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7.3.2 Unicode Objects

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

`Py_UNICODE`
  This type represents a 16-bit unsigned storage type which is used by Python internally as basis for holding Unicode ordinals. On platforms where `wchar_t` is available and also has 16-bits, `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 `unsigned short`.

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

PyTypeObject `PyUnicode_Type`
  This instance of `PyTypeObject` represents the Python Unicode type.

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)
  Returns true if the object o is a Unicode object or an instance of a Unicode subtype. Changed in version 2.2: Allowed subtypes to be accepted.

int `PyUnicode_CheckExact`(PyObject *o)
  Returns true if the object o is a Unicode object, but not an instance of a subtype. New in version 2.2.

int `PyUnicode_GET_SIZE`(PyObject *o)
  Returns the size of the object. o has to be a `PyUnicodeObject` (not checked).

int `PyUnicode_GET_DATA_SIZE`(PyObject *o)
  Returns 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)
  Returns 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)
  Returns a pointer to the internal buffer of the object. o has to be a `PyUnicodeObject` (not checked).

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)
  Returns 1/0 depending on whether ch is a whitespace character.

int `Py_UNICODE_ISLOWER`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is a lowercase character.

int `Py_UNICODE_ISUPPER`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is an uppercase character.

int `Py_UNICODE_ISTITLE`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is a titlecase character.

int `Py_UNICODE_ISLINEBREAK`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is a linebreak character.

int `Py_UNICODE_ISDECIMAL`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is a decimal character.

int `Py_UNICODE_ISDIGIT`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is a digit character.

int `Py_UNICODE_ISNUMERIC`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is a numeric character.

int `Py_UNICODE_ISALPHA`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is an alphabetic character.

int `Py_UNICODE_ISALNUM`(Py_UNICODE ch)
  Returns 1/0 depending on whether ch is an alphanumeric character.

These APIs can be used for fast direct character conversions:

Py_UNICODE `Py_UNICODE_TOLOWER`(Py_UNICODE ch)
  Returns the character ch converted to lower case.

Py_UNICODE `Py_UNICODE_TOUPPER`(Py_UNICODE ch)
  Returns the character ch converted to upper case.

Py_UNICODE `Py_UNICODE_TOTITLE`(Py_UNICODE ch)
  Returns the character ch converted to title case.

int `Py_UNICODE_TODECIMAL`(Py_UNICODE ch)
  Returns the character ch converted to a decimal positive integer. Returns `-1` if this is not possible. Does not raise exceptions.

int `Py_UNICODE_TODIGIT`(Py_UNICODE ch)
  Returns the character ch converted to a single digit integer. Returns `-1` if this is not possible. Does not raise exceptions.

double `Py_UNICODE_TONUMERIC`(Py_UNICODE ch)
  Returns the character ch converted to a (positive) double. Returns `-1.0` if this is not possible. Does not raise exceptions.

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

PyObject* `PyUnicode_FromUnicode`(const Py_UNICODE *u, int 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`.

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.

int `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.

  Coercion is done in the following way:

  1. Unicode objects are passed back as-is with incremented refcount. Note: These cannot be decoded; passing a non-`NULL` value for encoding will result in a `TypeError`.

  2. String 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).

  3. All other objects cause an exception.

  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`.

PyObject* `PyUnicode_FromWideChar`(const wchar_t *w, int size)
  Return value: New reference.
  Create a Unicode object from the `whcar_t` buffer w of the given size. Returns `NULL` on failure.

int `PyUnicode_AsWideChar`(PyUnicodeObject *unicode, wchar_t *w, int size)
  Copies the Unicode object contents into the `whcar_t` buffer w. At most size `whcar_t` characters are copied. Returns the number of `whcar_t` characters copied or -1 in case of an error.

Subsections

- 7.3.2.1 Built-in Codecs
- 7.3.2.2 Methods and Slot Functions