
Unicode Objects and Codecs
**************************


Unicode Objects
===============


Unicode Type
------------

These are the basic Unicode object types used for the Unicode
implementation in Python:

Py_UNICODE

   This type represents the storage type which is used by Python
   internally as basis for holding Unicode ordinals.  Python's default
   builds use a 16-bit type for ``Py_UNICODE`` and store Unicode
   values internally as UCS2. It is also possible to build a UCS4
   version of Python (most recent Linux distributions come with UCS4
   builds of Python). These builds then use a 32-bit type for
   ``Py_UNICODE`` and store Unicode data internally as UCS4. On
   platforms where ``wchar_t`` is available and compatible with the
   chosen Python Unicode build variant, ``Py_UNICODE`` is a typedef
   alias for ``wchar_t`` to enhance native platform compatibility. On
   all other platforms, ``Py_UNICODE`` is a typedef alias for either
   ``unsigned short`` (UCS2) or ``unsigned long`` (UCS4).

Note that UCS2 and UCS4 Python builds are not binary compatible.
Please keep this in mind when writing extensions or interfaces.

PyUnicodeObject

   This subtype of ``PyObject`` represents a Python Unicode object.

PyTypeObject PyUnicode_Type

   This instance of ``PyTypeObject`` represents the Python Unicode
   type.  It is exposed to Python code as ``str``.

The following APIs are really C macros and can be used to do fast
checks and to access internal read-only data of Unicode objects:

int PyUnicode_Check(PyObject *o)

   Return true if the object *o* is a Unicode object or an instance of
   a Unicode subtype.

int PyUnicode_CheckExact(PyObject *o)

   Return true if the object *o* is a Unicode object, but not an
   instance of a subtype.

Py_ssize_t PyUnicode_GET_SIZE(PyObject *o)

   Return the size of the object.  *o* has to be a ``PyUnicodeObject``
   (not checked).

Py_ssize_t PyUnicode_GET_DATA_SIZE(PyObject *o)

   Return the size of the object's internal buffer in bytes.  *o* has
   to be a ``PyUnicodeObject`` (not checked).

Py_UNICODE* PyUnicode_AS_UNICODE(PyObject *o)

   Return a pointer to the internal ``Py_UNICODE`` buffer of the
   object.  *o* has to be a ``PyUnicodeObject`` (not checked).

const char* PyUnicode_AS_DATA(PyObject *o)

   Return a pointer to the internal buffer of the object. *o* has to
   be a ``PyUnicodeObject`` (not checked).

int PyUnicode_ClearFreeList()

   Clear the free list. Return the total number of freed items.


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_UNICODE ch)

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

int Py_UNICODE_ISLOWER(Py_UNICODE ch)

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

int Py_UNICODE_ISUPPER(Py_UNICODE ch)

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

int Py_UNICODE_ISTITLE(Py_UNICODE ch)

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

int Py_UNICODE_ISLINEBREAK(Py_UNICODE ch)

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

int Py_UNICODE_ISDECIMAL(Py_UNICODE ch)

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

int Py_UNICODE_ISDIGIT(Py_UNICODE ch)

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

int Py_UNICODE_ISNUMERIC(Py_UNICODE ch)

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

int Py_UNICODE_ISALPHA(Py_UNICODE ch)

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

int Py_UNICODE_ISALNUM(Py_UNICODE ch)

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

int Py_UNICODE_ISPRINTABLE(Py_UNICODE ch)

   Return 1 or 0 depending on whether *ch* is a printable character.
   Nonprintable characters are those characters defined in the Unicode
   character database as "Other" or "Separator", excepting the ASCII
   space (0x20) which is considered printable.  (Note that printable
   characters in this context are those which should not be escaped
   when ``repr()`` is invoked on a string. It has no bearing on the
   handling of strings written to ``sys.stdout`` or ``sys.stderr``.)

These APIs can be used for fast direct character conversions:

Py_UNICODE Py_UNICODE_TOLOWER(Py_UNICODE ch)

   Return the character *ch* converted to lower case.

Py_UNICODE Py_UNICODE_TOUPPER(Py_UNICODE ch)

   Return the character *ch* converted to upper case.

Py_UNICODE Py_UNICODE_TOTITLE(Py_UNICODE ch)

   Return the character *ch* converted to title case.

int Py_UNICODE_TODECIMAL(Py_UNICODE ch)

   Return the character *ch* converted to a decimal positive integer.
   Return ``-1`` if this is not possible.  This macro does not raise
   exceptions.

int Py_UNICODE_TODIGIT(Py_UNICODE ch)

   Return the character *ch* converted to a single digit integer.
   Return ``-1`` if this is not possible.  This macro does not raise
   exceptions.

double Py_UNICODE_TONUMERIC(Py_UNICODE ch)

   Return the character *ch* converted to a double. Return ``-1.0`` if
   this is not possible.  This macro does not raise exceptions.


Plain Py_UNICODE
----------------

To create Unicode objects and access their basic sequence properties,
use these APIs:

PyObject* PyUnicode_FromUnicode(const Py_UNICODE *u, Py_ssize_t size)
    Return value: New reference.

   Create a Unicode object from the Py_UNICODE buffer *u* of the given
   size. *u* may be *NULL* which causes the contents to be undefined.
   It is the user's responsibility to fill in the needed data.  The
   buffer is copied into the new object. If the buffer is not *NULL*,
   the return value might be a shared object. Therefore, modification
   of the resulting Unicode object is only allowed when *u* is *NULL*.

PyObject* PyUnicode_FromStringAndSize(const char *u, Py_ssize_t size)

   Create a Unicode object from the char buffer *u*.  The bytes will
   be interpreted as being UTF-8 encoded.  *u* may also be *NULL*
   which causes the contents to be undefined. It is the user's
   responsibility to fill in the needed data.  The buffer is copied
   into the new object. If the buffer is not *NULL*, the return value
   might be a shared object. Therefore, modification of the resulting
   Unicode object is only allowed when *u* is *NULL*.

PyObject *PyUnicode_FromString(const char *u)

   Create a Unicode object from an UTF-8 encoded null-terminated char
   buffer *u*.

PyObject* PyUnicode_FromFormat(const char *format, ...)

   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. The
   following format characters are allowed:

   +---------------------+-----------------------+----------------------------------+
   | Format Characters   | Type                  | Comment                          |
   +=====================+=======================+==================================+
   | ``%%``              | *n/a*                 | The literal % character.         |
   +---------------------+-----------------------+----------------------------------+
   | ``%c``              | int                   | A single character, represented  |
   |                     |                       | as an C int.                     |
   +---------------------+-----------------------+----------------------------------+
   | ``%d``              | int                   | Exactly equivalent to            |
   |                     |                       | ``printf("%d")``.                |
   +---------------------+-----------------------+----------------------------------+
   | ``%u``              | unsigned int          | Exactly equivalent to            |
   |                     |                       | ``printf("%u")``.                |
   +---------------------+-----------------------+----------------------------------+
   | ``%ld``             | long                  | Exactly equivalent to            |
   |                     |                       | ``printf("%ld")``.               |
   +---------------------+-----------------------+----------------------------------+
   | ``%lu``             | unsigned long         | Exactly equivalent to            |
   |                     |                       | ``printf("%lu")``.               |
   +---------------------+-----------------------+----------------------------------+
   | ``%lld``            | long long             | Exactly equivalent to            |
   |                     |                       | ``printf("%lld")``.              |
   +---------------------+-----------------------+----------------------------------+
   | ``%llu``            | unsigned long long    | Exactly equivalent to            |
   |                     |                       | ``printf("%llu")``.              |
   +---------------------+-----------------------+----------------------------------+
   | ``%zd``             | Py_ssize_t            | Exactly equivalent to            |
   |                     |                       | ``printf("%zd")``.               |
   +---------------------+-----------------------+----------------------------------+
   | ``%zu``             | size_t                | Exactly equivalent to            |
   |                     |                       | ``printf("%zu")``.               |
   +---------------------+-----------------------+----------------------------------+
   | ``%i``              | int                   | Exactly equivalent to            |
   |                     |                       | ``printf("%i")``.                |
   +---------------------+-----------------------+----------------------------------+
   | ``%x``              | int                   | Exactly equivalent to            |
   |                     |                       | ``printf("%x")``.                |
   +---------------------+-----------------------+----------------------------------+
   | ``%s``              | char*                 | A null-terminated C character    |
   |                     |                       | array.                           |
   +---------------------+-----------------------+----------------------------------+
   | ``%p``              | 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``              | PyObject*             | The result of calling            |
   |                     |                       | ``ascii()``.                     |
   +---------------------+-----------------------+----------------------------------+
   | ``%U``              | PyObject*             | A unicode object.                |
   +---------------------+-----------------------+----------------------------------+
   | ``%V``              | PyObject*, char *     | 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``              | PyObject*             | The result of calling            |
   |                     |                       | ``PyObject_Str()``.              |
   +---------------------+-----------------------+----------------------------------+
   | ``%R``              | PyObject*             | The result of calling            |
   |                     |                       | ``PyObject_Repr()``.             |
   +---------------------+-----------------------+----------------------------------+

   An unrecognized format character causes all the rest of the format
   string to be copied as-is to the result string, and any extra
   arguments discarded.

   Note: The *"%lld"* and *"%llu"* format specifiers are only available
     when ``HAVE_LONG_LONG`` is defined.

   Changed in version 3.2: Support for ``"%lld"`` and ``"%llu"``
   added.

PyObject* PyUnicode_FromFormatV(const char *format, va_list vargs)

   Identical to ``PyUnicode_FromFormat()`` except that it takes
   exactly two arguments.

PyObject* PyUnicode_TransformDecimalToASCII(Py_UNICODE *s, Py_ssize_t size)

   Create a Unicode object by replacing all decimal digits in
   ``Py_UNICODE`` buffer of the given size by ASCII digits 0--9
   according to their decimal value.  Return *NULL* if an exception
   occurs.

Py_UNICODE* PyUnicode_AsUnicode(PyObject *unicode)

   Return a read-only pointer to the Unicode object's internal
   ``Py_UNICODE`` buffer, *NULL* if *unicode* is not a Unicode object.

Py_UNICODE* PyUnicode_AsUnicodeCopy(PyObject *unicode)

   Create a copy of a unicode string ending with a nul character.
   Return *NULL* and raise a ``MemoryError`` exception on memory
   allocation failure, otherwise return a new allocated buffer (use
   ``PyMem_Free()`` to free the buffer).

   New in version 3.2.

Py_ssize_t PyUnicode_GetSize(PyObject *unicode)

   Return the length of the Unicode object.

PyObject* PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)
    Return value: New reference.

   Coerce an encoded object *obj* to an Unicode object and return a
   reference with incremented refcount.

   ``bytes``, ``bytearray`` and other char buffer compatible objects
   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 the next section 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.

PyObject* PyUnicode_FromObject(PyObject *obj)
    Return value: New reference.

   Shortcut for ``PyUnicode_FromEncodedObject(obj, NULL, "strict")``
   which is used throughout the interpreter whenever coercion to
   Unicode is needed.

If the platform supports ``wchar_t`` and provides a header file
wchar.h, Python can interface directly to this type using the
following functions. Support is optimized if Python's own
``Py_UNICODE`` type is identical to the system's ``wchar_t``.


File System Encoding
--------------------

To encode and decode file names and other environment strings,
``Py_FileSystemEncoding`` should be used as the encoding, and
``"surrogateescape"`` should be used as the error handler (**PEP
383**). To encode file names during argument parsing, the ``"O&"``
converter should be used, passing ``PyUnicode_FSConverter()`` as the
conversion function:

int PyUnicode_FSConverter(PyObject* obj, void* result)

   ParseTuple converter: encode ``str`` objects to ``bytes`` using
   ``PyUnicode_EncodeFSDefault()``; ``bytes`` objects are output as-
   is. *result* must be a ``PyBytesObject*`` which must be released
   when it is no longer used.

   New in version 3.1.

To decode file names during argument parsing, the ``"O&"`` converter
should be used, passing ``PyUnicode_FSDecoder()`` as the conversion
function:

int PyUnicode_FSDecoder(PyObject* obj, void* result)

   ParseTuple converter: decode ``bytes`` objects to ``str`` using
   ``PyUnicode_DecodeFSDefaultAndSize()``; ``str`` objects are output
   as-is. *result* must be a ``PyUnicodeObject*`` which must be
   released when it is no longer used.

   New in version 3.2.

PyObject* PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)

   Decode a string using ``Py_FileSystemDefaultEncoding`` and the
   ``'surrogateescape'`` error handler, or ``'strict'`` on Windows.

   If ``Py_FileSystemDefaultEncoding`` is not set, fall back to the
   locale encoding.

   Changed in version 3.2: Use ``'strict'`` error handler on Windows.

PyObject* PyUnicode_DecodeFSDefault(const char *s)

   Decode a null-terminated string using
   ``Py_FileSystemDefaultEncoding`` and the ``'surrogateescape'``
   error handler, or ``'strict'`` on Windows.

   If ``Py_FileSystemDefaultEncoding`` is not set, fall back to the
   locale encoding.

   Use ``PyUnicode_DecodeFSDefaultAndSize()`` if you know the string
   length.

   Changed in version 3.2: Use ``'strict'`` error handler on Windows.

PyObject* PyUnicode_EncodeFSDefault(PyObject *unicode)

   Encode a Unicode object to ``Py_FileSystemDefaultEncoding`` with
   the ``'surrogateescape'`` error handler, or ``'strict'`` on
   Windows, and return ``bytes``.

   If ``Py_FileSystemDefaultEncoding`` is not set, fall back to the
   locale encoding.

   New in version 3.2.


wchar_t Support
---------------

wchar_t support for platforms which support it:

PyObject* PyUnicode_FromWideChar(const wchar_t *w, Py_ssize_t size)
    Return value: New reference.

   Create a Unicode object from the ``wchar_t`` buffer *w* of the
   given size. Passing -1 as the size indicates that the function must
   itself compute the length, using wcslen. Return *NULL* on failure.

Py_ssize_t PyUnicode_AsWideChar(PyUnicodeObject *unicode, wchar_t *w, Py_ssize_t size)

   Copy the Unicode object contents into the ``wchar_t`` buffer *w*.
   At most *size* ``wchar_t`` characters are copied (excluding a
   possibly trailing 0-termination character).  Return the number of
   ``wchar_t`` characters copied or -1 in case of an error.  Note that
   the resulting ``wchar_t`` string may or may not be 0-terminated.
   It is the responsibility of the caller to make sure that the
   ``wchar_t`` string is 0-terminated in case this is required by the
   application.

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 nul character. If *size* is not *NULL*,
   write the number of wide characters (excluding the trailing
   0-termination character) into **size*.

   Returns a buffer allocated by ``PyMem_Alloc()`` (use
   ``PyMem_Free()`` to free it) on success. On error, returns *NULL*,
   **size* is undefined and raises a ``MemoryError``.

   New in version 3.2.


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.
These parameters encoding and errors 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 ASCII.  The file system calls should use
``PyUnicode_FSConverter()`` for encoding file names. This uses the
variable ``Py_FileSystemDefaultEncoding`` internally. This variable
should be treated as read-only: On some systems, it will be a pointer
to a static string, on others, it will change at run-time (such as
when the application invokes setlocale).

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 deviation from the
following generic ones are documented for simplicity.


Generic Codecs
--------------

These are the generic codec APIs:

PyObject* PyUnicode_Decode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the encoded
   string *s*. *encoding* and *errors* have the same meaning as the
   parameters of the same name in the ``unicode()`` built-in function.
   The codec to be used is looked up using the Python codec registry.
   Return *NULL* if an exception was raised by the codec.

PyObject* PyUnicode_Encode(const Py_UNICODE *s, Py_ssize_t size, const char *encoding, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size and return a
   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.  Return *NULL* if an exception was raised by the codec.

PyObject* PyUnicode_AsEncodedString(PyObject *unicode, const char *encoding, const char *errors)
    Return value: New reference.

   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.
   Return *NULL* if an exception was raised by the codec.


UTF-8 Codecs
------------

These are the UTF-8 codec APIs:

PyObject* PyUnicode_DecodeUTF8(const char *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the UTF-8
   encoded string *s*. Return *NULL* if an exception was raised by the
   codec.

PyObject* PyUnicode_DecodeUTF8Stateful(const char *s, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)
    Return value: New reference.

   If *consumed* is *NULL*, behave like ``PyUnicode_DecodeUTF8()``. If
   *consumed* is not *NULL*, 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_EncodeUTF8(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using UTF-8 and
   return a Python bytes object.  Return *NULL* if an exception was
   raised by the codec.

PyObject* PyUnicode_AsUTF8String(PyObject *unicode)
    Return value: New reference.

   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.


UTF-32 Codecs
-------------

These are the UTF-32 codec APIs:

PyObject* PyUnicode_DecodeUTF32(const char *s, Py_ssize_t size, const char *errors, int *byteorder)

   Decode *length* 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`` or ``1``, 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.

   In a narrow build codepoints outside the BMP will be decoded as
   surrogate pairs.

   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 *s, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)

   If *consumed* is *NULL*, behave like ``PyUnicode_DecodeUTF32()``.
   If *consumed* is not *NULL*, ``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_EncodeUTF32(const Py_UNICODE *s, Py_ssize_t size, const char *errors, int byteorder)

   Return a Python bytes object holding the UTF-32 encoded value of
   the Unicode data in *s*.  Output is written according to the
   following byte order:

      byteorder == -1: little endian
      byteorder == 0:  native byte order (writes a BOM mark)
      byteorder == 1:  big endian

   If byteorder is ``0``, the output string will always start with the
   Unicode BOM mark (U+FEFF). In the other two modes, no BOM mark is
   prepended.

   If *Py_UNICODE_WIDE* is not defined, surrogate pairs will be output
   as a single codepoint.

   Return *NULL* if an exception was raised by the codec.

PyObject* PyUnicode_AsUTF32String(PyObject *unicode)

   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 *s, Py_ssize_t size, const char *errors, int *byteorder)
    Return value: New reference.

   Decode *length* 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`` or ``1``, 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 *s, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)
    Return value: New reference.

   If *consumed* is *NULL*, behave like ``PyUnicode_DecodeUTF16()``.
   If *consumed* is not *NULL*, ``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_EncodeUTF16(const Py_UNICODE *s, Py_ssize_t size, const char *errors, int byteorder)
    Return value: New reference.

   Return a Python bytes object holding the UTF-16 encoded value of
   the Unicode data in *s*.  Output is written according to the
   following byte order:

      byteorder == -1: little endian
      byteorder == 0:  native byte order (writes a BOM mark)
      byteorder == 1:  big endian

   If byteorder is ``0``, the output string will always start with the
   Unicode BOM mark (U+FEFF). In the other two modes, no BOM mark is
   prepended.

   If *Py_UNICODE_WIDE* is defined, a single ``Py_UNICODE`` value may
   get represented as a surrogate pair. If it is not defined, each
   ``Py_UNICODE`` values is interpreted as an UCS-2 character.

   Return *NULL* if an exception was raised by the codec.

PyObject* PyUnicode_AsUTF16String(PyObject *unicode)
    Return value: New reference.

   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 *s, Py_ssize_t size, const char *errors)

   Create a Unicode object by decoding *size* bytes of the UTF-7
   encoded string *s*.  Return *NULL* if an exception was raised by
   the codec.

PyObject* PyUnicode_DecodeUTF7Stateful(const char *s, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)

   If *consumed* is *NULL*, behave like ``PyUnicode_DecodeUTF7()``.
   If *consumed* is not *NULL*, 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*.

PyObject* PyUnicode_EncodeUTF7(const Py_UNICODE *s, Py_ssize_t size, int base64SetO, int base64WhiteSpace, const char *errors)

   Encode the ``Py_UNICODE`` buffer of the given size using UTF-7 and
   return a Python bytes object.  Return *NULL* if an exception was
   raised by the codec.

   If *base64SetO* is nonzero, "Set O" (punctuation that has no
   otherwise special meaning) will be encoded in base-64.  If
   *base64WhiteSpace* is nonzero, whitespace will be encoded in
   base-64.  Both are set to zero for the Python "utf-7" codec.


Unicode-Escape Codecs
---------------------

These are the "Unicode Escape" codec APIs:

PyObject* PyUnicode_DecodeUnicodeEscape(const char *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the Unicode-
   Escape encoded string *s*.  Return *NULL* if an exception was
   raised by the codec.

PyObject* PyUnicode_EncodeUnicodeEscape(const Py_UNICODE *s, Py_ssize_t size)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using Unicode-
   Escape and return a Python string object.  Return *NULL* if an
   exception was raised by the codec.

PyObject* PyUnicode_AsUnicodeEscapeString(PyObject *unicode)
    Return value: New reference.

   Encode a Unicode object using Unicode-Escape and return the result
   as Python string 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 *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the Raw-
   Unicode-Escape encoded string *s*.  Return *NULL* if an exception
   was raised by the codec.

PyObject* PyUnicode_EncodeRawUnicodeEscape(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using Raw-
   Unicode-Escape and return a Python string object.  Return *NULL* if
   an exception was raised by the codec.

PyObject* PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)
    Return value: New reference.

   Encode a Unicode object using Raw-Unicode-Escape and return the
   result as Python string 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 *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the Latin-1
   encoded string *s*.  Return *NULL* if an exception was raised by
   the codec.

PyObject* PyUnicode_EncodeLatin1(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using Latin-1
   and return a Python bytes object.  Return *NULL* if an exception
   was raised by the codec.

PyObject* PyUnicode_AsLatin1String(PyObject *unicode)
    Return value: New reference.

   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 *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the ASCII
   encoded string *s*.  Return *NULL* if an exception was raised by
   the codec.

PyObject* PyUnicode_EncodeASCII(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using ASCII and
   return a Python bytes object.  Return *NULL* if an exception was
   raised by the codec.

PyObject* PyUnicode_AsASCIIString(PyObject *unicode)
    Return value: New reference.

   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
--------------------

These are the mapping codec APIs:

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 mapping to encode and decode characters.

Decoding mappings must map single string characters to single Unicode
characters, integers (which are then interpreted as Unicode ordinals)
or None (meaning "undefined mapping" and causing an error).

Encoding mappings must map single Unicode characters to single string
characters, integers (which are then interpreted as Latin-1 ordinals)
or None (meaning "undefined mapping" and causing an error).

The mapping objects provided must only support the __getitem__ mapping
interface.

If a character lookup fails with a LookupError, the character is
copied as-is meaning that its ordinal value will be interpreted as
Unicode or Latin-1 ordinal resp. Because of this, mappings only need
to contain those mappings which map characters to different code
points.

PyObject* PyUnicode_DecodeCharmap(const char *s, Py_ssize_t size, PyObject *mapping, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the encoded
   string *s* using the given *mapping* object.  Return *NULL* if an
   exception was raised by the codec. If *mapping* is *NULL* latin-1
   decoding will be done. Else it can be a dictionary mapping byte or
   a unicode string, which is treated as a lookup table. Byte values
   greater that the length of the string and U+FFFE "characters" are
   treated as "undefined mapping".

PyObject* PyUnicode_EncodeCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *mapping, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using the given
   *mapping* object and return a Python string object. Return *NULL*
   if an exception was raised by the codec.

PyObject* PyUnicode_AsCharmapString(PyObject *unicode, PyObject *mapping)
    Return value: New reference.

   Encode a Unicode object using the given *mapping* object and return
   the result as Python string object.  Error handling is "strict".
   Return *NULL* if an exception was raised by the codec.

The following codec API is special in that maps Unicode to Unicode.

PyObject* PyUnicode_TranslateCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *table, const char *errors)
    Return value: New reference.

   Translate a ``Py_UNICODE`` buffer of the given length by applying a
   character mapping *table* to it and return the resulting Unicode
   object.  Return *NULL* when 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 a ``LookupError``) are left untouched and are
   copied as-is.

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.


MBCS codecs for Windows
-----------------------

PyObject* PyUnicode_DecodeMBCS(const char *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Create a Unicode object by decoding *size* bytes of the MBCS
   encoded string *s*. Return *NULL* if an exception was raised by the
   codec.

PyObject* PyUnicode_DecodeMBCSStateful(const char *s, int size, const char *errors, int *consumed)

   If *consumed* is *NULL*, behave like ``PyUnicode_DecodeMBCS()``. If
   *consumed* is not *NULL*, ``PyUnicode_DecodeMBCSStateful()`` will
   not decode trailing lead byte and the number of bytes that have
   been decoded will be stored in *consumed*.

PyObject* PyUnicode_EncodeMBCS(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    Return value: New reference.

   Encode the ``Py_UNICODE`` buffer of the given size using MBCS and
   return a Python bytes object.  Return *NULL* if an exception was
   raised by the codec.

PyObject* PyUnicode_AsMBCSString(PyObject *unicode)
    Return value: New reference.

   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.


Methods & Slots
---------------


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.

   Concat two strings giving a new Unicode string.

PyObject* PyUnicode_Split(PyObject *s, PyObject *sep, Py_ssize_t maxsplit)
    Return value: New reference.

   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.

PyObject* PyUnicode_Splitlines(PyObject *s, int keepend)
    Return value: New reference.

   Split a Unicode string at line breaks, returning a list of Unicode
   strings. CRLF is considered to be one line break.  If *keepend* is
   0, the Line break characters are not included in the resulting
   strings.

PyObject* PyUnicode_Translate(PyObject *str, PyObject *table, const char *errors)
    Return value: New reference.

   Translate a string by applying a character mapping table to it and
   return the resulting Unicode object.

   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 a ``LookupError``) 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.

PyObject* PyUnicode_Join(PyObject *separator, PyObject *seq)
    Return value: New reference.

   Join a sequence of strings using the given separator and return the
   resulting Unicode string.

int PyUnicode_Tailmatch(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)

   Return 1 if *substr* matches *str*[*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 *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)

   Return the first position of *substr* in *str*[*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_Count(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end)

   Return the number of non-overlapping occurrences of *substr* in
   ``str[start:end]``.  Return ``-1`` if an error occurred.

PyObject* PyUnicode_Replace(PyObject *str, PyObject *substr, PyObject *replstr, Py_ssize_t maxcount)
    Return value: New reference.

   Replace at most *maxcount* occurrences of *substr* in *str* with
   *replstr* and return the resulting Unicode object. *maxcount* == -1
   means replace all occurrences.

int PyUnicode_Compare(PyObject *left, PyObject *right)

   Compare two strings and return -1, 0, 1 for less than, equal, and
   greater than, respectively.

int PyUnicode_CompareWithASCIIString(PyObject *uni, char *string)

   Compare a unicode object, *uni*, 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".

int PyUnicode_RichCompare(PyObject *left, PyObject *right, int op)

   Rich compare two unicode strings and return one of the following:

   * ``NULL`` in case an exception was raised

   * ``Py_True`` or ``Py_False`` for successful comparisons

   * ``Py_NotImplemented`` in case the type combination is unknown

   Note that ``Py_EQ`` and ``Py_NE`` comparisons can cause a
   ``UnicodeWarning`` in case the conversion of the arguments to
   Unicode fails with a ``UnicodeDecodeError``.

   Possible values for *op* are ``Py_GT``, ``Py_GE``, ``Py_EQ``,
   ``Py_NE``, ``Py_LT``, and ``Py_LE``.

PyObject* PyUnicode_Format(PyObject *format, PyObject *args)
    Return value: New reference.

   Return a new string object from *format* and *args*; this is
   analogous to ``format % args``.  The *args* argument must be a
   tuple.

int PyUnicode_Contains(PyObject *container, PyObject *element)

   Check whether *element* is contained in *container* and return true
   or false accordingly.

   *element* has to coerce to a one element Unicode string. ``-1`` is
   returned if there was an error.

void PyUnicode_InternInPlace(PyObject **string)

   Intern the argument **string* 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 **string*, it sets **string* to it (decrementing the reference
   count of the old string object and incrementing the reference count
   of the interned string object), otherwise it leaves **string* alone
   and interns it (incrementing its reference count). (Clarification:
   even though there is a lot of talk about reference counts, think of
   this function as reference-count-neutral; you own the object after
   the call if and only if you owned it before the call.)

PyObject* PyUnicode_InternFromString(const char *v)

   A combination of ``PyUnicode_FromString()`` and
   ``PyUnicode_InternInPlace()``, returning either a new unicode
   string object that has been interned, or a new ("owned") reference
   to an earlier interned string object with the same value.
