.. highlight:: c

.. _unicodeobjects:

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.

.. impl-detail::

The internal buffer always includes an extra trailing null character for

compatibility with null terminated C strings. This extra character is not

counted in :c:func:`PyUnicode_GetLength` nor in the various *size* arguments

of the functions below.

.. note::

The :c:type:`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:

.. c:var:: PyTypeObject PyUnicode_Type

This instance of :c:type:`PyTypeObject` represents the Python Unicode type.

It is exposed to Python code as :py:class:`str`.

.. c:var:: PyTypeObject PyUnicodeIter_Type

This instance of :c:type:`PyTypeObject` represents the Python Unicode

iterator type. It is used to iterate over Unicode string objects.

.. c:type:: Py_UCS4

Py_UCS2

Py_UCS1

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 :c:type:`Py_UCS4`.

.. versionadded:: 3.3

.. c:type:: PyASCIIObject

PyCompactUnicodeObject

PyUnicodeObject

These subtypes of :c:type:`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 return :c:type:`PyObject` pointers.

.. versionadded:: 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.

.. c:namespace:: NULL

.. c:macro:: PyUnicode_IS_COMPACT(o)

True if *o* uses the :c:struct:`PyCompactUnicodeObject` structure.

.. versionadded:: 3.3

.. c:macro:: PyUnicode_IS_COMPACT_ASCII(o)

True if *o* uses the :c:struct:`PyASCIIObject` structure.

.. versionadded:: 3.3

The following APIs are C macros and static inlined functions for fast checks and

access to internal read-only data of Unicode objects:

.. c:function:: 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.

.. c:function:: 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.

.. c:function:: 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).

.. versionadded:: 3.3

.. c:function:: 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

:c:func:`PyUnicode_KIND` to select the right function.

.. versionadded:: 3.3

.. c:macro:: PyUnicode_1BYTE_KIND

PyUnicode_2BYTE_KIND

PyUnicode_4BYTE_KIND

Return values of the :c:func:`PyUnicode_KIND` macro.

.. versionadded:: 3.3

.. versionchanged:: 3.12

``PyUnicode_WCHAR_KIND`` has been removed.

.. c:function:: 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).

.. versionadded:: 3.3

.. c:function:: 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).

.. versionadded:: 3.3

.. c:function:: Py_UCS4 PyUnicode_READ(int kind, void *data, Py_ssize_t index)

Read a code point from a canonical representation *data* (as obtained with

:c:func:`PyUnicode_DATA`). No checks are performed.

.. impl-detail::

Accept reading the trailing null character at index

:c:func:`PyUnicode_GetLength`.

.. versionadded:: 3.3

.. c:function:: 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 :c:func:`PyUnicode_READ` if you

do multiple consecutive reads.

.. impl-detail::

Accept reading the trailing null character at index

:c:func:`PyUnicode_GetLength`.

.. versionadded:: 3.3

.. c:function:: 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.

.. versionadded:: 3.3

.. c:function:: int PyUnicode_IsIdentifier(PyObject *unicode)

Return ``1`` if the string is a valid identifier according to the language

definition, section :ref:`identifiers`. Return ``0`` otherwise.

.. versionchanged:: 3.9

The function does not call :c:func:`Py_FatalError` anymore if the string

is not ready.

.. c:function:: unsigned int PyUnicode_IS_ASCII(PyObject *unicode)

Return true if the string only contains ASCII characters.

Equivalent to :py:meth:`str.isascii`.

.. versionadded:: 3.2

.. c:function:: Py_hash_t PyUnstable_Unicode_GET_CACHED_HASH(PyObject *str)

If the hash of *str*, as returned by :c:func:`PyObject_Hash`, has been

cached and is immediately available, return it.

Otherwise, return ``-1`` *without* setting an exception.

If *str* is not a string (that is, if ``PyUnicode_Check(obj)``

is false), the behavior is undefined.

This function never fails with an exception.

Note that there are no guarantees on when an object's hash is cached,

and the (non-)existence of a cached hash does not imply that the string has

any other properties.

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.

.. c:function:: int Py_UNICODE_ISSPACE(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a whitespace character.

.. c:function:: int Py_UNICODE_ISLOWER(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a lowercase character.

.. c:function:: int Py_UNICODE_ISUPPER(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is an uppercase character.

.. c:function:: int Py_UNICODE_ISTITLE(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a titlecase character.

.. c:function:: int Py_UNICODE_ISLINEBREAK(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a linebreak character.

.. c:function:: int Py_UNICODE_ISDECIMAL(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a decimal character.

.. c:function:: int Py_UNICODE_ISDIGIT(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a digit character.

.. c:function:: int Py_UNICODE_ISNUMERIC(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a numeric character.

.. c:function:: int Py_UNICODE_ISALPHA(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is an alphabetic character.

.. c:function:: int Py_UNICODE_ISALNUM(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is an alphanumeric character.

.. c:function:: int Py_UNICODE_ISPRINTABLE(Py_UCS4 ch)

Return ``1`` or ``0`` depending on whether *ch* is a printable character,

in the sense of :meth:`str.isprintable`.

These APIs can be used for fast direct character conversions:

.. c:function:: Py_UCS4 Py_UNICODE_TOLOWER(Py_UCS4 ch)

Return the character *ch* converted to lower case.

.. c:function:: Py_UCS4 Py_UNICODE_TOUPPER(Py_UCS4 ch)

Return the character *ch* converted to upper case.

.. c:function:: Py_UCS4 Py_UNICODE_TOTITLE(Py_UCS4 ch)

Return the character *ch* converted to title case.

.. c:function:: 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.

.. c:function:: 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.

.. c:function:: 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:

.. c:function:: int Py_UNICODE_IS_SURROGATE(Py_UCS4 ch)

Check if *ch* is a surrogate (``0xD800 <= ch <= 0xDFFF``).

.. c:function:: int Py_UNICODE_IS_HIGH_SURROGATE(Py_UCS4 ch)

Check if *ch* is a high surrogate (``0xD800 <= ch <= 0xDBFF``).

.. c:function:: int Py_UNICODE_IS_LOW_SURROGATE(Py_UCS4 ch)

Check if *ch* is a low surrogate (``0xDC00 <= ch <= 0xDFFF``).

.. c:function:: Py_UCS4 Py_UNICODE_HIGH_SURROGATE(Py_UCS4 ch)

Return the high UTF-16 surrogate (``0xD800`` to ``0xDBFF``) for a Unicode

code point in the range ``[0x10000; 0x10FFFF]``.

.. c:function:: Py_UCS4 Py_UNICODE_LOW_SURROGATE(Py_UCS4 ch)

Return the low UTF-16 surrogate (``0xDC00`` to ``0xDFFF``) for a Unicode

code point in the range ``[0x10000; 0x10FFFF]``.

.. c:function:: Py_UCS4 Py_UNICODE_JOIN_SURROGATES(Py_UCS4 high, Py_UCS4 low)

Join two surrogate code points and return a single :c:type:`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:

.. c:function:: PyObject* PyUnicode_FromKindAndData(int kind, const void *buffer, \

Py_ssize_t size)

Create a new Unicode object with the given *kind* (possible values are

:c:macro:`PyUnicode_1BYTE_KIND` etc., as returned by

:c:func:`PyUnicode_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

(:c:macro:`PyUnicode_4BYTE_KIND`) and it consists only of codepoints in

the UCS1 range, it will be transformed into UCS1

(:c:macro:`PyUnicode_1BYTE_KIND`).

All characters must be in range [U+0000; U+10ffff]. If *kind* is

:c:macro:`PyUnicode_4BYTE_KIND` and the string contains invalid characters,

the behavior is undefined.

.. versionadded:: 3.3

.. c:function:: PyObject* PyUnicode_FromStringAndSize(const char *str, Py_ssize_t size)

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 :exc:`SystemError` when:

* *size* < 0,

* *str* is ``NULL`` and *size* > 0

.. versionchanged:: 3.12

*str* == ``NULL`` with *size* > 0 is not allowed anymore.

.. c:function:: PyObject *PyUnicode_FromString(const char *str)

Create a Unicode object from a UTF-8 encoded null-terminated char buffer

*str*.

.. c:function:: PyObject* PyUnicode_FromFormat(const char *format, ...)

Take a C :c:func:`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 :c:expr:`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 :c:expr:`int`, and the value to

convert comes after the precision.

#. Length modifier (optional).

#. Conversion type.

The conversion flag characters are:

.. tabularcolumns:: |l|L|

+-------+-------------------------------------------------------------+

| 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``, or ``X``) specify the type of the argument

(:c:expr:`int` by default):

.. tabularcolumns:: |l|L|

+----------+-----------------------------------------------------+

| Modifier | Types |

+==========+=====================================================+

| ``l`` | :c:expr:`long` or :c:expr:`unsigned long` |

+----------+-----------------------------------------------------+

| ``ll`` | :c:expr:`long long` or :c:expr:`unsigned long long` |

+----------+-----------------------------------------------------+

| ``j`` | :c:type:`intmax_t` or :c:type:`uintmax_t` |

+----------+-----------------------------------------------------+

| ``z`` | :c:type:`size_t` or :c:type:`ssize_t` |

+----------+-----------------------------------------------------+

| ``t`` | :c:type:`ptrdiff_t` |

+----------+-----------------------------------------------------+

The length modifier ``l`` for following conversions ``s`` or ``V`` specify

that the type of the argument is :c:expr:`const wchar_t*`.

The conversion specifiers are:

.. list-table::

:widths: auto

:header-rows: 1

* - 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``

- :c:expr:`int`

- A single character.

* - ``s``

- :c:expr:`const char*` or :c:expr:`const wchar_t*`

- A null-terminated C character array.

* - ``p``

- :c:expr:`const void*`

- The hex representation of a C pointer.

Mostly equivalent to ``printf("%p")`` except that it is guaranteed to

start with the literal ``0x`` regardless of what the platform's

``printf`` yields.

* - ``A``

- :c:expr:`PyObject*`

- The result of calling :func:`ascii`.

* - ``U``

- :c:expr:`PyObject*`

- A Unicode object.

* - ``V``

- :c:expr:`PyObject*`, :c:expr:`const char*` or :c:expr:`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 is ``NULL``).

* - ``S``

- :c:expr:`PyObject*`

- The result of calling :c:func:`PyObject_Str`.

* - ``R``

- :c:expr:`PyObject*`

- The result of calling :c:func:`PyObject_Repr`.

* - ``T``

- :c:expr:`PyObject*`

- Get the fully qualified name of an object type;

call :c:func:`PyType_GetFullyQualifiedName`.

* - ``#T``

- :c:expr:`PyObject*`

- Similar to ``T`` format, but use a colon (``:``) as separator between

the module name and the qualified name.

* - ``N``

- :c:expr:`PyTypeObject*`

- Get the fully qualified name of a type;

call :c:func:`PyType_GetFullyQualifiedName`.

* - ``#N``

- :c:expr:`PyTypeObject*`

- 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 :c:type:`wchar_t`

items (if the length modifier ``l`` is used) for ``"%s"`` and

``"%V"`` (if the ``PyObject*`` argument is ``NULL``), and a number of

characters for ``"%A"``, ``"%U"``, ``"%S"``, ``"%R"`` and ``"%V"``

(if the ``PyObject*`` argument is not ``NULL``).

.. note::

Unlike to C :c:func:`printf` the ``0`` flag has effect even when

a precision is given for integer conversions (``d``, ``i``, ``u``, ``o``,

``x``, or ``X``).

.. versionchanged:: 3.2

Support for ``"%lld"`` and ``"%llu"`` added.

.. versionchanged:: 3.3

Support for ``"%li"``, ``"%lli"`` and ``"%zi"`` added.

.. versionchanged:: 3.4

Support width and precision formatter for ``"%s"``, ``"%A"``, ``"%U"``,

``"%V"``, ``"%S"``, ``"%R"`` added.

.. versionchanged:: 3.12

Support for conversion specifiers ``o`` and ``X``.

Support for length modifiers ``j`` and ``t``.

Length modifiers are now applied to all integer conversions.

Length modifier ``l`` is now applied to conversion specifiers ``s`` and ``V``.

Support for variable width and precision ``*``.

Support for flag ``-``.

An unrecognized format character now sets a :exc:`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.

.. versionchanged:: 3.13

Support for ``%T``, ``%#T``, ``%N`` and ``%#N`` formats added.

.. c:function:: PyObject* PyUnicode_FromFormatV(const char *format, va_list vargs)

Identical to :c:func:`PyUnicode_FromFormat` except that it takes exactly two

arguments.

.. c:function:: PyObject* PyUnicode_FromObject(PyObject *obj)

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 :term:`strong reference` to the object.

Objects other than Unicode or its subtypes will cause a :exc:`TypeError`.

.. c:function:: PyObject* PyUnicode_FromOrdinal(int ordinal)

Create a Unicode Object from the given Unicode code point *ordinal*.

The ordinal must be in ``range(0x110000)``. A :exc:`ValueError` is

raised in the case it is not.

.. c:function:: PyObject* PyUnicode_FromEncodedObject(PyObject *obj, \

const char *encoding, const char *errors)

Decode an encoded object *obj* to a Unicode object.

:class:`bytes`, :class:`bytearray` and other

:term:`bytes-like objects <bytes-like object>`

are decoded according to the given *encoding* and using the error handling

defined by *errors*. Both can be ``NULL`` to have the interface use the default

values (see :ref:`builtincodecs` for details).

All other objects, including Unicode objects, cause a :exc:`TypeError` to be

set.

The API returns ``NULL`` if there was an error. The caller is responsible for

decref'ing the returned objects.

.. c:function:: void PyUnicode_Append(PyObject **p_left, PyObject *right)

Append the string *right* to the end of *p_left*.

*p_left* must point to a :term:`strong reference` to a Unicode object;

:c:func:`!PyUnicode_Append` releases (":term:`steals <steal>`")

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.

.. c:function:: void PyUnicode_AppendAndDel(PyObject **p_left, PyObject *right)

The function is similar to :c:func:`PyUnicode_Append`, with the only

difference being that it decrements the reference count of *right* by one.

.. c:function:: PyObject* PyUnicode_BuildEncodingMap(PyObject* string)

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 :exc:`TypeError` and

return ``NULL`` on invalid input.

.. versionadded:: 3.2

.. c:function:: const char* PyUnicode_GetDefaultEncoding(void)

Return the name of the default string encoding, ``"utf-8"``.

See :func:`sys.getdefaultencoding`.

The returned string does not need to be freed, and is valid

until interpreter shutdown.

.. c:function:: Py_ssize_t PyUnicode_GetLength(PyObject *unicode)

Return the length of the Unicode object, in code points.

On error, set an exception and return ``-1``.

.. impl-detail::

The length does not count the trailing null character.

.. versionadded:: 3.3

.. c:function:: Py_UCS4 PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)

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

:c:func:`PyUnicode_READ_CHAR`, which performs no error checking.

Return character on success, ``-1`` on error with an exception set.

.. impl-detail::

Do not accept reading the trailing null character at index

:c:func:`PyUnicode_GetLength`.

.. versionadded:: 3.3

.. c:function:: PyObject* PyUnicode_Substring(PyObject *unicode, Py_ssize_t start, \

Py_ssize_t end)

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``.

.. versionadded:: 3.3

.. c:function:: Py_UCS4* PyUnicode_AsUCS4(PyObject *unicode, Py_UCS4 *buffer, \

Py_ssize_t buflen, int copy_null)

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, a :exc:`SystemError` if *buflen* is smaller than the length of

*unicode*). *buffer* is returned on success.

.. versionadded:: 3.3

.. c:function:: Py_UCS4* PyUnicode_AsUCS4Copy(PyObject *unicode)

Copy the string *unicode* into a new UCS4 buffer that is allocated using

:c:func:`PyMem_Malloc`. If this fails, ``NULL`` is returned with a

:exc:`MemoryError` set. The returned buffer always has an extra

null code point appended.

.. versionadded:: 3.3

Locale Encoding

"""""""""""""""

The current locale encoding can be used to decode text from the operating

system.

.. c:function:: PyObject* PyUnicode_DecodeLocaleAndSize(const char *str, \

Py_ssize_t length, \

const char *errors)

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* is ``NULL``. *str* must end with a null character but

cannot contain embedded null characters.

Use :c:func:`PyUnicode_DecodeFSDefaultAndSize` to decode a string from

the :term:`filesystem encoding and error handler`.

This function ignores the :ref:`Python UTF-8 Mode <utf8-mode>`.

.. seealso::

The :c:func:`Py_DecodeLocale` function.

.. versionadded:: 3.3

.. versionchanged:: 3.7

The function now also uses the current locale encoding for the

``surrogateescape`` error handler, except on Android. Previously, :c:func:`Py_DecodeLocale`

was used for the ``surrogateescape``, and the current locale encoding was

used for ``strict``.

.. c:function:: PyObject* PyUnicode_DecodeLocale(const char *str, const char *errors)

Similar to :c:func:`PyUnicode_DecodeLocaleAndSize`, but compute the string

length using :c:func:`!strlen`.

.. versionadded:: 3.3

.. c:function:: PyObject* PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)

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* is ``NULL``. Return a :class:`bytes` object. *unicode* cannot

contain embedded null characters.

Use :c:func:`PyUnicode_EncodeFSDefault` to encode a string to the

:term:`filesystem encoding and error handler`.

This function ignores the :ref:`Python UTF-8 Mode <utf8-mode>`.

.. seealso::

The :c:func:`Py_EncodeLocale` function.

.. versionadded:: 3.3

.. versionchanged:: 3.7

The function now also uses the current locale encoding for the

``surrogateescape`` error handler, except on Android. Previously,

:c:func:`Py_EncodeLocale`

was used for the ``surrogateescape``, and the current locale encoding was

used for ``strict``.

.. _capi-filesystem-encoding:

File System Encoding

""""""""""""""""""""

Functions encoding to and decoding from the :term:`filesystem encoding and

error handler` (:pep:`383` and :pep:`529`).

To encode file names to :class:`bytes` during argument parsing, the ``"O&"``

converter should be used, passing :c:func:`!PyUnicode_FSConverter` as the

conversion function:

.. c:function:: int PyUnicode_FSConverter(PyObject* obj, void* result)

:ref:`PyArg_Parse\* converter <arg-parsing>`: encode :class:`str` objects -- obtained directly or

through the :class:`os.PathLike` interface -- to :class:`bytes` using

:c:func:`PyUnicode_EncodeFSDefault`; :class:`bytes` objects are output as-is.

*result* must be an address of a C variable of type :c:expr:`PyObject*`

(or :c:expr:`PyBytesObject*`).

On success, set the variable to a new :term:`strong reference` to

a :ref:`bytes object <bytesobjects>` which must be released

when it is no longer used and return a non-zero value

(:c:macro:`Py_CLEANUP_SUPPORTED`).

Embedded null bytes are not allowed in the result.

On failure, return ``0`` with an exception set.

If *obj* is ``NULL``, the function releases a strong reference

stored in the variable referred by *result* and returns ``1``.

.. versionadded:: 3.1

.. versionchanged:: 3.6

Accepts a :term:`path-like object`.

To decode file names to :class:`str` during argument parsing, the ``"O&"``

converter should be used, passing :c:func:`!PyUnicode_FSDecoder` as the

conversion function:

.. c:function:: int PyUnicode_FSDecoder(PyObject* obj, void* result)

:ref:`PyArg_Parse\* converter <arg-parsing>`: decode :class:`bytes` objects -- obtained either

directly or indirectly through the :class:`os.PathLike` interface -- to

:class:`str` using :c:func:`PyUnicode_DecodeFSDefaultAndSize`; :class:`str`

objects are output as-is.

*result* must be an address of a C variable of type :c:expr:`PyObject*`

(or :c:expr:`PyUnicodeObject*`).

On success, set the variable to a new :term:`strong reference` to

a :ref:`Unicode object <unicodeobjects>` which must be released

when it is no longer used and return a non-zero value

(:c:macro:`Py_CLEANUP_SUPPORTED`).

Embedded null characters are not allowed in the result.

On failure, return ``0`` with an exception set.

If *obj* is ``NULL``, release the strong reference

to the object referred to by *result* and return ``1``.

.. versionadded:: 3.2

.. versionchanged:: 3.6

Accepts a :term:`path-like object`.

.. c:function:: PyObject* PyUnicode_DecodeFSDefaultAndSize(const char *str, Py_ssize_t size)

Decode a string from the :term:`filesystem encoding and error handler`.

If you need to decode a string from the current locale encoding, use

:c:func:`PyUnicode_DecodeLocaleAndSize`.

.. seealso::

The :c:func:`Py_DecodeLocale` function.

.. versionchanged:: 3.6

The :term:`filesystem error handler <filesystem encoding and error

handler>` is now used.

.. c:function:: PyObject* PyUnicode_DecodeFSDefault(const char *str)

Decode a null-terminated string from the :term:`filesystem encoding and

error handler`.

If the string length is known, use

:c:func:`PyUnicode_DecodeFSDefaultAndSize`.

.. versionchanged:: 3.6

The :term:`filesystem error handler <filesystem encoding and error

handler>` is now used.

.. c:function:: PyObject* PyUnicode_EncodeFSDefault(PyObject *unicode)

Encode a Unicode object to the :term:`filesystem encoding and error

handler`, and return :class:`bytes`. Note that the resulting :class:`bytes`

object can contain null bytes.

If you need to encode a string to the current locale encoding, use

:c:func:`PyUnicode_EncodeLocale`.

.. seealso::

The :c:func:`Py_EncodeLocale` function.

.. versionadded:: 3.2

.. versionchanged:: 3.6

The :term:`filesystem error handler <filesystem encoding and error

handler>` is now used.

wchar_t Support

"""""""""""""""

:c:type:`wchar_t` support for platforms which support it:

.. c:function:: PyObject* PyUnicode_FromWideChar(const wchar_t *wstr, Py_ssize_t size)

Create a Unicode object from the :c:type:`wchar_t` buffer *wstr* of the given *size*.

Passing ``-1`` as the *size* indicates that the function must itself compute the length,

using :c:func:`!wcslen`.

Return ``NULL`` on failure.

.. c:function:: Py_ssize_t PyUnicode_AsWideChar(PyObject *unicode, wchar_t *wstr, Py_ssize_t size)

Copy the Unicode object contents into the :c:type:`wchar_t` buffer *wstr*. At most

*size* :c:type:`wchar_t` characters are copied (excluding a possibly trailing

null termination character). Return the number of :c:type:`wchar_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 :c:expr:`wchar_t*`

string may or may not be null-terminated. It is the responsibility of the caller

to make sure that the :c:expr:`wchar_t*` string is null-terminated in case this is

required by the application. Also, note that the :c:expr:`wchar_t*` string

might contain null characters, which would cause the string to be truncated

when used with most C functions.

.. c:function:: wchar_t* PyUnicode_AsWideCharString(PyObject *unicode, Py_ssize_t *size)

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 resulting :c:type:`wchar_t` string might contain

null characters, which would cause the string to be truncated when used with

most C functions. If *size* is ``NULL`` and the :c:expr:`wchar_t*` string

contains null characters a :exc:`ValueError` is raised.

Returns a buffer allocated by :c:macro:`PyMem_New` (use

:c:func:`PyMem_Free` to free it) on success. On error, returns ``NULL``

and *\*size* is undefined. Raises a :exc:`MemoryError` if memory allocation

is failed.

.. versionadded:: 3.2

.. versionchanged:: 3.7

Raises a :exc:`ValueError` if *size* is ``NULL`` and the :c:expr:`wchar_t*`

string contains null characters.

.. _builtincodecs:

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 :func:`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

:c:func:`PyUnicode_FSConverter` for encoding file names. This uses the

:term:`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" (:exc:`ValueError` is raised).

The codecs all use a similar interface. Only deviations from the following

generic ones are documented for simplicity.