unset means zero-argument).Added in version 3.12.
- COMPARE_OP(opname)¶
Performs a Boolean operation. The operation name can be found in
cmp_op[opname >> 5]
. If the fifth-lowest bit ofopname
is set (opname & 16
), the result should be coerced tobool
.Changed in version 3.13: The fifth-lowest bit of the oparg now indicates a forced conversion to
bool
.
- IS_OP(invert)¶
Performs
is
comparison, oris not
ifinvert
is 1.Added in version 3.9.
- CONTAINS_OP(invert)¶
Performs
in
comparison, ornot in
ifinvert
is 1.Added in version 3.9.
- IMPORT_NAME(namei)¶
Imports the module
co_names[namei]
.STACK[-1]
andSTACK[-2]
are popped and provide the fromlist and level arguments of__import__()
. The module object is pushed onto the stack. The current namespace is not affected: for a proper import statement, a subsequentSTORE_FAST
instruction modifies the namespace.
- IMPORT_FROM(namei)¶
Loads the attribute
co_names[namei]
from the module found inSTACK[-1]
. The resulting object is pushed onto the stack, to be subsequently stored by aSTORE_FAST
instruction.
- JUMP_FORWARD(delta)¶
Increments bytecode counter by delta.
- JUMP_BACKWARD(delta)¶
Decrements bytecode counter by delta. Checks for interrupts.
Added in version 3.11.
- JUMP_BACKWARD_NO_INTERRUPT(delta)¶
Decrements bytecode counter by delta. Does not check for interrupts.
Added in version 3.11.
- POP_JUMP_IF_TRUE(delta)¶
If
STACK[-1]
is true, increments the bytecode counter by delta.STACK[-1]
is popped.Changed in version 3.11: The oparg is now a relative delta rather than an absolute target. This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).
Changed in version 3.12: This is no longer a pseudo-instruction.
Changed in version 3.13: This instruction now requires an exact
bool
operand.
- POP_JUMP_IF_FALSE(delta)¶
If
STACK[-1]
is false, increments the bytecode counter by delta.STACK[-1]
is popped.Changed in version 3.11: The oparg is now a relative delta rather than an absolute target. This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).
Changed in version 3.12: This is no longer a pseudo-instruction.
Changed in version 3.13: This instruction now requires an exact
bool
operand.
- POP_JUMP_IF_NOT_NONE(delta)¶
If
STACK[-1]
is notNone
, increments the bytecode counter by delta.STACK[-1]
is popped.Added in version 3.11.
Changed in version 3.12: This is no longer a pseudo-instruction.
- POP_JUMP_IF_NONE(delta)¶
If
STACK[-1]
isNone
, increments the bytecode counter by delta.STACK[-1]
is popped.Added in version 3.11.
Changed in version 3.12: This is no longer a pseudo-instruction.
- FOR_ITER(delta)¶
STACK[-1]
is an iterator. Call its__next__()
method. If this yields a new value, push it on the stack (leaving the iterator below it). If the iterator indicates it is exhausted then the byte code counter is incremented by delta.Changed in version 3.12: Up until 3.11 the iterator was popped when it was exhausted.
- LOAD_GLOBAL(namei)¶
Loads the global named
co_names[namei>>1]
onto the stack.Changed in version 3.11: If the low bit of
namei
is set, then aNULL
is pushed to the stack before the global variable.
- LOAD_FAST(var_num)¶
Pushes a reference to the local
co_varnames[var_num]
onto the stack.Changed in version 3.12: This opcode is now only used in situations where the local variable is guaranteed to be initialized. It cannot raise
UnboundLocalError
.
- LOAD_FAST_BORROW(var_num)¶
Pushes a borrowed reference to the local
co_varnames[var_num]
onto the stack.Added in version 3.14.
- LOAD_FAST_LOAD_FAST(var_nums)¶
Pushes references to
co_varnames[var_nums >> 4]
andco_varnames[var_nums & 15]
onto the stack.Added in version 3.13.
- LOAD_FAST_BORROW_LOAD_FAST_BORROW(var_nums)¶
Pushes borrowed references to
co_varnames[var_nums >> 4]
andco_varnames[var_nums & 15]
onto the stack.Added in version 3.14.
- LOAD_FAST_CHECK(var_num)¶
Pushes a reference to the local
co_varnames[var_num]
onto the stack, raising anUnboundLocalError
if the local variable has not been initialized.Added in version 3.12.
- LOAD_FAST_AND_CLEAR(var_num)¶
Pushes a reference to the local
co_varnames[var_num]
onto the stack (or pushesNULL
onto the stack if the local variable has not been initialized) and setsco_varnames[var_num]
toNULL
.Added in version 3.12.
- STORE_FAST(var_num)¶
Stores
STACK.pop()
into the localco_varnames[var_num]
.
- STORE_FAST_STORE_FAST(var_nums)¶
Stores
STACK[-1]
intoco_varnames[var_nums >> 4]
andSTACK[-2]
intoco_varnames[var_nums & 15]
.Added in version 3.13.
- STORE_FAST_LOAD_FAST(var_nums)¶
Stores
STACK.pop()
into the localco_varnames[var_nums >> 4]
and pushes a reference to the localco_varnames[var_nums & 15]
onto the stack.Added in version 3.13.
- DELETE_FAST(var_num)¶
Deletes local
co_varnames[var_num]
.
- MAKE_CELL(i)¶
Creates a new cell in slot
i
. If that slot is nonempty then that value is stored into the new cell.Added in version 3.11.
- LOAD_DEREF(i)¶
Loads the cell contained in slot
i
of the “fast locals” storage. Pushes a reference to the object the cell contains on the stack.Changed in version 3.11:
i
is no longer offset by the length ofco_varnames
.
- LOAD_FROM_DICT_OR_DEREF(i)¶
Pops a mapping off the stack and looks up the name associated with slot
i
of the “fast locals” storage in this mapping. If the name is not found there, loads it from the cell contained in sloti
, similar toLOAD_DEREF
. This is used for loading closure variables in class bodies (which previously usedLOAD_CLASSDEREF
) and in annotation scopes within class bodies.Added in version 3.12.
- STORE_DEREF(i)¶
Stores
STACK.pop()
into the cell contained in sloti
of the “fast locals” storage.Changed in version 3.11:
i
is no longer offset by the length ofco_varnames
.
- DELETE_DEREF(i)¶
Empties the cell contained in slot
i
of the “fast locals” storage. Used by thedel
statement.Added in version 3.2.
Changed in version 3.11:
i
is no longer offset by the length ofco_varnames
.
- COPY_FREE_VARS(n)¶
Copies the
n
free (closure) variables from the closure into the frame. Removes the need for special code on the caller’s side when calling closures.Added in version 3.11.
- RAISE_VARARGS(argc)¶
Raises an exception using one of the 3 forms of the
raise
statement, depending on the value of argc:0:
raise
(re-raise previous exception)1:
raise STACK[-1]
(raise exception instance or type atSTACK[-1]
)2:
raise STACK[-2] from STACK[-1]
(raise exception instance or type atSTACK[-2]
with__cause__
set toSTACK[-1]
)
- CALL(argc)¶
Calls a callable object with the number of arguments specified by
argc
. On the stack are (in ascending order):The callable
self
orNULL
The remaining positional arguments
argc
is the total of the positional arguments, excludingself
.CALL
pops all arguments and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.Added in version 3.11.
Changed in version 3.13: The callable now always appears at the same position on the stack.
Changed in version 3.13: Calls with keyword arguments are now handled by
CALL_KW
.
- CALL_KW(argc)¶
Calls a callable object with the number of arguments specified by
argc
, including one or more named arguments. On the stack are (in ascending order):The callable
self
orNULL
The remaining positional arguments
The named arguments
A
tuple
of keyword argument names
argc
is the total of the positional and named arguments, excludingself
. The length of the tuple of keyword argument names is the number of named arguments.CALL_KW
pops all arguments, the keyword names, and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.Added in version 3.13.
- CALL_FUNCTION_EX(flags)¶
Calls a callable object with variable set of positional and keyword arguments. If the lowest bit of flags is set, the top of the stack contains a mapping object containing additional keyword arguments. Before the callable is called, the mapping object and iterable object are each “unpacked” and their contents passed in as keyword and positional arguments respectively.
CALL_FUNCTION_EX
pops all arguments and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.Added in version 3.6.
- PUSH_NULL¶
Pushes a
NULL
to the stack. Used in the call sequence to match theNULL
pushed byLOAD_METHOD
for non-method calls.Added in version 3.11.
- MAKE_FUNCTION¶
Pushes a new function object on the stack built from the code object at
STACK[-1]
.Changed in version 3.10: Flag value
0x04
is a tuple of strings instead of dictionaryChanged in version 3.11: Qualified name at
STACK[-1]
was removed.Changed in version 3.13: Extra function attributes on the stack, signaled by oparg flags, were removed. They now use
SET_FUNCTION_ATTRIBUTE
.
- SET_FUNCTION_ATTRIBUTE(flag)¶
Sets an attribute on a function object. Expects the function at
STACK[-1]
and the attribute value to set atSTACK[-2]
; consumes both and leaves the function atSTACK[-1]
. The flag determines which attribute to set:0x01
a tuple of default values for positional-only and positional-or-keyword parameters in positional order0x02
a dictionary of keyword-only parameters’ default values0x04
a tuple of strings containing parameters’ annotations0x08
a tuple containing cells for free variables, making a closure0x10
the annotate function for the function object
Added in version 3.13.
Changed in version 3.14: Added
0x10
to indicate the annotate function for the function object.
- BUILD_SLICE(argc)¶
Pushes a slice object on the stack. argc must be 2 or 3. If it is 2, implements:
end = STACK.pop() start = STACK.pop() STACK.append(slice(start, end))
if it is 3, implements:
step = STACK.pop() end = STACK.pop() start = STACK.pop() STACK.append(slice(start, end, step))
See the
slice()
built-in function for more information.
- EXTENDED_ARG(ext)¶
Prefixes any opcode which has an argument too big to fit into the default one byte. ext holds an additional byte which act as higher bits in the argument. For each opcode, at most three prefixal
EXTENDED_ARG
are allowed, forming an argument from two-byte to four-byte.
- CONVERT_VALUE(oparg)¶
Convert value to a string, depending on
oparg
:value = STACK.pop() result = func(value) STACK.append(result)
Used for implementing formatted string literals (f-strings).
Added in version 3.13.
- FORMAT_SIMPLE¶
Formats the value on top of stack:
value = STACK.pop() result = value.__format__("") STACK.append(result)
Used for implementing formatted string literals (f-strings).
Added in version 3.13.
- FORMAT_WITH_SPEC¶
Formats the given value with the given format spec:
spec = STACK.pop() value = STACK.pop() result = value.__format__(spec) STACK.append(result)
Used for implementing formatted string literals (f-strings).
Added in version 3.13.
- MATCH_CLASS(count)¶
STACK[-1]
is a tuple of keyword attribute names,STACK[-2]
is the class being matched against, andSTACK[-3]
is the match subject. count is the number of positional sub-patterns.Pop
STACK[-1]
,STACK[-2]
, andSTACK[-3]
. IfSTACK[-3]
is an instance ofSTACK[-2]
and has the positional and keyword attributes required by count andSTACK[-1]
, push a tuple of extracted attributes. Otherwise, pushNone
.Added in version 3.10.
Changed in version 3.11: Previously, this instruction also pushed a boolean value indicating success (
True
) or failure (False
).
- RESUME(context)¶
A no-op. Performs internal tracing, debugging and optimization checks.
The
context
operand consists of two parts. The lowest two bits indicate where theRESUME
occurs:0
The start of a function, which is neither a generator, coroutine nor an async generator1
After ayield
expression2
After ayield from
expression3
After anawait
expression
The next bit is
1
if the RESUME is at except-depth1
, and0
otherwise.Added in version 3.11.
Changed in version 3.13: The oparg value changed to include information about except-depth
- RETURN_GENERATOR¶
Create a generator, coroutine, or async generator from the current frame. Used as first opcode of in code object for the above mentioned callables. Clear the current frame and return the newly created generator.
Added in version 3.11.
- SEND(delta)¶
Equivalent to
STACK[-1] = STACK[-2].send(STACK[-1])
. Used inyield from
andawait
statements.If the call raises
StopIteration
, pop the top value from the stack, push the exception’svalue
attribute, and increment the bytecode counter by delta.Added in version 3.11.
- HAVE_ARGUMENT¶
This is not really an opcode. It identifies the dividing line between opcodes in the range [0,255] which don’t use their argument and those that do (
< HAVE_ARGUMENT
and>= HAVE_ARGUMENT
, respectively).If your application uses pseudo instructions or specialized instructions, use the
hasarg
collection instead.Changed in version 3.6: Now every instruction has an argument, but opcodes
< HAVE_ARGUMENT
ignore it. Before, only opcodes>= HAVE_ARGUMENT
had an argument.Changed in version 3.12: Pseudo instructions were added to the
dis
module, and for them it is not true that comparison withHAVE_ARGUMENT
indicates whether they use their arg.Deprecated since version 3.13: Use
hasarg
instead.
- CALL_INTRINSIC_1¶
Calls an intrinsic function with one argument. Passes
STACK[-1]
as the argument and setsSTACK[-1]
to the result. Used to implement functionality that is not performance critical.The operand determines which intrinsic function is called:
Operand
Description
INTRINSIC_1_INVALID
Not valid
INTRINSIC_PRINT
Prints the argument to standard out. Used in the REPL.
INTRINSIC_IMPORT_STAR
Performs
import *
for the named module.INTRINSIC_STOPITERATION_ERROR
Extracts the return value from a
StopIteration
exception.INTRINSIC_ASYNC_GEN_WRAP
Wraps an async generator value
INTRINSIC_UNARY_POSITIVE
Performs the unary
+
operationINTRINSIC_LIST_TO_TUPLE
Converts a list to a tuple
INTRINSIC_TYPEVAR
Creates a
typing.TypeVar
INTRINSIC_PARAMSPEC
Creates a
typing.ParamSpec
INTRINSIC_TYPEVARTUPLE
Creates a
typing.TypeVarTuple
INTRINSIC_SUBSCRIPT_GENERIC
Returns
typing.Generic
subscripted with the argumentINTRINSIC_TYPEALIAS
Creates a
typing.TypeAliasType
; used in thetype
statement. The argument is a tuple of the type alias’s name, type parameters, and value.Added in version 3.12.
- CALL_INTRINSIC_2¶
Calls an intrinsic function with two arguments. Used to implement functionality that is not performance critical:
arg2 = STACK.pop() arg1 = STACK.pop() result = intrinsic2(arg1, arg2) STACK.append(result)
The operand determines which intrinsic function is called:
Operand
Description
INTRINSIC_2_INVALID
Not valid
INTRINSIC_PREP_RERAISE_STAR
Calculates the
ExceptionGroup
to raise from atry-except*
.INTRINSIC_TYPEVAR_WITH_BOUND
Creates a
typing.TypeVar
with a bound.INTRINSIC_TYPEVAR_WITH_CONSTRAINTS
Creates a
typing.TypeVar
with constraints.INTRINSIC_SET_FUNCTION_TYPE_PARAMS
Sets the
__type_params__
attribute of a function.Added in version 3.12.
- LOAD_SPECIAL¶
Performs special method lookup on
STACK[-1]
. Iftype(STACK[-1]).__xxx__
is a method, leavetype(STACK[-1]).__xxx__; STACK[-1]
on the stack. Iftype(STACK[-1]).__xxx__
is not a method, leaveSTACK[-1].__xxx__; NULL
on the stack.Added in version 3.14.
Pseudo-instructions
These opcodes do not appear in Python bytecode. They are used by the compiler but are replaced by real opcodes or removed before bytecode is generated.
- SETUP_FINALLY(target)¶
Set up an exception handler for the following code block. If an exception occurs, the value stack level is restored to its current state and control is transferred to the exception handler at
target
.
- SETUP_CLEANUP(target)¶
Like
SETUP_FINALLY
, but in case of an exception also pushes the last instruction (lasti
) to the stack so thatRERAISE
can restore it. If an exception occurs, the value stack level and the last instruction on the frame are restored to their current state, and control is transferred to the exception handler attarget
.
- SETUP_WITH(target)¶
Like
SETUP_CLEANUP
, but in case of an exception one more item is popped from the stack before control is transferred to the exception handler attarget
.This variant is used in
with
andasync with
constructs, which push the return value of the context manager’s__enter__()
or__aenter__()
to the stack.
- POP_BLOCK¶
Marks the end of the code block associated with the last
SETUP_FINALLY
,SETUP_CLEANUP
orSETUP_WITH
.
- LOAD_CONST_IMMORTAL(consti)¶
Works as
LOAD_CONST
, but is more efficient for immortal objects.
- JUMP¶
- JUMP_NO_INTERRUPT¶
Undirected relative jump instructions which are replaced by their directed (forward/backward) counterparts by the assembler.
- JUMP_IF_TRUE¶
- JUMP_IF_FALSE¶
Conditional jumps which do not impact the stack. Replaced by the sequence
COPY 1
,TO_BOOL
,POP_JUMP_IF_TRUE/FALSE
.
- LOAD_CLOSURE(i)¶
Pushes a reference to the cell contained in slot
i
of the “fast locals” storage.Note that
LOAD_CLOSURE
is replaced withLOAD_FAST
in the assembler.Changed in version 3.13: This opcode is now a pseudo-instruction.
Opcode collections¶
These collections are provided for automatic introspection of bytecode instructions:
Changed in version 3.12: The collections now contain pseudo instructions and instrumented
instructions as well. These are opcodes with values >= MIN_PSEUDO_OPCODE
and >= MIN_INSTRUMENTED_OPCODE
.
- dis.opname¶
Sequence of operation names, indexable using the bytecode.
- dis.opmap¶
Dictionary mapping operation names to bytecodes.
- dis.cmp_op¶
Sequence of all compare operation names.
- dis.hasarg¶
Sequence of bytecodes that use their argument.
Added in version 3.12.
- dis.hasconst¶
Sequence of bytecodes that access a constant.
- dis.hasfree¶
Sequence of bytecodes that access a free (closure) variable. ‘free’ in this context refers to names in the current scope that are referenced by inner scopes or names in outer scopes that are referenced from this scope. It does not include references to global or builtin scopes.
- dis.hasname¶
Sequence of bytecodes that access an attribute by name.
- dis.hasjump¶
Sequence of bytecodes that have a jump target. All jumps are relative.
Added in version 3.13.
- dis.haslocal¶
Sequence of bytecodes that access a local variable.
- dis.hascompare¶
Sequence of bytecodes of Boolean operations.
- dis.hasexc¶
Sequence of bytecodes that set an exception handler.
Added in version 3.12.
- dis.hasjrel¶
Sequence of bytecodes that have a relative jump target.
Deprecated since version 3.13: All jumps are now relative. Use
hasjump
.
- dis.hasjabs¶
Sequence of bytecodes that have an absolute jump target.
Deprecated since version 3.13: All jumps are now relative. This list is empty.