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# 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 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")`.
  `%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.

PyObject* `PyUnicode_FromFormatV`(const char *format, va_list vargs)
  Identical to `PyUnicode_FromFormat()` except that it takes exactly two arguments.

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_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)

  Convert obj into result, using `Py_FileSystemDefaultEncoding`, and the `"surrogateescape"` error handler. result must be a `PyObject*`, return a `bytes()` object which must be released if it is no longer used.

  New in version 3.1.

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

  Decode a null-terminated string using `Py_FileSystemDefaultEncoding` and the `"surrogateescape"` error handler.

  If `Py_FileSystemDefaultEncoding` is not set, fall back to UTF-8.

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

PyObject* `PyUnicode_DecodeFSDefault`(const char *s)

  Decode a string using `Py_FileSystemDefaultEncoding` and the `"surrogateescape"` error handler.

  If `Py_FileSystemDefaultEncoding` is not set, fall back to UTF-8.

### 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.

## 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 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 s 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 s 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 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` 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 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` 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

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.

These are the mapping codec APIs:

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 size 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.

### 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 *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.

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.

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