Unicode Objects and Codecs

Unicode Objects and Codecs¶
Unicode Objects¶
Since the implementation of PEP 393 in Python 3.3, Unicode objects internally use a variety of representations, in order to allow handling the complete range of Unicode characters while staying memory efficient. There are special cases for strings where all code points are below 128, 256, or 65536; otherwise, code points must be below 1114112 (which is the full Unicode range).
UTF-8 representation is created on demand and cached in the Unicode object.
Note
The Py_UNICODE
representation has been removed since Python 3.12
with deprecated APIs.
See PEP 623 for more information.
Unicode Type¶
These are the basic Unicode object types used for the Unicode implementation in Python:
-
PyTypeObject PyUnicode_Type¶
- Part of the Stable ABI.
This instance of
PyTypeObject
represents the Python Unicode type. It is exposed to Python code asstr
.
-
PyTypeObject PyUnicodeIter_Type¶
- Part of the Stable ABI.
This instance of
PyTypeObject
represents the Python Unicode iterator type. It is used to iterate over Unicode string objects.
-
type Py_UCS4¶
-
type Py_UCS2¶
-
type Py_UCS1¶
- Part of the Stable ABI.
These types are typedefs for unsigned integer types wide enough to contain characters of 32 bits, 16 bits and 8 bits, respectively. When dealing with single Unicode characters, use
Py_UCS4
.Added in version 3.3.
-
type PyASCIIObject¶
-
type PyCompactUnicodeObject¶
-
type PyUnicodeObject¶
These subtypes of
PyObject
represent a Python Unicode object. In almost all cases, they shouldn’t be used directly, since all API functions that deal with Unicode objects take and returnPyObject
pointers.Added in version 3.3.
The structure of a particular object can be determined using the following macros. The macros cannot fail; their behavior is undefined if their argument is not a Python Unicode object.
-
PyUnicode_IS_COMPACT(o)¶
True if o uses the
PyCompactUnicodeObject
structure.Added in version 3.3.
-
PyUnicode_IS_COMPACT_ASCII(o)¶
True if o uses the
PyASCIIObject
structure.Added in version 3.3.
-
PyUnicode_IS_COMPACT(o)¶
The following APIs are C macros and static inlined functions for fast checks and access to internal read-only data of Unicode objects:
-
int PyUnicode_Check(PyObject *obj)¶
Return true if the object obj is a Unicode object or an instance of a Unicode subtype. This function always succeeds.
-
int PyUnicode_CheckExact(PyObject *obj)¶
Return true if the object obj is a Unicode object, but not an instance of a subtype. This function always succeeds.
-
Py_ssize_t PyUnicode_GET_LENGTH(PyObject *unicode)¶
Return the length of the Unicode string, in code points. unicode has to be a Unicode object in the “canonical” representation (not checked).
Added in version 3.3.
-
Py_UCS1 *PyUnicode_1BYTE_DATA(PyObject *unicode)¶
-
Py_UCS2 *PyUnicode_2BYTE_DATA(PyObject *unicode)¶
-
Py_UCS4 *PyUnicode_4BYTE_DATA(PyObject *unicode)¶
Return a pointer to the canonical representation cast to UCS1, UCS2 or UCS4 integer types for direct character access. No checks are performed if the canonical representation has the correct character size; use
PyUnicode_KIND()
to select the right function.Added in version 3.3.
-
PyUnicode_1BYTE_KIND¶
-
PyUnicode_2BYTE_KIND¶
-
PyUnicode_4BYTE_KIND¶
Return values of the
PyUnicode_KIND()
macro.Added in version 3.3.
Changed in version 3.12:
PyUnicode_WCHAR_KIND
has been removed.
-
int PyUnicode_KIND(PyObject *unicode)¶
Return one of the PyUnicode kind constants (see above) that indicate how many bytes per character this Unicode object uses to store its data. unicode has to be a Unicode object in the “canonical” representation (not checked).
Added in version 3.3.
-
void *PyUnicode_DATA(PyObject *unicode)¶
Return a void pointer to the raw Unicode buffer. unicode has to be a Unicode object in the “canonical” representation (not checked).
Added in version 3.3.
-
void PyUnicode_WRITE(int kind, void *data, Py_ssize_t index, Py_UCS4 value)¶
Write the code point value to the given zero-based index in a string.
The kind value and data pointer must have been obtained from a string using
PyUnicode_KIND()
andPyUnicode_DATA()
respectively. You must hold a reference to that string while callingPyUnicode_WRITE()
. All requirements ofPyUnicode_WriteChar()
also apply.The function performs no checks for any of its requirements, and is intended for usage in loops.
Added in version 3.3.
-
Py_UCS4 PyUnicode_READ(int kind, void *data, Py_ssize_t index)¶
Read a code point from a canonical representation data (as obtained with
PyUnicode_DATA()
). No checks or ready calls are performed.Added in version 3.3.
-
Py_UCS4 PyUnicode_READ_CHAR(PyObject *unicode, Py_ssize_t index)¶
Read a character from a Unicode object unicode, which must be in the “canonical” representation. This is less efficient than
PyUnicode_READ()
if you do multiple consecutive reads.Added in version 3.3.
-
Py_UCS4 PyUnicode_MAX_CHAR_VALUE(PyObject *unicode)¶
Return the maximum code point that is suitable for creating another string based on unicode, which must be in the “canonical” representation. This is always an approximation but more efficient than iterating over the string.
Added in version 3.3.
-
int PyUnicode_IsIdentifier(PyObject *unicode)¶
- Part of the Stable ABI.
Return
1
if the string is a valid identifier according to the language definition, section Names (identifiers and keywords). Return0
otherwise.Changed in version 3.9: The function does not call
Py_FatalError()
anymore if the string is not ready.
-
unsigned int PyUnicode_IS_ASCII(PyObject *unicode)¶
Return true if the string only contains ASCII characters. Equivalent to
str.isascii()
.Added in version 3.2.
Unicode Character Properties¶
Unicode provides many different character properties. The most often needed ones are available through these macros which are mapped to C functions depending on the Python configuration.
-
int Py_UNICODE_ISSPACE(Py_UCS4 ch)¶
Return
1
or0
depending on whether ch is a whitespace character.
-
int Py_UNICODE_ISUPPER(Py_UCS4 ch)¶
Return
1
or0
depending on whether ch is an uppercase character.
-
int Py_UNICODE_ISLINEBREAK(Py_UCS4 ch)¶
Return
1
or0
depending on whether ch is a linebreak character.
-
int Py_UNICODE_ISALPHA(Py_UCS4 ch)¶
Return
1
or0
depending on whether ch is an alphabetic character.
-
int Py_UNICODE_ISALNUM(Py_UCS4 ch)¶
Return
1
or0
depending on whether ch is an alphanumeric character.
-
int Py_UNICODE_ISPRINTABLE(Py_UCS4 ch)¶
Return
1
or0
depending on whether ch is a printable character, in the sense ofstr.isprintable()
.
These APIs can be used for fast direct character conversions:
-
int Py_UNICODE_TODECIMAL(Py_UCS4 ch)¶
Return the character ch converted to a decimal positive integer. Return
-1
if this is not possible. This function does not raise exceptions.
-
int Py_UNICODE_TODIGIT(Py_UCS4 ch)¶
Return the character ch converted to a single digit integer. Return
-1
if this is not possible. This function does not raise exceptions.
-
double Py_UNICODE_TONUMERIC(Py_UCS4 ch)¶
Return the character ch converted to a double. Return
-1.0
if this is not possible. This function does not raise exceptions.
These APIs can be used to work with surrogates:
-
int Py_UNICODE_IS_HIGH_SURROGATE(Py_UCS4 ch)¶
Check if ch is a high surrogate (
0xD800 <= ch <= 0xDBFF
).
-
int Py_UNICODE_IS_LOW_SURROGATE(Py_UCS4 ch)¶
Check if ch is a low surrogate (
0xDC00 <= ch <= 0xDFFF
).
-
Py_UCS4 Py_UNICODE_HIGH_SURROGATE(Py_UCS4 ch)¶
Return the high UTF-16 surrogate (
0xD800
to0xDBFF
) for a Unicode code point in the range[0x10000; 0x10FFFF]
.
-
Py_UCS4 Py_UNICODE_LOW_SURROGATE(Py_UCS4 ch)¶
Return the low UTF-16 surrogate (
0xDC00
to0xDFFF
) for a Unicode code point in the range[0x10000; 0x10FFFF]
.
-
Py_UCS4 Py_UNICODE_JOIN_SURROGATES(Py_UCS4 high, Py_UCS4 low)¶
Join two surrogate code points and return a single
Py_UCS4
value. high and low are respectively the leading and trailing surrogates in a surrogate pair. high must be in the range[0xD800; 0xDBFF]
and low must be in the range[0xDC00; 0xDFFF]
.
Creating and accessing Unicode strings¶
To create Unicode objects and access their basic sequence properties, use these APIs:
-
PyObject *PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)¶
- Return value: New reference.
Create a new Unicode object. maxchar should be the true maximum code point to be placed in the string. As an approximation, it can be rounded up to the nearest value in the sequence 127, 255, 65535, 1114111.
On error, set an exception and return
NULL
.After creation, the string can be filled by
PyUnicode_WriteChar()
,PyUnicode_CopyCharacters()
,PyUnicode_Fill()
,PyUnicode_WRITE()
or similar. Since strings are supposed to be immutable, take care to not “use” the result while it is being modified. In particular, before it’s filled with its final contents, a string:must not be hashed,
must not be
converted to UTF-8
, or another non-“canonical” representation,must not have its reference count changed,
must not be shared with code that might do one of the above.
This list is not exhaustive. Avoiding these uses is your responsibility; Python does not always check these requirements.
To avoid accidentally exposing a partially-written string object, prefer using the
PyUnicodeWriter
API, or one of thePyUnicode_From*
functions below.Added in version 3.3.
-
PyObject *PyUnicode_FromKindAndData(int kind, const void *buffer, Py_ssize_t size)¶
- Return value: New reference.
Create a new Unicode object with the given kind (possible values are
PyUnicode_1BYTE_KIND
etc., as returned byPyUnicode_KIND()
). The buffer must point to an array of size units of 1, 2 or 4 bytes per character, as given by the kind.If necessary, the input buffer is copied and transformed into the canonical representation. For example, if the buffer is a UCS4 string (
PyUnicode_4BYTE_KIND
) and it consists only of codepoints in the UCS1 range, it will be transformed into UCS1 (PyUnicode_1BYTE_KIND
).Added in version 3.3.
-
PyObject *PyUnicode_FromStringAndSize(const char *str, Py_ssize_t size)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object from the char buffer str. The bytes will be interpreted as being UTF-8 encoded. The buffer is copied into the new object. The return value might be a shared object, i.e. modification of the data is not allowed.
This function raises
SystemError
when:size < 0,
str is
NULL
and size > 0
Changed in version 3.12: str ==
NULL
with size > 0 is not allowed anymore.
-
PyObject *PyUnicode_FromString(const char *str)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object from a UTF-8 encoded null-terminated char buffer str.
-
PyObject *PyUnicode_FromFormat(const char *format, ...)¶
- Return value: New reference. Part of the Stable ABI.
Take a C
printf()
-style format string and a variable number of arguments, calculate the size of the resulting Python Unicode string and return a string with the values formatted into it. The variable arguments must be C types and must correspond exactly to the format characters in the format ASCII-encoded string.A conversion specifier contains two or more characters and has the following components, which must occur in this order:
The
'%'
character, which marks the start of the specifier.Conversion flags (optional), which affect the result of some conversion types.
Minimum field width (optional). If specified as an
'*'
(asterisk), the actual width is given in the next argument, which must be of type int, and the object to convert comes after the minimum field width and optional precision.Precision (optional), given as a
'.'
(dot) followed by the precision. If specified as'*'
(an asterisk), the actual precision is given in the next argument, which must be of type int, and the value to convert comes after the precision.Length modifier (optional).
Conversion type.
The conversion flag characters are:
Flag
Meaning
0
The conversion will be zero padded for numeric values.
-
The converted value is left adjusted (overrides the
0
flag if both are given).The length modifiers for following integer conversions (
d
,i
,o
,u
,x
, orX
) specify the type of the argument (int by default):Modifier
Types
l
long or unsigned long
ll
long long or unsigned long long
j
intmax_t
oruintmax_t
z
size_t
orssize_t
t
ptrdiff_t
The length modifier
l
for following conversionss
orV
specify that the type of the argument is const wchar_t*.The conversion specifiers are:
Conversion Specifier
Type
Comment
%
n/a
The literal
%
character.d
,i
Specified by the length modifier
The decimal representation of a signed C integer.
u
Specified by the length modifier
The decimal representation of an unsigned C integer.
o
Specified by the length modifier
The octal representation of an unsigned C integer.
x
Specified by the length modifier
The hexadecimal representation of an unsigned C integer (lowercase).
X
Specified by the length modifier
The hexadecimal representation of an unsigned C integer (uppercase).
c
int
A single character.
s
const char* or const wchar_t*
A null-terminated C character array.
p
const void*
The hex representation of a C pointer. Mostly equivalent to
printf("%p")
except that it is guaranteed to start with the literal0x
regardless of what the platform’sprintf
yields.A
The result of calling
ascii()
.U
A Unicode object.
V
PyObject*, const char* or const wchar_t*
A Unicode object (which may be
NULL
) and a null-terminated C character array as a second parameter (which will be used, if the first parameter isNULL
).S
The result of calling
PyObject_Str()
.R
The result of calling
PyObject_Repr()
.T
Get the fully qualified name of an object type; call
PyType_GetFullyQualifiedName()
.#T
Similar to
T
format, but use a colon (:
) as separator between the module name and the qualified name.N
Get the fully qualified name of a type; call
PyType_GetFullyQualifiedName()
.#N
Similar to
N
format, but use a colon (:
) as separator between the module name and the qualified name.Note
The width formatter unit is number of characters rather than bytes. The precision formatter unit is number of bytes or
wchar_t
items (if the length modifierl
is used) for"%s"
and"%V"
(if thePyObject*
argument isNULL
), and a number of characters for"%A"
,"%U"
,"%S"
,"%R"
and"%V"
(if thePyObject*
argument is notNULL
).Note
Unlike to C
printf()
the0
flag has effect even when a precision is given for integer conversions (d
,i
,u
,o
,x
, orX
).Changed in version 3.2: Support for
"%lld"
and"%llu"
added.Changed in version 3.3: Support for
"%li"
,"%lli"
and"%zi"
added.Changed in version 3.4: Support width and precision formatter for
"%s"
,"%A"
,"%U"
,"%V"
,"%S"
,"%R"
added.Changed in version 3.12: Support for conversion specifiers
o
andX
. Support for length modifiersj
andt
. Length modifiers are now applied to all integer conversions. Length modifierl
is now applied to conversion specifierss
andV
. Support for variable width and precision*
. Support for flag-
.An unrecognized format character now sets a
SystemError
. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded.Changed in version 3.13: Support for
%T
,%#T
,%N
and%#N
formats added.
-
PyObject *PyUnicode_FromFormatV(const char *format, va_list vargs)¶
- Return value: New reference. Part of the Stable ABI.
Identical to
PyUnicode_FromFormat()
except that it takes exactly two arguments.
-
PyObject *PyUnicode_FromObject(PyObject *obj)¶
- Return value: New reference. Part of the Stable ABI.
Copy an instance of a Unicode subtype to a new true Unicode object if necessary. If obj is already a true Unicode object (not a subtype), return a new strong reference to the object.
Objects other than Unicode or its subtypes will cause a
TypeError
.
-
PyObject *PyUnicode_FromOrdinal(int ordinal)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode Object from the given Unicode code point ordinal.
The ordinal must be in
range(0x110000)
. AValueError
is raised in the case it is not.
-
PyObject *PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Decode an encoded object obj to a Unicode object.
bytes
,bytearray
and other bytes-like objects are decoded according to the given encoding and using the error handling defined by errors. Both can beNULL
to have the interface use the default values (see Built-in Codecs for details).All other objects, including Unicode objects, cause a
TypeError
to be set.The API returns
NULL
if there was an error. The caller is responsible for decref’ing the returned objects.
-
void PyUnicode_Append(PyObject **p_left, PyObject *right)¶
- Part of the Stable ABI.
Append the string right to the end of p_left. p_left must point to a strong reference to a Unicode object;
PyUnicode_Append()
releases (“steals”) this reference.On error, set *p_left to
NULL
and set an exception.On success, set *p_left to a new strong reference to the result.
-
void PyUnicode_AppendAndDel(PyObject **p_left, PyObject *right)¶
- Part of the Stable ABI.
The function is similar to
PyUnicode_Append()
, with the only difference being that it decrements the reference count of right by one.
-
PyObject *PyUnicode_BuildEncodingMap(PyObject *string)¶
- Return value: New reference. Part of the Stable ABI.
Return a mapping suitable for decoding a custom single-byte encoding. Given a Unicode string string of up to 256 characters representing an encoding table, returns either a compact internal mapping object or a dictionary mapping character ordinals to byte values. Raises a
TypeError
and returnNULL
on invalid input.Added in version 3.2.
-
const char *PyUnicode_GetDefaultEncoding(void)¶
- Part of the Stable ABI.
Return the name of the default string encoding,
"utf-8"
. Seesys.getdefaultencoding()
.The returned string does not need to be freed, and is valid until interpreter shutdown.
-
Py_ssize_t PyUnicode_GetLength(PyObject *unicode)¶
- Part of the Stable ABI since version 3.7.
Return the length of the Unicode object, in code points.
On error, set an exception and return
-1
.Added in version 3.3.
-
Py_ssize_t PyUnicode_CopyCharacters(PyObject *to, Py_ssize_t to_start, PyObject *from, Py_ssize_t from_start, Py_ssize_t how_many)¶
Copy characters from one Unicode object into another. This function performs character conversion when necessary and falls back to
memcpy()
if possible. Returns-1
and sets an exception on error, otherwise returns the number of copied characters.The string must not have been “used” yet. See
PyUnicode_New()
for details.Added in version 3.3.
-
int PyUnicode_Resize(PyObject **unicode, Py_ssize_t length);¶
- Part of the Stable ABI.
Resize a Unicode object *unicode to the new length in code points.
Try to resize the string in place (which is usually faster than allocating a new string and copying characters), or create a new string.
*unicode is modified to point to the new (resized) object and
0
is returned on success. Otherwise,-1
is returned and an exception is set, and *unicode is left untouched.The function doesn’t check string content, the result may not be a string in canonical representation.
-
Py_ssize_t PyUnicode_Fill(PyObject *unicode, Py_ssize_t start, Py_ssize_t length, Py_UCS4 fill_char)¶
Fill a string with a character: write fill_char into
unicode[start:start+length]
.Fail if fill_char is bigger than the string maximum character, or if the string has more than 1 reference.
The string must not have been “used” yet. See
PyUnicode_New()
for details.Return the number of written character, or return
-1
and raise an exception on error.Added in version 3.3.
-
int PyUnicode_WriteChar(PyObject *unicode, Py_ssize_t index, Py_UCS4 character)¶
- Part of the Stable ABI since version 3.7.
Write a character to the string unicode at the zero-based index. Return
0
on success,-1
on error with an exception set.This function checks that unicode is a Unicode object, that the index is not out of bounds, and that the object’s reference count is one. See
PyUnicode_WRITE()
for a version that skips these checks, making them your responsibility.The string must not have been “used” yet. See
PyUnicode_New()
for details.Added in version 3.3.
-
Py_UCS4 PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)¶
- Part of the Stable ABI since version 3.7.
Read a character from a string. This function checks that unicode is a Unicode object and the index is not out of bounds, in contrast to
PyUnicode_READ_CHAR()
, which performs no error checking.Return character on success,
-1
on error with an exception set.Added in version 3.3.
-
PyObject *PyUnicode_Substring(PyObject *unicode, Py_ssize_t start, Py_ssize_t end)¶
- Return value: New reference. Part of the Stable ABI since version 3.7.
Return a substring of unicode, from character index start (included) to character index end (excluded). Negative indices are not supported. On error, set an exception and return
NULL
.Added in version 3.3.
-
Py_UCS4 *PyUnicode_AsUCS4(PyObject *unicode, Py_UCS4 *buffer, Py_ssize_t buflen, int copy_null)¶
- Part of the Stable ABI since version 3.7.
Copy the string unicode into a UCS4 buffer, including a null character, if copy_null is set. Returns
NULL
and sets an exception on error (in particular, aSystemError
if buflen is smaller than the length of unicode). buffer is returned on success.Added in version 3.3.
-
Py_UCS4 *PyUnicode_AsUCS4Copy(PyObject *unicode)¶
- Part of the Stable ABI since version 3.7.
Copy the string unicode into a new UCS4 buffer that is allocated using
PyMem_Malloc()
. If this fails,NULL
is returned with aMemoryError
set. The returned buffer always has an extra null code point appended.Added in version 3.3.
Locale Encoding¶
The current locale encoding can be used to decode text from the operating system.
-
PyObject *PyUnicode_DecodeLocaleAndSize(const char *str, Py_ssize_t length, const char *errors)¶
- Return value: New reference. Part of the Stable ABI since version 3.7.
Decode a string from UTF-8 on Android and VxWorks, or from the current locale encoding on other platforms. The supported error handlers are
"strict"
and"surrogateescape"
(PEP 383). The decoder uses"strict"
error handler if errors isNULL
. str must end with a null character but cannot contain embedded null characters.Use
PyUnicode_DecodeFSDefaultAndSize()
to decode a string from the filesystem encoding and error handler.This function ignores the Python UTF-8 Mode.
See also
The
Py_DecodeLocale()
function.Added in version 3.3.
Changed in version 3.7: The function now also uses the current locale encoding for the
surrogateescape
error handler, except on Android. Previously,Py_DecodeLocale()
was used for thesurrogateescape
, and the current locale encoding was used forstrict
.
-
PyObject *PyUnicode_DecodeLocale(const char *str, const char *errors)¶
- Return value: New reference. Part of the Stable ABI since version 3.7.
Similar to
PyUnicode_DecodeLocaleAndSize()
, but compute the string length usingstrlen()
.Added in version 3.3.
-
PyObject *PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)¶
- Return value: New reference. Part of the Stable ABI since version 3.7.
Encode a Unicode object to UTF-8 on Android and VxWorks, or to the current locale encoding on other platforms. The supported error handlers are
"strict"
and"surrogateescape"
(PEP 383). The encoder uses"strict"
error handler if errors isNULL
. Return abytes
object. unicode cannot contain embedded null characters.Use
PyUnicode_EncodeFSDefault()
to encode a string to the filesystem encoding and error handler.This function ignores the Python UTF-8 Mode.
See also
The
Py_EncodeLocale()
function.Added in version 3.3.
Changed in version 3.7: The function now also uses the current locale encoding for the
surrogateescape
error handler, except on Android. Previously,Py_EncodeLocale()
was used for thesurrogateescape
, and the current locale encoding was used forstrict
.
File System Encoding¶
Functions encoding to and decoding from the filesystem encoding and error handler (PEP 383 and PEP 529).
To encode file names to bytes
during argument parsing, the "O&"
converter should be used, passing PyUnicode_FSConverter()
as the
conversion function:
-
int PyUnicode_FSConverter(PyObject *obj, void *result)¶
- Part of the Stable ABI.
PyArg_Parse* converter: encode
str
objects – obtained directly or through theos.PathLike
interface – tobytes
usingPyUnicode_EncodeFSDefault()
;bytes
objects are output as-is. result must be an address of a C variable of type PyObject* (or PyBytesObject*). On success, set the variable to a new strong reference to a bytes object which must be released when it is no longer used and return a non-zero value (Py_CLEANUP_SUPPORTED
). Embedded null bytes are not allowed in the result. On failure, return0
with an exception set.If obj is
NULL
, the function releases a strong reference stored in the variable referred by result and returns1
.Added in version 3.1.
Changed in version 3.6: Accepts a path-like object.
To decode file names to str
during argument parsing, the "O&"
converter should be used, passing PyUnicode_FSDecoder()
as the
conversion function:
-
int PyUnicode_FSDecoder(PyObject *obj, void *result)¶
- Part of the Stable ABI.
PyArg_Parse* converter: decode
bytes
objects – obtained either directly or indirectly through theos.PathLike
interface – tostr
usingPyUnicode_DecodeFSDefaultAndSize()
;str
objects are output as-is. result must be an address of a C variable of type PyObject* (or PyUnicodeObject*). On success, set the variable to a new strong reference to a Unicode object which must be released when it is no longer used and return a non-zero value (Py_CLEANUP_SUPPORTED
). Embedded null characters are not allowed in the result. On failure, return0
with an exception set.If obj is
NULL
, release the strong reference to the object referred to by result and return1
.Added in version 3.2.
Changed in version 3.6: Accepts a path-like object.
-
PyObject *PyUnicode_DecodeFSDefaultAndSize(const char *str, Py_ssize_t size)¶
- Return value: New reference. Part of the Stable ABI.
Decode a string from the filesystem encoding and error handler.
If you need to decode a string from the current locale encoding, use
PyUnicode_DecodeLocaleAndSize()
.See also
The
Py_DecodeLocale()
function.Changed in version 3.6: The filesystem error handler is now used.
-
PyObject *PyUnicode_DecodeFSDefault(const char *str)¶
- Return value: New reference. Part of the Stable ABI.
Decode a null-terminated string from the filesystem encoding and error handler.
If the string length is known, use
PyUnicode_DecodeFSDefaultAndSize()
.Changed in version 3.6: The filesystem error handler is now used.
-
PyObject *PyUnicode_EncodeFSDefault(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object to the filesystem encoding and error handler, and return
bytes
. Note that the resultingbytes
object can contain null bytes.If you need to encode a string to the current locale encoding, use
PyUnicode_EncodeLocale()
.See also
The
Py_EncodeLocale()
function.Added in version 3.2.
Changed in version 3.6: The filesystem error handler is now used.
wchar_t Support¶
wchar_t
support for platforms which support it:
-
PyObject *PyUnicode_FromWideChar(const wchar_t *wstr, Py_ssize_t size)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object from the
wchar_t
buffer wstr of the given size. Passing-1
as the size indicates that the function must itself compute the length, usingwcslen()
. ReturnNULL
on failure.
-
Py_ssize_t PyUnicode_AsWideChar(PyObject *unicode, wchar_t *wstr, Py_ssize_t size)¶
- Part of the Stable ABI.
Copy the Unicode object contents into the
wchar_t
buffer wstr. At most sizewchar_t
characters are copied (excluding a possibly trailing null termination character). Return the number ofwchar_t
characters copied or-1
in case of an error.When wstr is
NULL
, instead return the size that would be required to store all of unicode including a terminating null.Note that the resulting wchar_t* string may or may not be null-terminated. It is the responsibility of the caller to make sure that the wchar_t* string is null-terminated in case this is required by the application. Also, note that the wchar_t* string might contain null characters, which would cause the string to be truncated when used with most C functions.
-
wchar_t *PyUnicode_AsWideCharString(PyObject *unicode, Py_ssize_t *size)¶
- Part of the Stable ABI since version 3.7.
Convert the Unicode object to a wide character string. The output string always ends with a null character. If size is not
NULL
, write the number of wide characters (excluding the trailing null termination character) into *size. Note that the resultingwchar_t
string might contain null characters, which would cause the string to be truncated when used with most C functions. If size isNULL
and the wchar_t* string contains null characters aValueError
is raised.Returns a buffer allocated by
PyMem_New
(usePyMem_Free()
to free it) on success. On error, returnsNULL
and *size is undefined. Raises aMemoryError
if memory allocation is failed.Added in version 3.2.
Changed in version 3.7: Raises a
ValueError
if size isNULL
and the wchar_t* string contains null characters.
Built-in Codecs¶
Python provides a set of built-in codecs which are written in C for speed. All of these codecs are directly usable via the following functions.
Many of the following APIs take two arguments encoding and errors, and they
have the same semantics as the ones of the built-in str()
string object
constructor.
Setting encoding to NULL
causes the default encoding to be used
which is UTF-8. The file system calls should use
PyUnicode_FSConverter()
for encoding file names. This uses the
filesystem encoding and error handler internally.
Error handling is set by errors which may also be set to NULL
meaning to use
the default handling defined for the codec. Default error handling for all
built-in codecs is “strict” (ValueError
is raised).
The codecs all use a similar interface. Only deviations from the following generic ones are documented for simplicity.
Generic Codecs¶
The following macro is provided:
-
Py_UNICODE_REPLACEMENT_CHARACTER¶
The Unicode code point
U+FFFD
(replacement character).This Unicode character is used as the replacement character during decoding if the errors argument is set to “replace”.
These are the generic codec APIs:
-
PyObject *PyUnicode_Decode(const char *str, Py_ssize_t size, const char *encoding, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the encoded string str. encoding and errors have the same meaning as the parameters of the same name in the
str()
built-in function. The codec to be used is looked up using the Python codec registry. ReturnNULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_AsEncodedString(PyObject *unicode, const char *encoding, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object and return the result as Python bytes object. encoding and errors have the same meaning as the parameters of the same name in the Unicode
encode()
method. The codec to be used is looked up using the Python codec registry. ReturnNULL
if an exception was raised by the codec.
UTF-8 Codecs¶
These are the UTF-8 codec APIs:
-
PyObject *PyUnicode_DecodeUTF8(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the UTF-8 encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_DecodeUTF8Stateful(const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)¶
- Return value: New reference. Part of the Stable ABI.
If consumed is
NULL
, behave likePyUnicode_DecodeUTF8()
. If consumed is notNULL
, trailing incomplete UTF-8 byte sequences will not be treated as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.
-
PyObject *PyUnicode_AsUTF8String(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object using UTF-8 and return the result as Python bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.The function fails if the string contains surrogate code points (
U+D800
-U+DFFF
).
-
const char *PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *size)¶
- Part of the Stable ABI since version 3.10.
Return a pointer to the UTF-8 encoding of the Unicode object, and store the size of the encoded representation (in bytes) in size. The size argument can be
NULL
; in this case no size will be stored. The returned buffer always has an extra null byte appended (not included in size), regardless of whether there are any other null code points.On error, set an exception, set size to
-1
(if it’s not NULL) and returnNULL
.The function fails if the string contains surrogate code points (
U+D800
-U+DFFF
).This caches the UTF-8 representation of the string in the Unicode object, and subsequent calls will return a pointer to the same buffer. The caller is not responsible for deallocating the buffer. The buffer is deallocated and pointers to it become invalid when the Unicode object is garbage collected.
Added in version 3.3.
Changed in version 3.7: The return type is now
const char *
rather ofchar *
.Changed in version 3.10: This function is a part of the limited API.
-
const char *PyUnicode_AsUTF8(PyObject *unicode)¶
As
PyUnicode_AsUTF8AndSize()
, but does not store the size.Warning
This function does not have any special behavior for null characters embedded within unicode. As a result, strings containing null characters will remain in the returned string, which some C functions might interpret as the end of the string, leading to truncation. If truncation is an issue, it is recommended to use
PyUnicode_AsUTF8AndSize()
instead.Added in version 3.3.
Changed in version 3.7: The return type is now
const char *
rather ofchar *
.
UTF-32 Codecs¶
These are the UTF-32 codec APIs:
-
PyObject *PyUnicode_DecodeUTF32(const char *str, Py_ssize_t size, const char *errors, int *byteorder)¶
- Return value: New reference. Part of the Stable ABI.
Decode size bytes from a UTF-32 encoded buffer string and return the corresponding Unicode object. errors (if non-
NULL
) defines the error handling. It defaults to “strict”.If byteorder is non-
NULL
, the decoder starts decoding using the given byte order:*byteorder == -1: little endian *byteorder == 0: native order *byteorder == 1: big endian
If
*byteorder
is zero, and the first four bytes of the input data are a byte order mark (BOM), the decoder switches to this byte order and the BOM is not copied into the resulting Unicode string. If*byteorder
is-1
or1
, any byte order mark is copied to the output.After completion, *byteorder is set to the current byte order at the end of input data.
If byteorder is
NULL
, the codec starts in native order mode.Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_DecodeUTF32Stateful(const char *str, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)¶
- Return value: New reference. Part of the Stable ABI.
If consumed is
NULL
, behave likePyUnicode_DecodeUTF32()
. If consumed is notNULL
,PyUnicode_DecodeUTF32Stateful()
will not treat trailing incomplete UTF-32 byte sequences (such as a number of bytes not divisible by four) as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.
-
PyObject *PyUnicode_AsUTF32String(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Return a Python byte string using the UTF-32 encoding in native byte order. The string always starts with a BOM mark. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
UTF-16 Codecs¶
These are the UTF-16 codec APIs:
-
PyObject *PyUnicode_DecodeUTF16(const char *str, Py_ssize_t size, const char *errors, int *byteorder)¶
- Return value: New reference. Part of the Stable ABI.
Decode size bytes from a UTF-16 encoded buffer string and return the corresponding Unicode object. errors (if non-
NULL
) defines the error handling. It defaults to “strict”.If byteorder is non-
NULL
, the decoder starts decoding using the given byte order:*byteorder == -1: little endian *byteorder == 0: native order *byteorder == 1: big endian
If
*byteorder
is zero, and the first two bytes of the input data are a byte order mark (BOM), the decoder switches to this byte order and the BOM is not copied into the resulting Unicode string. If*byteorder
is-1
or1
, any byte order mark is copied to the output (where it will result in either a\ufeff
or a\ufffe
character).After completion,
*byteorder
is set to the current byte order at the end of input data.If byteorder is
NULL
, the codec starts in native order mode.Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_DecodeUTF16Stateful(const char *str, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)¶
- Return value: New reference. Part of the Stable ABI.
If consumed is
NULL
, behave likePyUnicode_DecodeUTF16()
. If consumed is notNULL
,PyUnicode_DecodeUTF16Stateful()
will not treat trailing incomplete UTF-16 byte sequences (such as an odd number of bytes or a split surrogate pair) as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.
-
PyObject *PyUnicode_AsUTF16String(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Return a Python byte string using the UTF-16 encoding in native byte order. The string always starts with a BOM mark. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
UTF-7 Codecs¶
These are the UTF-7 codec APIs:
-
PyObject *PyUnicode_DecodeUTF7(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the UTF-7 encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_DecodeUTF7Stateful(const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)¶
- Return value: New reference. Part of the Stable ABI.
If consumed is
NULL
, behave likePyUnicode_DecodeUTF7()
. If consumed is notNULL
, trailing incomplete UTF-7 base-64 sections will not be treated as an error. Those bytes will not be decoded and the number of bytes that have been decoded will be stored in consumed.
Unicode-Escape Codecs¶
These are the “Unicode Escape” codec APIs:
-
PyObject *PyUnicode_DecodeUnicodeEscape(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the Unicode-Escape encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_AsUnicodeEscapeString(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object using Unicode-Escape and return the result as a bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
Raw-Unicode-Escape Codecs¶
These are the “Raw Unicode Escape” codec APIs:
-
PyObject *PyUnicode_DecodeRawUnicodeEscape(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the Raw-Unicode-Escape encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object using Raw-Unicode-Escape and return the result as a bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
Latin-1 Codecs¶
These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256 Unicode ordinals and only these are accepted by the codecs during encoding.
-
PyObject *PyUnicode_DecodeLatin1(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the Latin-1 encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_AsLatin1String(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object using Latin-1 and return the result as Python bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
ASCII Codecs¶
These are the ASCII codec APIs. Only 7-bit ASCII data is accepted. All other codes generate errors.
-
PyObject *PyUnicode_DecodeASCII(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the ASCII encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_AsASCIIString(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object using ASCII and return the result as Python bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
Character Map Codecs¶
This codec is special in that it can be used to implement many different codecs
(and this is in fact what was done to obtain most of the standard codecs
included in the encodings
package). The codec uses mappings to encode and
decode characters. The mapping objects provided must support the
__getitem__()
mapping interface; dictionaries and sequences work well.
These are the mapping codec APIs:
-
PyObject *PyUnicode_DecodeCharmap(const char *str, Py_ssize_t length, PyObject *mapping, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Create a Unicode object by decoding size bytes of the encoded string str using the given mapping object. Return
NULL
if an exception was raised by the codec.If mapping is
NULL
, Latin-1 decoding will be applied. Else mapping must map bytes ordinals (integers in the range from 0 to 255) to Unicode strings, integers (which are then interpreted as Unicode ordinals) orNone
. Unmapped data bytes – ones which cause aLookupError
, as well as ones which get mapped toNone
,0xFFFE
or'\ufffe'
, are treated as undefined mappings and cause an error.
-
PyObject *PyUnicode_AsCharmapString(PyObject *unicode, PyObject *mapping)¶
- Return value: New reference. Part of the Stable ABI.
Encode a Unicode object using the given mapping object and return the result as a bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.The mapping object must map Unicode ordinal integers to bytes objects, integers in the range from 0 to 255 or
None
. Unmapped character ordinals (ones which cause aLookupError
) as well as mapped toNone
are treated as “undefined mapping” and cause an error.
The following codec API is special in that maps Unicode to Unicode.
-
PyObject *PyUnicode_Translate(PyObject *unicode, PyObject *table, const char *errors)¶
- Return value: New reference. Part of the Stable ABI.
Translate a string by applying a character mapping table to it and return the resulting Unicode object. Return
NULL
if an exception was raised by the codec.The mapping table must map Unicode ordinal integers to Unicode ordinal integers or
None
(causing deletion of the character).Mapping tables need only provide the
__getitem__()
interface; dictionaries and sequences work well. Unmapped character ordinals (ones which cause aLookupError
) are left untouched and are copied as-is.errors has the usual meaning for codecs. It may be
NULL
which indicates to use the default error handling.
MBCS codecs for Windows¶
These are the MBCS codec APIs. They are currently only available on Windows and use the Win32 MBCS converters to implement the conversions. Note that MBCS (or DBCS) is a class of encodings, not just one. The target encoding is defined by the user settings on the machine running the codec.
-
PyObject *PyUnicode_DecodeMBCS(const char *str, Py_ssize_t size, const char *errors)¶
- Return value: New reference. Part of the Stable ABI on Windows since version 3.7.
Create a Unicode object by decoding size bytes of the MBCS encoded string str. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_DecodeMBCSStateful(const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)¶
- Return value: New reference. Part of the Stable ABI on Windows since version 3.7.
If consumed is
NULL
, behave likePyUnicode_DecodeMBCS()
. If consumed is notNULL
,PyUnicode_DecodeMBCSStateful()
will not decode trailing lead byte and the number of bytes that have been decoded will be stored in consumed.
-
PyObject *PyUnicode_DecodeCodePageStateful(int code_page, const char *str, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)¶
- Return value: New reference. Part of the Stable ABI on Windows since version 3.7.
Similar to
PyUnicode_DecodeMBCSStateful()
, except uses the code page specified by code_page.
-
PyObject *PyUnicode_AsMBCSString(PyObject *unicode)¶
- Return value: New reference. Part of the Stable ABI on Windows since version 3.7.
Encode a Unicode object using MBCS and return the result as Python bytes object. Error handling is “strict”. Return
NULL
if an exception was raised by the codec.
-
PyObject *PyUnicode_EncodeCodePage(int code_page, PyObject *unicode, const char *errors)¶
- Return value: New reference. Part of the Stable ABI on Windows since version 3.7.
Encode the Unicode object using the specified code page and return a Python bytes object. Return
NULL
if an exception was raised by the codec. UseCP_ACP
code page to get the MBCS encoder.Added in version 3.3.
Methods and Slot Functions¶
The following APIs are capable of handling Unicode objects and strings on input (we refer to them as strings in the descriptions) and return Unicode objects or integers as appropriate.
They all return NULL
or -1
if an exception occurs.
-
PyObject *PyUnicode_Concat(PyObject *left, PyObject *right)¶
- Return value: New reference. Part of the Stable ABI.
Concat two strings giving a new Unicode string.
-
PyObject *PyUnicode_Split(PyObject *unicode, PyObject *sep, Py_ssize_t maxsplit)¶
- Return value: New reference. Part of the Stable ABI.
Split a string giving a list of Unicode strings. If sep is
NULL
, splitting will be done at all whitespace substrings. Otherwise, splits occur at the given separator. At most maxsplit splits will be done. If negative, no limit is set. Separators are not included in the resulting list.On error, return
NULL
with an exception set.Equivalent to
str.split()
.
-
PyObject *PyUnicode_RSplit(PyObject *unicode, PyObject *sep, Py_ssize_t maxsplit)¶
- Return value: New reference. Part of the Stable ABI.
Similar to
PyUnicode_Split()
, but splitting will be done beginning at the end of the string.On error, return
NULL
with an exception set.Equivalent to
str.rsplit()
.
-
PyObject *PyUnicode_Splitlines(PyObject *unicode, int keepends)¶
- Return value: New reference. Part of the Stable ABI.
Split a Unicode string at line breaks, returning a list of Unicode strings. CRLF is considered to be one line break. If keepends is
0
, the Line break characters are not included in the resulting strings.
-
PyObject *PyUnicode_Partition(PyObject *unicode, PyObject *sep)¶
- Return value: New reference. Part of the Stable ABI.
Split a Unicode string at the first occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing the string itself, followed by two empty strings.
sep must not be empty.
On error, return
NULL
with an exception set.Equivalent to
str.partition()
.
-
PyObject *PyUnicode_RPartition(PyObject *unicode, PyObject *sep)¶
- Return value: New reference. Part of the Stable ABI.
Similar to
PyUnicode_Partition()
, but split a Unicode string at the last occurrence of sep. If the separator is not found, return a 3-tuple containing two empty strings, followed by the string itself.sep must not be empty.
On error, return
NULL
with an exception set.Equivalent to
str.rpartition()
.
-
PyObject *PyUnicode_Join(PyObject *separator, PyObject *seq)¶
- Return value: New reference. Part of the Stable ABI.
Join a sequence of strings using the given separator and return the resulting Unicode string.
-
Py_ssize_t PyUnicode_Tailmatch(PyObject *unicode, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)¶
- Part of the Stable ABI.
Return
1
if substr matchesunicode[start:end]
at the given tail end (direction ==-1
means to do a prefix match, direction ==1
a suffix match),0
otherwise. Return-1
if an error occurred.
-
Py_ssize_t PyUnicode_Find(PyObject *unicode, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)¶
- Part of the Stable ABI.
Return the first position of substr in
unicode[start:end]
using the given direction (direction ==1
means to do a forward search, direction ==-1
a backward search). The return value is the index of the first match; a value of-1
indicates that no match was found, and-2
indicates that an error occurred and an exception has been set.
-
Py_ssize_t PyUnicode_FindChar(PyObject *unicode, Py_UCS4 ch, Py_ssize_t start, Py_ssize_t end, int direction)¶
- Part of the Stable ABI since version 3.7.
Return the first position of the character ch in
unicode[start:end]
using the given direction (direction ==1
means to do a forward search, direction ==-1
a backward search). The return value is the index of the first match; a value of-1
indicates that no match was found, and-2
indicates that an error occurred and an exception has been set.Added in version 3.3.
Changed in version 3.7: start and end are now adjusted to behave like
unicode[start:end]
.
-
Py_ssize_t PyUnicode_Count(PyObject *unicode, PyObject *substr, Py_ssize_t start, Py_ssize_t end)¶
- Part of the Stable ABI.
Return the number of non-overlapping occurrences of substr in
unicode[start:end]
. Return-1
if an error occurred.
-
PyObject *PyUnicode_Replace(PyObject *unicode, PyObject *substr, PyObject *replstr, Py_ssize_t maxcount)¶
- Return value: New reference. Part of the Stable ABI.
Replace at most maxcount occurrences of substr in unicode with replstr and return the resulting Unicode object. maxcount ==
-1
means replace all occurrences.
-
int PyUnicode_Compare(PyObject *left, PyObject *right)¶
- Part of the Stable ABI.
Compare two strings and return
-1
,0
,1
for less than, equal, and greater than, respectively.This function returns
-1
upon failure, so one should callPyErr_Occurred()
to check for errors.See also
The
PyUnicode_Equal()
function.
-
int PyUnicode_Equal(PyObject *a, PyObject *b)¶
- Part of the Stable ABI since version 3.14.
Test if two strings are equal:
Return
1
if a is equal to b.Return
0
if a is not equal to b.Set a
TypeError
exception and return-1
if a or b is not astr
object.
The function always succeeds if a and b are
str
objects.The function works for
str
subclasses, but does not honor custom__eq__()
method.See also
The
PyUnicode_Compare()
function.Added in version 3.14.
-
int PyUnicode_EqualToUTF8AndSize(PyObject *unicode, const char *string, Py_ssize_t size)¶
- Part of the Stable ABI since version 3.13.
Compare a Unicode object with a char buffer which is interpreted as being UTF-8 or ASCII encoded and return true (
1
) if they are equal, or false (0
) otherwise. If the Unicode object contains surrogate code points (U+D800
-U+DFFF
) or the C string is not valid UTF-8, false (0
) is returned.This function does not raise exceptions.
Added in version 3.13.
-
int PyUnicode_EqualToUTF8(PyObject *unicode, const char *string)¶
- Part of the Stable ABI since version 3.13.
Similar to
PyUnicode_EqualToUTF8AndSize()
, but compute string length usingstrlen()
. If the Unicode object contains null characters, false (0
) is returned.Added in version 3.13.
-
int PyUnicode_CompareWithASCIIString(PyObject *unicode, const char *string)¶
- Part of the Stable ABI.
Compare a Unicode object, unicode, with string and return
-1
,0
,1
for less than, equal, and greater than, respectively. It is best to pass only ASCII-encoded strings, but the function interprets the input string as ISO-8859-1 if it contains non-ASCII characters.This function does not raise exceptions.
-
PyObject *PyUnicode_RichCompare(PyObject *left, PyObject *right, int op)¶
- Return value: New reference. Part of the Stable ABI.
Rich compare two Unicode strings and return one of the following:
NULL
in case an exception was raisedPy_NotImplemented
in case the type combination is unknown
Possible values for op are
Py_GT
,Py_GE
,Py_EQ
,Py_NE
,Py_LT
, andPy_LE
.
-
PyObject *PyUnicode_Format(PyObject *format, PyObject *args)¶
- Return value: New reference. Part of the Stable ABI.
Return a new string object from format and args; this is analogous to
format % args
.
-
int PyUnicode_Contains(PyObject *unicode, PyObject *substr)¶
- Part of the Stable ABI.
Check whether substr is contained in unicode and return true or false accordingly.
substr has to coerce to a one element Unicode string.
-1
is returned if there was an error.
-
void PyUnicode_InternInPlace(PyObject **p_unicode)¶
- Part of the Stable ABI.
Intern the argument *p_unicode in place. The argument must be the address of a pointer variable pointing to a Python Unicode string object. If there is an existing interned string that is the same as *p_unicode, it sets *p_unicode to it (releasing the reference to the old string object and creating a new strong reference to the interned string object), otherwise it leaves *p_unicode alone and interns it.
(Clarification: even though there is a lot of talk about references, think of this function as reference-neutral. You must own the object you pass in; after the call you no longer own the passed-in reference, but you newly own the result.)
This function never raises an exception. On error, it leaves its argument unchanged without interning it.
Instances of subclasses of
str
may not be interned, that is, PyUnicode_CheckExact(*p_unicode) must be true. If it is not, then – as with any other error – the argument is left unchanged.Note that interned strings are not “immortal”. You must keep a reference to the result to benefit from interning.
-
PyObject *PyUnicode_InternFromString(const char *str)¶
- Return value: New reference. Part of the Stable ABI.
A combination of
PyUnicode_FromString()
andPyUnicode_InternInPlace()
, meant for statically allocated strings.Return a new (“owned”) reference to either a new Unicode string object that has been interned, or an earlier interned string object with the same value.
Python may keep a reference to the result, or make it immortal, preventing it from being garbage-collected promptly. For interning an unbounded number of different strings, such as ones coming from user input, prefer calling
PyUnicode_FromString()
andPyUnicode_InternInPlace()
directly.
-
unsigned int PyUnicode_CHECK_INTERNED(PyObject *str)¶
Return a non-zero value if str is interned, zero if not. The str argument must be a string; this is not checked. This function always succeeds.
CPython implementation detail: A non-zero return value may carry additional information about how the string is interned. The meaning of such non-zero values, as well as each specific string’s intern-related details, may change between CPython versions.
PyUnicodeWriter¶
The PyUnicodeWriter
API can be used to create a Python str
object.
Added in version 3.14.
-
type PyUnicodeWriter¶
A Unicode writer instance.
The instance must be destroyed by
PyUnicodeWriter_Finish()
on success, orPyUnicodeWriter_Discard()
on error.
-
PyUnicodeWriter *PyUnicodeWriter_Create(Py_ssize_t length)¶
Create a Unicode writer instance.
length must be greater than or equal to
0
.If length is greater than
0
, preallocate an internal buffer of length characters.Set an exception and return
NULL
on error.
-
PyObject *PyUnicodeWriter_Finish(PyUnicodeWriter *writer)¶
Return the final Python
str
object and destroy the writer instance.Set an exception and return
NULL
on error.The writer instance is invalid after this call.
-
void PyUnicodeWriter_Discard(PyUnicodeWriter *writer)¶
Discard the internal Unicode buffer and destroy the writer instance.
If writer is
NULL
, no operation is performed.The writer instance is invalid after this call.
-
int PyUnicodeWriter_WriteChar(PyUnicodeWriter *writer, Py_UCS4 ch)¶
Write the single Unicode character ch into writer.
On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_WriteUTF8(PyUnicodeWriter *writer, const char *str, Py_ssize_t size)¶
Decode the string str from UTF-8 in strict mode and write the output into writer.
size is the string length in bytes. If size is equal to
-1
, callstrlen(str)
to get the string length.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.See also
PyUnicodeWriter_DecodeUTF8Stateful()
.
-
int PyUnicodeWriter_WriteASCII(PyUnicodeWriter *writer, const char *str, Py_ssize_t size)¶
Write the ASCII string str into writer.
size is the string length in bytes. If size is equal to
-1
, callstrlen(str)
to get the string length.str must only contain ASCII characters. The behavior is undefined if str contains non-ASCII characters.
On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.Added in version 3.14.
-
int PyUnicodeWriter_WriteWideChar(PyUnicodeWriter *writer, const wchar_t *str, Py_ssize_t size)¶
Write the wide string str into writer.
size is a number of wide characters. If size is equal to
-1
, callwcslen(str)
to get the string length.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_WriteUCS4(PyUnicodeWriter *writer, Py_UCS4 *str, Py_ssize_t size)¶
Writer the UCS4 string str into writer.
size is a number of UCS4 characters.
On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_WriteStr(PyUnicodeWriter *writer, PyObject *obj)¶
Call
PyObject_Str()
on obj and write the output into writer.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_WriteRepr(PyUnicodeWriter *writer, PyObject *obj)¶
Call
PyObject_Repr()
on obj and write the output into writer.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_WriteSubstring(PyUnicodeWriter *writer, PyObject *str, Py_ssize_t start, Py_ssize_t end)¶
Write the substring
str[start:end]
into writer.str must be Python
str
object. start must be greater than or equal to 0, and less than or equal to end. end must be less than or equal to str length.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_Format(PyUnicodeWriter *writer, const char *format, ...)¶
Similar to
PyUnicode_FromFormat()
, but write the output directly into writer.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.
-
int PyUnicodeWriter_DecodeUTF8Stateful(PyUnicodeWriter *writer, const char *string, Py_ssize_t length, const char *errors, Py_ssize_t *consumed)¶
Decode the string str from UTF-8 with errors error handler and write the output into writer.
size is the string length in bytes. If size is equal to
-1
, callstrlen(str)
to get the string length.errors is an error handler name, such as
"replace"
. If errors isNULL
, use the strict error handler.If consumed is not
NULL
, set *consumed to the number of decoded bytes on success. If consumed isNULL
, treat trailing incomplete UTF-8 byte sequences as an error.On success, return
0
. On error, set an exception, leave the writer unchanged, and return-1
.See also
PyUnicodeWriter_WriteUTF8()
.
Deprecated API¶
The following API is deprecated.
-
type Py_UNICODE¶
This is a typedef of
wchar_t
, which is a 16-bit type or 32-bit type depending on the platform. Please usewchar_t
directly instead.Changed in version 3.3: In previous versions, this was a 16-bit type or a 32-bit type depending on whether you selected a “narrow” or “wide” Unicode version of Python at build time.
Deprecated since version 3.13, will be removed in version 3.15.
-
int PyUnicode_READY(PyObject *unicode)¶
Do nothing and return
0
. This API is kept only for backward compatibility, but there are no plans to remove it.Added in version 3.3.
Deprecated since version 3.10: This API does nothing since Python 3.12. Previously, this needed to be called for each string created using the old API (
PyUnicode_FromUnicode()
or similar).
-
unsigned int PyUnicode_IS_READY(PyObject *unicode)¶
Do nothing and return
1
. This API is kept only for backward compatibility, but there are no plans to remove it.Added in version 3.3.
Deprecated since version 3.14: This API does nothing since Python 3.12. Previously, this could be called to check if
PyUnicode_READY()
is necessary.


Concrete Objects Layer

Concrete Objects Layer¶
The functions in this chapter are specific to certain Python object types.
Passing them an object of the wrong type is not a good idea; if you receive an
object from a Python program and you are not sure that it has the right type,
you must perform a type check first; for example, to check that an object is a
dictionary, use PyDict_Check()
. The chapter is structured like the
“family tree” of Python object types.
Warning
While the functions described in this chapter carefully check the type of the
objects which are passed in, many of them do not check for NULL
being passed
instead of a valid object. Allowing NULL
to be passed in can cause memory
access violations and immediate termination of the interpreter.
Fundamental Objects¶
This section describes Python type objects and the singleton object None
.
Numeric Objects¶
Sequence Objects¶
Generic operations on sequence objects were discussed in the previous chapter; this section deals with the specific kinds of sequence objects that are intrinsic to the Python language.
Container Objects¶
Function Objects¶
Other Objects¶
- File Objects
- Module Objects
- Module definitions
- Creating extension modules dynamically
- Support functions
- Iterator Objects
- Descriptor Objects
- Slice Objects
- MemoryView objects
- Pickle buffer objects
- Weak Reference Objects
- Capsules
- Frame Objects
- Generator Objects
- Coroutine Objects
- Context Variables Objects
- Objects for Type Hinting


Set Objects

Set Objects¶
This section details the public API for set
and frozenset
objects. Any functionality not listed below is best accessed using either
the abstract object protocol (including PyObject_CallMethod()
,
PyObject_RichCompareBool()
, PyObject_Hash()
,
PyObject_Repr()
, PyObject_IsTrue()
, PyObject_Print()
, and
PyObject_GetIter()
) or the abstract number protocol (including
PyNumber_And()
, PyNumber_Subtract()
, PyNumber_Or()
,
PyNumber_Xor()
, PyNumber_InPlaceAnd()
,
PyNumber_InPlaceSubtract()
, PyNumber_InPlaceOr()
, and
PyNumber_InPlaceXor()
).
-
type PySetObject¶
This subtype of
PyObject
is used to hold the internal data for bothset
andfrozenset
objects. It is like aPyDictObject
in that it is a fixed size for small sets (much like tuple storage) and will point to a separate, variable sized block of memory for medium and large sized sets (much like list storage). None of the fields of this structure should be considered public and all are subject to change. All access should be done through the documented API rather than by manipulating the values in the structure.
-
PyTypeObject PySet_Type¶
- Part of the Stable ABI.
This is an instance of
PyTypeObject
representing the Pythonset
type.
-
PyTypeObject PyFrozenSet_Type¶
- Part of the Stable ABI.
This is an instance of
PyTypeObject
representing the Pythonfrozenset
type.
The following type check macros work on pointers to any Python object. Likewise, the constructor functions work with any iterable Python object.
-
int PySet_Check(PyObject *p)¶
Return true if p is a
set
object or an instance of a subtype. This function always succeeds.
-
int PyFrozenSet_Check(PyObject *p)¶
Return true if p is a
frozenset
object or an instance of a subtype. This function always succeeds.
-
int PyAnySet_Check(PyObject *p)¶
Return true if p is a
set
object, afrozenset
object, or an instance of a subtype. This function always succeeds.
-
int PySet_CheckExact(PyObject *p)¶
Return true if p is a
set
object but not an instance of a subtype. This function always succeeds.Added in version 3.10.
-
int PyAnySet_CheckExact(PyObject *p)¶
Return true if p is a
set
object or afrozenset
object but not an instance of a subtype. This function always succeeds.
-
int PyFrozenSet_CheckExact(PyObject *p)¶
Return true if p is a
frozenset
object but not an instance of a subtype. This function always succeeds.
-
PyObject *PySet_New(PyObject *iterable)¶
- Return value: New reference. Part of the Stable ABI.
Return a new
set
containing objects returned by the iterable. The iterable may beNULL
to create a new empty set. Return the new set on success orNULL
on failure. RaiseTypeError
if iterable is not actually iterable. The constructor is also useful for copying a set (c=set(s)
).
-
PyObject *PyFrozenSet_New(PyObject *iterable)¶
- Return value: New reference. Part of the Stable ABI.
Return a new
frozenset
containing objects returned by the iterable. The iterable may beNULL
to create a new empty frozenset. Return the new set on success orNULL
on failure. RaiseTypeError
if iterable is not actually iterable.
The following functions and macros are available for instances of set
or frozenset
or instances of their subtypes.
-
Py_ssize_t PySet_Size(PyObject *anyset)¶
- Part of the Stable ABI.
Return the length of a
set
orfrozenset
object. Equivalent tolen(anyset)
. Raises aSystemError
if anyset is not aset
,frozenset
, or an instance of a subtype.
-
Py_ssize_t PySet_GET_SIZE(PyObject *anyset)¶
Macro form of
PySet_Size()
without error checking.
-
int PySet_Contains(PyObject *anyset, PyObject *key)¶
- Part of the Stable ABI.
Return
1
if found,0
if not found, and-1
if an error is encountered. Unlike the Python__contains__()
method, this function does not automatically convert unhashable sets into temporary frozensets. Raise aTypeError
if the key is unhashable. RaiseSystemError
if anyset is not aset
,frozenset
, or an instance of a subtype.
-
int PySet_Add(PyObject *set, PyObject *key)¶
- Part of the Stable ABI.
Add key to a
set
instance. Also works withfrozenset
instances (likePyTuple_SetItem()
it can be used to fill in the values of brand new frozensets before they are exposed to other code). Return0
on success or-1
on failure. Raise aTypeError
if the key is unhashable. Raise aMemoryError
if there is no room to grow. Raise aSystemError
if set is not an instance ofset
or its subtype.
The following functions are available for instances of set
or its
subtypes but not for instances of frozenset
or its subtypes.
-
int PySet_Discard(PyObject *set, PyObject *key)¶
- Part of the Stable ABI.
Return
1
if found and removed,0
if not found (no action taken), and-1
if an error is encountered. Does not raiseKeyError
for missing keys. Raise aTypeError
if the key is unhashable. Unlike the Pythondiscard()
method, this function does not automatically convert unhashable sets into temporary frozensets. RaiseSystemError
if set is not an instance ofset
or its subtype.
-
PyObject *PySet_Pop(PyObject *set)¶
- Return value: New reference. Part of the Stable ABI.
Return a new reference to an arbitrary object in the set, and removes the object from the set. Return
NULL
on failure. RaiseKeyError
if the set is empty. Raise aSystemError
if set is not an instance ofset
or its subtype.
-
int PySet_Clear(PyObject *set)¶
- Part of the Stable ABI.
Empty an existing set of all elements. Return
0
on success. Return-1
and raiseSystemError
if set is not an instance ofset
or its subtype.
Deprecated API¶
-
PySet_MINSIZE¶
A soft deprecated constant representing the size of an internal preallocated table inside
PySetObject
instances.This is documented solely for completeness, as there are no guarantees that a given version of CPython uses preallocated tables with a fixed size. In code that does not deal with unstable set internals,
PySet_MINSIZE
can be replaced with a small constant like8
.If looking for the size of a set, use
PySet_Size()
instead.


What’s New in Python

What’s New in Python¶
The “What’s New in Python” series of essays takes tours through the most important changes between major Python versions. They are a “must read” for anyone wishing to stay up-to-date after a new release.
- What’s new in Python 3.14
- What’s New In Python 3.13
- What’s New In Python 3.12
- What’s New In Python 3.11
- Summary – Release highlights
- New Features
- New Features Related to Type Hints
- Other Language Changes
- Other CPython Implementation Changes
- New Modules
- Improved Modules
- Optimizations
- Faster CPython
- CPython bytecode changes
- Deprecated
- Pending Removal in Python 3.12
- Removed
- Porting to Python 3.11
- Build Changes
- C API Changes
- Notable changes in 3.11.4
- Notable changes in 3.11.5
- What’s New In Python 3.10
- Summary – Release highlights
- New Features
- New Features Related to Type Hints
- Other Language Changes
- New Modules
- Improved Modules
- Optimizations
- Deprecated
- Removed
- Porting to Python 3.10
- CPython bytecode changes
- Build Changes
- C API Changes
- Notable security feature in 3.10.7
- Notable security feature in 3.10.8
- Notable changes in 3.10.12
- What’s New In Python 3.9
- Summary – Release highlights
- You should check for DeprecationWarning in your code
- New Features
- Other Language Changes
- New Modules
- Improved Modules
- Optimizations
- Deprecated
- Removed
- Porting to Python 3.9
- Build Changes
- C API Changes
- Notable changes in Python 3.9.1
- Notable changes in Python 3.9.2
- Notable changes in Python 3.9.3
- Notable changes in Python 3.9.5
- Notable security feature in 3.9.14
- Notable changes in 3.9.17
- What’s New In Python 3.8
- Summary – Release highlights
- New Features
- Other Language Changes
- New Modules
- Improved Modules
- Optimizations
- Build and C API Changes
- Deprecated
- API and Feature Removals
- Porting to Python 3.8
- Notable changes in Python 3.8.1
- Notable changes in Python 3.8.2
- Notable changes in Python 3.8.3
- Notable changes in Python 3.8.8
- Notable changes in Python 3.8.9
- Notable changes in Python 3.8.10
- Notable changes in Python 3.8.10
- Notable changes in Python 3.8.12
- Notable security feature in 3.8.14
- Notable changes in 3.8.17
- What’s New In Python 3.7
- Summary – Release Highlights
- New Features
- Other Language Changes
- New Modules
- Improved Modules
- C API Changes
- Build Changes
- Optimizations
- Other CPython Implementation Changes
- Deprecated Python Behavior
- Deprecated Python modules, functions and methods
- Deprecated functions and types of the C API
- Platform Support Removals
- API and Feature Removals
- Module Removals
- Windows-only Changes
- Porting to Python 3.7
- Notable changes in Python 3.7.1
- Notable changes in Python 3.7.2
- Notable changes in Python 3.7.6
- Notable changes in Python 3.7.10
- Notable changes in Python 3.7.11
- Notable security feature in 3.7.14
- What’s New In Python 3.6
- Summary – Release highlights
- New Features
- Other Language Changes
- New Modules
- Improved Modules
- Optimizations
- Build and C API Changes
- Other Improvements
- Deprecated
- Removed
- Porting to Python 3.6
- Notable changes in Python 3.6.2
- Notable changes in Python 3.6.4
- Notable changes in Python 3.6.5
- Notable changes in Python 3.6.7
- Notable changes in Python 3.6.10
- Notable changes in Python 3.6.13
- Notable changes in Python 3.6.14
- What’s New In Python 3.5
- What’s New In Python 3.4
- What’s New In Python 3.3
- Summary – Release highlights
- PEP 405: Virtual Environments
- PEP 420: Implicit Namespace Packages
- PEP 3118: New memoryview implementation and buffer protocol documentation
- PEP 393: Flexible String Representation
- PEP 397: Python Launcher for Windows
- PEP 3151: Reworking the OS and IO exception hierarchy
- PEP 380: Syntax for Delegating to a Subgenerator
- PEP 409: Suppressing exception context
- PEP 414: Explicit Unicode literals
- PEP 3155: Qualified name for classes and functions
- PEP 412: Key-Sharing Dictionary
- PEP 362: Function Signature Object
- PEP 421: Adding sys.implementation
- Using importlib as the Implementation of Import
- Other Language Changes
- A Finer-Grained Import Lock
- Builtin functions and types
- New Modules
- Improved Modules
- Optimizations
- Build and C API Changes
- Deprecated
- Porting to Python 3.3
- What’s New In Python 3.2
- PEP 384: Defining a Stable ABI
- PEP 389: Argparse Command Line Parsing Module
- PEP 391: Dictionary Based Configuration for Logging
- PEP 3148: The
concurrent.futures
module - PEP 3147: PYC Repository Directories
- PEP 3149: ABI Version Tagged .so Files
- PEP 3333: Python Web Server Gateway Interface v1.0.1
- Other Language Changes
- New, Improved, and Deprecated Modules
- Multi-threading
- Optimizations
- Unicode
- Codecs
- Documentation
- IDLE
- Code Repository
- Build and C API Changes
- Porting to Python 3.2
- What’s New In Python 3.1
- What’s New In Python 3.0
- What’s New in Python 2.7
- The Future for Python 2.x
- Changes to the Handling of Deprecation Warnings
- Python 3.1 Features
- PEP 372: Adding an Ordered Dictionary to collections
- PEP 378: Format Specifier for Thousands Separator
- PEP 389: The argparse Module for Parsing Command Lines
- PEP 391: Dictionary-Based Configuration For Logging
- PEP 3106: Dictionary Views
- PEP 3137: The memoryview Object
- Other Language Changes
- New and Improved Modules
- Build and C API Changes
- Other Changes and Fixes
- Porting to Python 2.7
- New Features Added to Python 2.7 Maintenance Releases
- Acknowledgements
- What’s New in Python 2.6
- Python 3.0
- Changes to the Development Process
- PEP 343: The ‘with’ statement
- PEP 366: Explicit Relative Imports From a Main Module
- PEP 370: Per-user
site-packages
Directory - PEP 371: The
multiprocessing
Package - PEP 3101: Advanced String Formatting
- PEP 3105:
print
As a Function - PEP 3110: Exception-Handling Changes
- PEP 3112: Byte Literals
- PEP 3116: New I/O Library
- PEP 3118: Revised Buffer Protocol
- PEP 3119: Abstract Base Classes
- PEP 3127: Integer Literal Support and Syntax
- PEP 3129: Class Decorators
- PEP 3141: A Type Hierarchy for Numbers
- Other Language Changes
- New and Improved Modules
- Deprecations and Removals
- Build and C API Changes
- Porting to Python 2.6
- Acknowledgements
- What’s New in Python 2.5
- PEP 308: Conditional Expressions
- PEP 309: Partial Function Application
- PEP 314: Metadata for Python Software Packages v1.1
- PEP 328: Absolute and Relative Imports
- PEP 338: Executing Modules as Scripts
- PEP 341: Unified try/except/finally
- PEP 342: New Generator Features
- PEP 343: The ‘with’ statement
- PEP 352: Exceptions as New-Style Classes
- PEP 353: Using ssize_t as the index type
- PEP 357: The ‘__index__’ method
- Other Language Changes
- New, Improved, and Removed Modules
- Build and C API Changes
- Porting to Python 2.5
- Acknowledgements
- What’s New in Python 2.4
- PEP 218: Built-In Set Objects
- PEP 237: Unifying Long Integers and Integers
- PEP 289: Generator Expressions
- PEP 292: Simpler String Substitutions
- PEP 318: Decorators for Functions and Methods
- PEP 322: Reverse Iteration
- PEP 324: New subprocess Module
- PEP 327: Decimal Data Type
- PEP 328: Multi-line Imports
- PEP 331: Locale-Independent Float/String Conversions
- Other Language Changes
- New, Improved, and Deprecated Modules
- Build and C API Changes
- Porting to Python 2.4
- Acknowledgements
- What’s New in Python 2.3
- PEP 218: A Standard Set Datatype
- PEP 255: Simple Generators
- PEP 263: Source Code Encodings
- PEP 273: Importing Modules from ZIP Archives
- PEP 277: Unicode file name support for Windows NT
- PEP 278: Universal Newline Support
- PEP 279: enumerate()
- PEP 282: The logging Package
- PEP 285: A Boolean Type
- PEP 293: Codec Error Handling Callbacks
- PEP 301: Package Index and Metadata for Distutils
- PEP 302: New Import Hooks
- PEP 305: Comma-separated Files
- PEP 307: Pickle Enhancements
- Extended Slices
- Other Language Changes
- New, Improved, and Deprecated Modules
- Pymalloc: A Specialized Object Allocator
- Build and C API Changes
- Other Changes and Fixes
- Porting to Python 2.3
- Acknowledgements
- What’s New in Python 2.2
- Introduction
- PEPs 252 and 253: Type and Class Changes
- PEP 234: Iterators
- PEP 255: Simple Generators
- PEP 237: Unifying Long Integers and Integers
- PEP 238: Changing the Division Operator
- Unicode Changes
- PEP 227: Nested Scopes
- New and Improved Modules
- Interpreter Changes and Fixes
- Other Changes and Fixes
- Acknowledgements
- What’s New in Python 2.1
- Introduction
- PEP 227: Nested Scopes
- PEP 236: __future__ Directives
- PEP 207: Rich Comparisons
- PEP 230: Warning Framework
- PEP 229: New Build System
- PEP 205: Weak References
- PEP 232: Function Attributes
- PEP 235: Importing Modules on Case-Insensitive Platforms
- PEP 217: Interactive Display Hook
- PEP 208: New Coercion Model
- PEP 241: Metadata in Python Packages
- New and Improved Modules
- Other Changes and Fixes
- Acknowledgements
- What’s New in Python 2.0
- Introduction
- What About Python 1.6?
- New Development Process
- Unicode
- List Comprehensions
- Augmented Assignment
- String Methods
- Garbage Collection of Cycles
- Other Core Changes
- Porting to 2.0
- Extending/Embedding Changes
- Distutils: Making Modules Easy to Install
- XML Modules
- Module changes
- New modules
- IDLE Improvements
- Deleted and Deprecated Modules
- Acknowledgements
The “Changelog” is an HTML version of the file built from the contents of the Misc/NEWS.d directory tree, which contains all nontrivial changes to Python for the current version.
- Changelog
- Python next
- Python 3.14.3 final
- Python 3.14.2 final
- Python 3.14.1 final
- Python 3.14.0 final
- Python 3.14.0 release candidate 3
- Python 3.14.0 release candidate 2
- Python 3.14.0 release candidate 1
- Python 3.14.0 beta 4
- Python 3.14.0 beta 3
- Python 3.14.0 beta 2
- Python 3.14.0 beta 1
- Python 3.14.0 alpha 7
- Python 3.14.0 alpha 6
- Python 3.14.0 alpha 5
- Python 3.14.0 alpha 4
- Python 3.14.0 alpha 3
- Python 3.14.0 alpha 2
- Python 3.14.0 alpha 1
- Python 3.13.0 beta 1
- Python 3.13.0 alpha 6
- Python 3.13.0 alpha 5
- Python 3.13.0 alpha 4
- Python 3.13.0 alpha 3
- Python 3.13.0 alpha 2
- Python 3.13.0 alpha 1
- Python 3.12.0 beta 1
- Python 3.12.0 alpha 7
- Python 3.12.0 alpha 6
- Python 3.12.0 alpha 5
- Python 3.12.0 alpha 4
- Python 3.12.0 alpha 3
- Python 3.12.0 alpha 2
- Python 3.12.0 alpha 1
- Python 3.11.0 beta 1
- Python 3.11.0 alpha 7
- Python 3.11.0 alpha 6
- Python 3.11.0 alpha 5
- Python 3.11.0 alpha 4
- Python 3.11.0 alpha 3
- Python 3.11.0 alpha 2
- Python 3.11.0 alpha 1
- Python 3.10.0 beta 1
- Python 3.10.0 alpha 7
- Python 3.10.0 alpha 6
- Python 3.10.0 alpha 5
- Python 3.10.0 alpha 4
- Python 3.10.0 alpha 3
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- Python 3.9.0 beta 1
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- Python 3.9.0 alpha 5
- Python 3.9.0 alpha 4
- Python 3.9.0 alpha 3
- Python 3.9.0 alpha 2
- Python 3.9.0 alpha 1
- Python 3.8.0 beta 1
- Python 3.8.0 alpha 4
- Python 3.8.0 alpha 3
- Python 3.8.0 alpha 2
- Python 3.8.0 alpha 1
- Python 3.7.0 final
- Python 3.7.0 release candidate 1
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- Python 3.7.0 beta 3
- Python 3.7.0 beta 2
- Python 3.7.0 beta 1
- Python 3.7.0 alpha 4
- Python 3.7.0 alpha 3
- Python 3.7.0 alpha 2
- Python 3.7.0 alpha 1
- Python 3.6.6 final
- Python 3.6.6 release candidate 1
- Python 3.6.5 final
- Python 3.6.5 release candidate 1
- Python 3.6.4 final
- Python 3.6.4 release candidate 1
- Python 3.6.3 final
- Python 3.6.3 release candidate 1
- Python 3.6.2 final
- Python 3.6.2 release candidate 2
- Python 3.6.2 release candidate 1
- Python 3.6.1 final
- Python 3.6.1 release candidate 1
- Python 3.6.0 final
- Python 3.6.0 release candidate 2
- Python 3.6.0 release candidate 1
- Python 3.6.0 beta 4
- Python 3.6.0 beta 3
- Python 3.6.0 beta 2
- Python 3.6.0 beta 1
- Python 3.6.0 alpha 4
- Python 3.6.0 alpha 3
- Python 3.6.0 alpha 2
- Python 3.6.0 alpha 1
- Python 3.5.5 final
- Python 3.5.5 release candidate 1
- Python 3.5.4 final
- Python 3.5.4 release candidate 1
- Python 3.5.3 final
- Python 3.5.3 release candidate 1
- Python 3.5.2 final
- Python 3.5.2 release candidate 1
- Python 3.5.1 final
- Python 3.5.1 release candidate 1
- Python 3.5.0 final
- Python 3.5.0 release candidate 4
- Python 3.5.0 release candidate 3
- Python 3.5.0 release candidate 2
- Python 3.5.0 release candidate 1
- Python 3.5.0 beta 4
- Python 3.5.0 beta 3
- Python 3.5.0 beta 2
- Python 3.5.0 beta 1
- Python 3.5.0 alpha 4
- Python 3.5.0 alpha 3
- Python 3.5.0 alpha 2
- Python 3.5.0 alpha 1


Introduction

1. Introduction¶
This reference manual describes the Python programming language. It is not intended as a tutorial.
While I am trying to be as precise as possible, I chose to use English rather than formal specifications for everything except syntax and lexical analysis. This should make the document more understandable to the average reader, but will leave room for ambiguities. Consequently, if you were coming from Mars and tried to re-implement Python from this document alone, you might have to guess things and in fact you would probably end up implementing quite a different language. On the other hand, if you are using Python and wonder what the precise rules about a particular area of the language are, you should definitely be able to find them here. If you would like to see a more formal definition of the language, maybe you could volunteer your time — or invent a cloning machine :-).
It is dangerous to add too many implementation details to a language reference document — the implementation may change, and other implementations of the same language may work differently. On the other hand, CPython is the one Python implementation in widespread use (although alternate implementations continue to gain support), and its particular quirks are sometimes worth being mentioned, especially where the implementation imposes additional limitations. Therefore, you’ll find short “implementation notes” sprinkled throughout the text.
Every Python implementation comes with a number of built-in and standard modules. These are documented in The Python Standard Library. A few built-in modules are mentioned when they interact in a significant way with the language definition.
1.1. Alternate Implementations¶
Though there is one Python implementation which is by far the most popular, there are some alternate implementations which are of particular interest to different audiences.
Known implementations include:
- CPython
This is the original and most-maintained implementation of Python, written in C. New language features generally appear here first.
- Jython
Python implemented in Java. This implementation can be used as a scripting language for Java applications, or can be used to create applications using the Java class libraries. It is also often used to create tests for Java libraries. More information can be found at the Jython website.
- Python for .NET
This implementation actually uses the CPython implementation, but is a managed .NET application and makes .NET libraries available. It was created by Brian Lloyd. For more information, see the Python for .NET home page.
- IronPython
An alternate Python for .NET. Unlike Python.NET, this is a complete Python implementation that generates IL, and compiles Python code directly to .NET assemblies. It was created by Jim Hugunin, the original creator of Jython. For more information, see the IronPython website.
- PyPy
An implementation of Python written completely in Python. It supports several advanced features not found in other implementations like stackless support and a Just in Time compiler. One of the goals of the project is to encourage experimentation with the language itself by making it easier to modify the interpreter (since it is written in Python). Additional information is available on the PyPy project’s home page.
Each of these implementations varies in some way from the language as documented in this manual, or introduces specific information beyond what’s covered in the standard Python documentation. Please refer to the implementation-specific documentation to determine what else you need to know about the specific implementation you’re using.
1.2. Notation¶
The descriptions of lexical analysis and syntax use a grammar notation that is a mixture of EBNF and PEG. For example:
name:letter
(letter
|digit
| "_")* letter: "a"..."z" | "A"..."Z" digit: "0"..."9"
In this example, the first line says that a name
is a letter
followed
by a sequence of zero or more letter
s, digit
s, and underscores.
A letter
in turn is any of the single characters 'a'
through
'z'
and A
through Z
; a digit
is a single character from 0
to 9
.
Each rule begins with a name (which identifies the rule that’s being defined)
followed by a colon, :
.
The definition to the right of the colon uses the following syntax elements:
name
: A name refers to another rule. Where possible, it is a link to the rule’s definition.TOKEN
: An uppercase name refers to a token. For the purposes of grammar definitions, tokens are the same as rules.
"text"
,'text'
: Text in single or double quotes must match literally (without the quotes). The type of quote is chosen according to the meaning oftext
:'if'
: A name in single quotes denotes a keyword."case"
: A name in double quotes denotes a soft-keyword.'@'
: A non-letter symbol in single quotes denotes anOP
token, that is, a delimiter or operator.
e1 e2
: Items separated only by whitespace denote a sequence. Here,e1
must be followed bye2
.e1 | e2
: A vertical bar is used to separate alternatives. It denotes PEG’s “ordered choice”: ife1
matches,e2
is not considered. In traditional PEG grammars, this is written as a slash,/
, rather than a vertical bar. See PEP 617 for more background and details.e*
: A star means zero or more repetitions of the preceding item.e+
: Likewise, a plus means one or more repetitions.[e]
: A phrase enclosed in square brackets means zero or one occurrences. In other words, the enclosed phrase is optional.e?
: A question mark has exactly the same meaning as square brackets: the preceding item is optional.(e)
: Parentheses are used for grouping.
The following notation is only used in lexical definitions.
"a"..."z"
: Two literal characters separated by three dots mean a choice of any single character in the given (inclusive) range of ASCII characters.<...>
: A phrase between angular brackets gives an informal description of the matched symbol (for example,<any ASCII character except "\">
), or an abbreviation that is defined in nearby text (for example,<Lu>
).
Some definitions also use lookaheads, which indicate that an element must (or must not) match at a given position, but without consuming any input:
&e
: a positive lookahead (that is,e
is required to match)!e
: a negative lookahead (that is,e
is required not to match)
The unary operators (*
, +
, ?
) bind as tightly as possible;
the vertical bar (|
) binds most loosely.
White space is only meaningful to separate tokens.
Rules are normally contained on a single line, but rules that are too long may be wrapped:
literal: stringliteral | bytesliteral | integer | floatnumber | imagnumber
Alternatively, rules may be formatted with the first line ending at the colon, and each alternative beginning with a vertical bar on a new line. For example:
literal: | stringliteral | bytesliteral | integer | floatnumber | imagnumber
This does not mean that there is an empty first alternative.
1.2.1. Lexical and Syntactic definitions¶
There is some difference between lexical and syntactic analysis: the lexical analyzer operates on the individual characters of the input source, while the parser (syntactic analyzer) operates on the stream of tokens generated by the lexical analysis. However, in some cases the exact boundary between the two phases is a CPython implementation detail.
The practical difference between the two is that in lexical definitions,
all whitespace is significant.
The lexical analyzer discards all whitespace that is not
converted to tokens like token.INDENT
or NEWLINE
.
Syntactic definitions then use these tokens, rather than source characters.
This documentation uses the same BNF grammar for both styles of definitions. All uses of BNF in the next chapter (Lexical analysis) are lexical definitions; uses in subsequent chapters are syntactic definitions.