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


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

Since the implementation of **PEP 393** in Python 3.3, Unicode objects
internally use a variety of representations, in order to allow
handling the complete range of Unicode characters while staying memory
efficient.  There are special cases for strings where all code points
are below 128, 256, or 65536; otherwise, code points must be below
1114112 (which is the full Unicode range).

UTF-8 representation is created on demand and cached in the Unicode
object.

Note:

  The "Py_UNICODE" representation has been removed since Python 3.12
  with deprecated APIs. See **PEP 623** for more information.


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

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

type Py_UCS4
type Py_UCS2
type Py_UCS1
    * Part of the Stable ABI.*

   These types are typedefs for unsigned integer types wide enough to
   contain characters of 32 bits, 16 bits and 8 bits, respectively.
   When dealing with single Unicode characters, use "Py_UCS4".

   New in version 3.3.

type Py_UNICODE

   This is a typedef of wchar_t, which is a 16-bit type or 32-bit type
   depending on the platform.

   Changed in version 3.3: In previous versions, this was a 16-bit
   type or a 32-bit type depending on whether you selected a "narrow"
   or "wide" Unicode version of Python at build time.

type PyASCIIObject
type PyCompactUnicodeObject
type PyUnicodeObject

   These subtypes of "PyObject" represent a Python Unicode object.  In
   almost all cases, they shouldn't be used directly, since all API
   functions that deal with Unicode objects take and return "PyObject"
   pointers.

   New in version 3.3.

PyTypeObject PyUnicode_Type
    * Part of the Stable ABI.*

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

The following APIs are C macros and static inlined functions for fast
checks and access to internal read-only data of Unicode objects:

int PyUnicode_Check(PyObject *o)

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

int PyUnicode_CheckExact(PyObject *o)

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

int PyUnicode_READY(PyObject *o)

   Returns "0". This API is kept only for backward compatibility.

   New in version 3.3.

   Deprecated since version 3.10: This API does nothing since Python
   3.12.

Py_ssize_t PyUnicode_GET_LENGTH(PyObject *o)

   Return the length of the Unicode string, in code points.  *o* has
   to be a Unicode object in the "canonical" representation (not
   checked).

   New in version 3.3.

Py_UCS1 *PyUnicode_1BYTE_DATA(PyObject *o)
Py_UCS2 *PyUnicode_2BYTE_DATA(PyObject *o)
Py_UCS4 *PyUnicode_4BYTE_DATA(PyObject *o)

   Return a pointer to the canonical representation cast to UCS1, UCS2
   or UCS4 integer types for direct character access.  No checks are
   performed if the canonical representation has the correct character
   size; use "PyUnicode_KIND()" to select the right function.

   New in version 3.3.

PyUnicode_1BYTE_KIND
PyUnicode_2BYTE_KIND
PyUnicode_4BYTE_KIND

   Return values of the "PyUnicode_KIND()" macro.

   New in version 3.3.

   Changed in version 3.12: "PyUnicode_WCHAR_KIND" has been removed.

int PyUnicode_KIND(PyObject *o)

   Return one of the PyUnicode kind constants (see above) that
   indicate how many bytes per character this Unicode object uses to
   store its data.  *o* has to be a Unicode object in the "canonical"
   representation (not checked).

   New in version 3.3.

void *PyUnicode_DATA(PyObject *o)

   Return a void pointer to the raw Unicode buffer.  *o* has to be a
   Unicode object in the "canonical" representation (not checked).

   New in version 3.3.

void PyUnicode_WRITE(int kind, void *data, Py_ssize_t index, Py_UCS4 value)

   Write into a canonical representation *data* (as obtained with
   "PyUnicode_DATA()").  This function performs no sanity checks, and
   is intended for usage in loops.  The caller should cache the *kind*
   value and *data* pointer as obtained from other calls.  *index* is
   the index in the string (starts at 0) and *value* is the new code
   point value which should be written to that location.

   New in version 3.3.

Py_UCS4 PyUnicode_READ(int kind, void *data, Py_ssize_t index)

   Read a code point from a canonical representation *data* (as
   obtained with "PyUnicode_DATA()").  No checks or ready calls are
   performed.

   New in version 3.3.

Py_UCS4 PyUnicode_READ_CHAR(PyObject *o, Py_ssize_t index)

   Read a character from a Unicode object *o*, which must be in the
   "canonical" representation.  This is less efficient than
   "PyUnicode_READ()" if you do multiple consecutive reads.

   New in version 3.3.

Py_UCS4 PyUnicode_MAX_CHAR_VALUE(PyObject *o)

   Return the maximum code point that is suitable for creating another
   string based on *o*, which must be in the "canonical"
   representation.  This is always an approximation but more efficient
   than iterating over the string.

   New in version 3.3.

int PyUnicode_IsIdentifier(PyObject *o)
    * Part of the Stable ABI.*

   Return "1" if the string is a valid identifier according to the
   language definition, section Identifiers and keywords. Return "0"
   otherwise.

   Changed in version 3.9: The function does not call
   "Py_FatalError()" anymore if the string is not ready.


Unicode Character Properties
----------------------------

Unicode provides many different character properties. The most often
needed ones are available through these macros which are mapped to C
functions depending on the Python configuration.

int Py_UNICODE_ISSPACE(Py_UCS4 ch)

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

int Py_UNICODE_ISLOWER(Py_UCS4 ch)

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

int Py_UNICODE_ISUPPER(Py_UCS4 ch)

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

int Py_UNICODE_ISTITLE(Py_UCS4 ch)

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

int Py_UNICODE_ISLINEBREAK(Py_UCS4 ch)

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

int Py_UNICODE_ISDECIMAL(Py_UCS4 ch)

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

int Py_UNICODE_ISDIGIT(Py_UCS4 ch)

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

int Py_UNICODE_ISNUMERIC(Py_UCS4 ch)

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

int Py_UNICODE_ISALPHA(Py_UCS4 ch)

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

int Py_UNICODE_ISALNUM(Py_UCS4 ch)

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

int Py_UNICODE_ISPRINTABLE(Py_UCS4 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_UCS4 Py_UNICODE_TOLOWER(Py_UCS4 ch)

   Return the character *ch* converted to lower case.

   Deprecated since version 3.3: This function uses simple case
   mappings.

Py_UCS4 Py_UNICODE_TOUPPER(Py_UCS4 ch)

   Return the character *ch* converted to upper case.

   Deprecated since version 3.3: This function uses simple case
   mappings.

Py_UCS4 Py_UNICODE_TOTITLE(Py_UCS4 ch)

   Return the character *ch* converted to title case.

   Deprecated since version 3.3: This function uses simple case
   mappings.

int Py_UNICODE_TODECIMAL(Py_UCS4 ch)

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

int Py_UNICODE_TODIGIT(Py_UCS4 ch)

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

double Py_UNICODE_TONUMERIC(Py_UCS4 ch)

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

These APIs can be used to work with surrogates:

int Py_UNICODE_IS_SURROGATE(Py_UCS4 ch)

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

int Py_UNICODE_IS_HIGH_SURROGATE(Py_UCS4 ch)

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

int Py_UNICODE_IS_LOW_SURROGATE(Py_UCS4 ch)

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

Py_UCS4 Py_UNICODE_JOIN_SURROGATES(Py_UCS4 high, Py_UCS4 low)

   Join two surrogate characters and return a single "Py_UCS4" value.
   *high* and *low* are respectively the leading and trailing
   surrogates in a surrogate pair. *high* must be in the range
   [0xD800; 0xDBFF] and *low* must be in the range [0xDC00; 0xDFFF].


Creating and accessing Unicode strings
--------------------------------------

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

PyObject *PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)
    *Return value: New reference.*

   Create a new Unicode object.  *maxchar* should be the true maximum
   code point to be placed in the string.  As an approximation, it can
   be rounded up to the nearest value in the sequence 127, 255, 65535,
   1114111.

   This is the recommended way to allocate a new Unicode object.
   Objects created using this function are not resizable.

   New in version 3.3.

PyObject *PyUnicode_FromKindAndData(int kind, const void *buffer, Py_ssize_t size)
    *Return value: New reference.*

   Create a new Unicode object with the given *kind* (possible values
   are "PyUnicode_1BYTE_KIND" etc., as returned by
   "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 ("PyUnicode_4BYTE_KIND") and it consists only of codepoints
   in the UCS1 range, it will be transformed into UCS1
   ("PyUnicode_1BYTE_KIND").

   New in version 3.3.

PyObject *PyUnicode_FromStringAndSize(const char *u, Py_ssize_t size)
    *Return value: New reference.** Part of the Stable ABI.*

   Create a Unicode object from the char buffer *u*.  The bytes will
   be interpreted as being UTF-8 encoded.  The buffer is copied into
   the new object. The return value might be a shared object, i.e.
   modification of the data is not allowed.

   This function raises "SystemError" when:

   * *size* < 0,

   * *u* is "NULL" and *size* > 0

   Changed in version 3.12: *u* == "NULL" with *size* > 0 is not
   allowed anymore.

PyObject *PyUnicode_FromString(const char *u)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyUnicode_FromFormat(const char *format, ...)
    *Return value: New reference.** Part of the Stable ABI.*

   Take a C "printf()"-style *format* string and a variable number of
   arguments, calculate the size of the resulting Python Unicode
   string and return a string with the values formatted into it.  The
   variable arguments must be C types and must correspond exactly to
   the format characters in the *format* ASCII-encoded string. The
   following format characters are allowed:

   +---------------------+-----------------------+------------------------------------+
   | Format Characters   | Type                  | Comment                            |
   |=====================|=======================|====================================|
   | "%%"                | *n/a*                 | The literal % character.           |
   +---------------------+-----------------------+------------------------------------+
   | "%c"                | int                   | A single character, represented as |
   |                     |                       | a C int.                           |
   +---------------------+-----------------------+------------------------------------+
   | "%d"                | int                   | Equivalent to "printf("%d")". [1]  |
   +---------------------+-----------------------+------------------------------------+
   | "%u"                | unsigned int          | Equivalent to "printf("%u")". [1]  |
   +---------------------+-----------------------+------------------------------------+
   | "%ld"               | long                  | Equivalent to "printf("%ld")". [1] |
   +---------------------+-----------------------+------------------------------------+
   | "%li"               | long                  | Equivalent to "printf("%li")". [1] |
   +---------------------+-----------------------+------------------------------------+
   | "%lu"               | unsigned long         | Equivalent to "printf("%lu")". [1] |
   +---------------------+-----------------------+------------------------------------+
   | "%lld"              | long long             | Equivalent to "printf("%lld")".    |
   |                     |                       | [1]                                |
   +---------------------+-----------------------+------------------------------------+
   | "%lli"              | long long             | Equivalent to "printf("%lli")".    |
   |                     |                       | [1]                                |
   +---------------------+-----------------------+------------------------------------+
   | "%llu"              | unsigned long long    | Equivalent to "printf("%llu")".    |
   |                     |                       | [1]                                |
   +---------------------+-----------------------+------------------------------------+
   | "%zd"               | "Py_ssize_t"          | Equivalent to "printf("%zd")". [1] |
   +---------------------+-----------------------+------------------------------------+
   | "%zi"               | "Py_ssize_t"          | Equivalent to "printf("%zi")". [1] |
   +---------------------+-----------------------+------------------------------------+
   | "%zu"               | size_t                | Equivalent to "printf("%zu")". [1] |
   +---------------------+-----------------------+------------------------------------+
   | "%i"                | int                   | Equivalent to "printf("%i")". [1]  |
   +---------------------+-----------------------+------------------------------------+
   | "%x"                | int                   | Equivalent to "printf("%x")". [1]  |
   +---------------------+-----------------------+------------------------------------+
   | "%s"                | const char*           | A null-terminated C character      |
   |                     |                       | array.                             |
   +---------------------+-----------------------+------------------------------------+
   | "%p"                | const void*           | The hex representation of a C      |
   |                     |                       | pointer. Mostly equivalent to      |
   |                     |                       | "printf("%p")" except that it is   |
   |                     |                       | guaranteed to start with the       |
   |                     |                       | literal "0x" regardless of what    |
   |                     |                       | the platform's "printf" yields.    |
   +---------------------+-----------------------+------------------------------------+
   | "%A"                | PyObject*             | The result of calling "ascii()".   |
   +---------------------+-----------------------+------------------------------------+
   | "%U"                | PyObject*             | A Unicode object.                  |
   +---------------------+-----------------------+------------------------------------+
   | "%V"                | PyObject*, const      | A Unicode object (which may be     |
   |                     | char*                 | "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()".                 |
   +---------------------+-----------------------+------------------------------------+

   Note:

     The width formatter unit is number of characters rather than
     bytes. The precision formatter unit is number of bytes 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").

   [1] For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd,
       zi, zu, i, x): the 0-conversion flag has effect even when a
       precision is given.

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

   Changed in version 3.3: Support for ""%li"", ""%lli"" and ""%zi""
   added.

   Changed in version 3.4: Support width and precision formatter for
   ""%s"", ""%A"", ""%U"", ""%V"", ""%S"", ""%R"" added.

   Changed in version 3.12: An unrecognized format character now sets
   a "SystemError". In previous versions it caused all the rest of the
   format string to be copied as-is to the result string, and any
   extra arguments discarded.

PyObject *PyUnicode_FromFormatV(const char *format, va_list vargs)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

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

   "bytes", "bytearray" and other *bytes-like objects* are decoded
   according to the given *encoding* and using the error handling
   defined by *errors*. Both can be "NULL" to have the interface use
   the default values (see Built-in Codecs for details).

   All other objects, including Unicode objects, cause a "TypeError"
   to be set.

   The API returns "NULL" if there was an error.  The caller is
   responsible for decref'ing the returned objects.

Py_ssize_t PyUnicode_GetLength(PyObject *unicode)
    * Part of the Stable ABI since version 3.7.*

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

   New in version 3.3.

Py_ssize_t PyUnicode_CopyCharacters(PyObject *to, Py_ssize_t to_start, PyObject *from, Py_ssize_t from_start, Py_ssize_t how_many)

   Copy characters from one Unicode object into another.  This
   function performs character conversion when necessary and falls
   back to "memcpy()" if possible.  Returns "-1" and sets an exception
   on error, otherwise returns the number of copied characters.

   New in version 3.3.

Py_ssize_t PyUnicode_Fill(PyObject *unicode, Py_ssize_t start, Py_ssize_t length, Py_UCS4 fill_char)

   Fill a string with a character: write *fill_char* into
   "unicode[start:start+length]".

   Fail if *fill_char* is bigger than the string maximum character, or
   if the string has more than 1 reference.

   Return the number of written character, or return "-1" and raise an
   exception on error.

   New in version 3.3.

int PyUnicode_WriteChar(PyObject *unicode, Py_ssize_t index, Py_UCS4 character)
    * Part of the Stable ABI since version 3.7.*

   Write a character to a string.  The string must have been created
   through "PyUnicode_New()".  Since Unicode strings are supposed to
   be immutable, the string must not be shared, or have been hashed
   yet.

   This function checks that *unicode* is a Unicode object, that the
   index is not out of bounds, and that the object can be modified
   safely (i.e. that it its reference count is one).

   New in version 3.3.

Py_UCS4 PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)
    * Part of the Stable ABI since version 3.7.*

   Read a character from a string.  This function checks that
   *unicode* is a Unicode object and the index is not out of bounds,
   in contrast to "PyUnicode_READ_CHAR()", which performs no error
   checking.

   New in version 3.3.

PyObject *PyUnicode_Substring(PyObject *str, Py_ssize_t start, Py_ssize_t end)
    *Return value: New reference.** Part of the Stable ABI since
   version 3.7.*

   Return a substring of *str*, from character index *start*
   (included) to character index *end* (excluded).  Negative indices
   are not supported.

   New in version 3.3.

Py_UCS4 *PyUnicode_AsUCS4(PyObject *u, Py_UCS4 *buffer, Py_ssize_t buflen, int copy_null)
    * Part of the Stable ABI since version 3.7.*

   Copy the string *u* into a UCS4 buffer, including a null character,
   if *copy_null* is set.  Returns "NULL" and sets an exception on
   error (in particular, a "SystemError" if *buflen* is smaller than
   the length of *u*).  *buffer* is returned on success.

   New in version 3.3.

Py_UCS4 *PyUnicode_AsUCS4Copy(PyObject *u)
    * Part of the Stable ABI since version 3.7.*

   Copy the string *u* into a new UCS4 buffer that is allocated using
   "PyMem_Malloc()".  If this fails, "NULL" is returned with a
   "MemoryError" set.  The returned buffer always has an extra null
   code point appended.

   New in version 3.3.

PyObject *PyUnicode_FromObject(PyObject *obj)
    *Return value: New reference.** Part of the Stable ABI.*

   Copy an instance of a Unicode subtype to a new true Unicode object
   if necessary. If *obj* is already a true Unicode object (not a
   subtype), return the reference with incremented refcount.

   Objects other than Unicode or its subtypes will cause a
   "TypeError".


Locale Encoding
---------------

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

PyObject *PyUnicode_DecodeLocaleAndSize(const char *str, Py_ssize_t len, const char *errors)
    *Return value: New reference.** Part of the Stable ABI since
   version 3.7.*

   Decode a string from UTF-8 on Android and VxWorks, or from the
   current locale encoding on other platforms. The supported error
   handlers are ""strict"" and ""surrogateescape"" (**PEP 383**). The
   decoder uses ""strict"" error handler if *errors* is "NULL".  *str*
   must end with a null character but cannot contain embedded null
   characters.

   Use "PyUnicode_DecodeFSDefaultAndSize()" to decode a string from
   the *filesystem encoding and error handler*.

   This function ignores the Python UTF-8 Mode.

   See also: The "Py_DecodeLocale()" function.

   New in version 3.3.

   Changed in version 3.7: The function now also uses the current
   locale encoding for the "surrogateescape" error handler, except on
   Android. Previously, "Py_DecodeLocale()" was used for the
   "surrogateescape", and the current locale encoding was used for
   "strict".

PyObject *PyUnicode_DecodeLocale(const char *str, const char *errors)
    *Return value: New reference.** Part of the Stable ABI since
   version 3.7.*

   Similar to "PyUnicode_DecodeLocaleAndSize()", but compute the
   string length using "strlen()".

   New in version 3.3.

PyObject *PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)
    *Return value: New reference.** Part of the Stable ABI since
   version 3.7.*

   Encode a Unicode object to UTF-8 on Android and VxWorks, or to the
   current locale encoding on other platforms. The supported error
   handlers are ""strict"" and ""surrogateescape"" (**PEP 383**). The
   encoder uses ""strict"" error handler if *errors* is "NULL". Return
   a "bytes" object. *unicode* cannot contain embedded null
   characters.

   Use "PyUnicode_EncodeFSDefault()" to encode a string to the
   *filesystem encoding and error handler*.

   This function ignores the Python UTF-8 Mode.

   See also: The "Py_EncodeLocale()" function.

   New in version 3.3.

   Changed in version 3.7: The function now also uses the current
   locale encoding for the "surrogateescape" error handler, except on
   Android. Previously, "Py_EncodeLocale()" was used for the
   "surrogateescape", and the current locale encoding was used for
   "strict".


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

Functions encoding to and decoding from the *filesystem encoding and
error handler* (**PEP 383** and **PEP 529**).

To encode file names to "bytes" during argument parsing, the ""O&""
converter should be used, passing "PyUnicode_FSConverter()" as the
conversion function:

int PyUnicode_FSConverter(PyObject *obj, void *result)
    * Part of the Stable ABI.*

   ParseTuple converter: encode "str" objects -- obtained directly or
   through the "os.PathLike" interface -- 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.

   Changed in version 3.6: Accepts a *path-like object*.

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

int PyUnicode_FSDecoder(PyObject *obj, void *result)
    * Part of the Stable ABI.*

   ParseTuple converter: decode "bytes" objects -- obtained either
   directly or indirectly through the "os.PathLike" interface -- 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.

   Changed in version 3.6: Accepts a *path-like object*.

PyObject *PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
    *Return value: New reference.** Part of the Stable ABI.*

   Decode a string from the *filesystem encoding and error handler*.

   If you need to decode a string from the current locale encoding,
   use "PyUnicode_DecodeLocaleAndSize()".

   See also: The "Py_DecodeLocale()" function.

   Changed in version 3.6: The *filesystem error handler* is now used.

PyObject *PyUnicode_DecodeFSDefault(const char *s)
    *Return value: New reference.** Part of the Stable ABI.*

   Decode a null-terminated string from the *filesystem encoding and
   error handler*.

   If the string length is known, use
   "PyUnicode_DecodeFSDefaultAndSize()".

   Changed in version 3.6: The *filesystem error handler* is now used.

PyObject *PyUnicode_EncodeFSDefault(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Encode a Unicode object to the *filesystem encoding and error
   handler*, and return "bytes". Note that the resulting "bytes"
   object can contain null bytes.

   If you need to encode a string to the current locale encoding, use
   "PyUnicode_EncodeLocale()".

   See also: The "Py_EncodeLocale()" function.

   New in version 3.2.

   Changed in version 3.6: The *filesystem error handler* is now used.


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

wchar_t support for platforms which support it:

PyObject *PyUnicode_FromWideChar(const wchar_t *w, Py_ssize_t size)
    *Return value: New reference.** Part of the Stable ABI.*

   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(PyObject *unicode, wchar_t *w, Py_ssize_t size)
    * Part of the Stable ABI.*

   Copy the Unicode object contents into the wchar_t buffer *w*.  At
   most *size* wchar_t characters are copied (excluding a possibly
   trailing null 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 null-terminated.  It is
   the responsibility of the caller to make sure that the wchar_t*
   string is null-terminated in case this is required by the
   application. Also, note that the wchar_t* string might contain null
   characters, which would cause the string to be truncated when used
   with most C functions.

wchar_t *PyUnicode_AsWideCharString(PyObject *unicode, Py_ssize_t *size)
    * Part of the Stable ABI since version 3.7.*

   Convert the Unicode object to a wide character string. The output
   string always ends with a null character. If *size* is not "NULL",
   write the number of wide characters (excluding the trailing null
   termination character) into **size*. Note that the resulting
   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 wchar_t* string contains null characters a
   "ValueError" is raised.

   Returns a buffer allocated by "PyMem_New()" (use "PyMem_Free()" to
   free it) on success. On error, returns "NULL" and **size* is
   undefined. Raises a "MemoryError" if memory allocation is failed.

   New in version 3.2.

   Changed in version 3.7: Raises a "ValueError" if *size* is "NULL"
   and the wchar_t* string contains null characters.


Built-in Codecs
===============

Python provides a set of built-in codecs which are written in C for
speed. All of these codecs are directly usable via the following
functions.

Many of the following APIs take two arguments encoding and errors, and
they have the same semantics as the ones of the built-in "str()"
string object constructor.

Setting encoding to "NULL" causes the default encoding to be used
which is UTF-8.  The file system calls should use
"PyUnicode_FSConverter()" for encoding file names. This uses the
*filesystem encoding and error handler* internally.

Error handling is set by errors which may also be set to "NULL"
meaning to use the default handling defined for the codec.  Default
error handling for all built-in codecs is "strict" ("ValueError" is
raised).

The codecs all use a similar interface.  Only deviations from the
following generic ones are documented for simplicity.


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

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.** Part of the Stable ABI.*

   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 "str()" 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_AsEncodedString(PyObject *unicode, const char *encoding, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

   Encode a Unicode object and return the result as Python bytes
   object. *encoding* and *errors* have the same meaning as the
   parameters of the same name in the Unicode "encode()" method. The
   codec to be used is looked up using the Python codec registry.
   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.** Part of the Stable ABI.*

   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.** Part of the Stable ABI.*

   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_AsUTF8String(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Encode a Unicode object using UTF-8 and return the result as Python
   bytes object.  Error handling is "strict".  Return "NULL" if an
   exception was raised by the codec.

const char *PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *size)
    * Part of the Stable ABI since version 3.10.*

   Return a pointer to the UTF-8 encoding of the Unicode object, and
   store the size of the encoded representation (in bytes) in *size*.
   The *size* argument can be "NULL"; in this case no size will be
   stored.  The returned buffer always has an extra null byte appended
   (not included in *size*), regardless of whether there are any other
   null code points.

   In the case of an error, "NULL" is returned with an exception set
   and no *size* is stored.

   This caches the UTF-8 representation of the string in the Unicode
   object, and subsequent calls will return a pointer to the same
   buffer.  The caller is not responsible for deallocating the buffer.
   The buffer is deallocated and pointers to it become invalid when
   the Unicode object is garbage collected.

   New in version 3.3.

   Changed in version 3.7: The return type is now "const char *"
   rather of "char *".

   Changed in version 3.10: This function is a part of the limited
   API.

const char *PyUnicode_AsUTF8(PyObject *unicode)

   As "PyUnicode_AsUTF8AndSize()", but does not store the size.

   New in version 3.3.

   Changed in version 3.7: The return type is now "const char *"
   rather of "char *".


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)
    *Return value: New reference.** Part of the Stable ABI.*

   Decode *size* bytes from a UTF-32 encoded buffer string and return
   the corresponding Unicode object.  *errors* (if non-"NULL") defines
   the error handling. It defaults to "strict".

   If *byteorder* is non-"NULL", the decoder starts decoding using the
   given byte order:

      *byteorder == -1: little endian
      *byteorder == 0:  native order
      *byteorder == 1:  big endian

   If "*byteorder" is zero, and the first four bytes of the input data
   are a byte order mark (BOM), the decoder switches to this byte
   order and the BOM is not copied into the resulting Unicode string.
   If "*byteorder" is "-1" 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.

   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)
    *Return value: New reference.** Part of the Stable ABI.*

   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_AsUTF32String(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Return a Python byte string using the UTF-32 encoding in native
   byte order. The string always starts with a BOM mark.  Error
   handling is "strict". Return "NULL" if an exception was raised by
   the codec.


UTF-16 Codecs
-------------

These are the UTF-16 codec APIs:

PyObject *PyUnicode_DecodeUTF16(const char *s, Py_ssize_t size, const char *errors, int *byteorder)
    *Return value: New reference.** Part of the Stable ABI.*

   Decode *size* bytes from a UTF-16 encoded buffer string and return
   the corresponding Unicode object.  *errors* (if non-"NULL") defines
   the error handling. It defaults to "strict".

   If *byteorder* is non-"NULL", the decoder starts decoding using the
   given byte order:

      *byteorder == -1: little endian
      *byteorder == 0:  native order
      *byteorder == 1:  big endian

   If "*byteorder" is zero, and the first two bytes of the input data
   are a byte order mark (BOM), the decoder switches to this byte
   order and the BOM is not copied into the resulting Unicode string.
   If "*byteorder" is "-1" 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.** Part of the Stable ABI.*

   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_AsUTF16String(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Return a Python byte string using the UTF-16 encoding in native
   byte order. The string always starts with a BOM mark.  Error
   handling is "strict". Return "NULL" if an exception was raised by
   the codec.


UTF-7 Codecs
------------

These are the UTF-7 codec APIs:

PyObject *PyUnicode_DecodeUTF7(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

   Create a Unicode object by decoding *size* bytes of the UTF-7
   encoded string *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)
    *Return value: New reference.** Part of the Stable ABI.*

   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*.


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.** Part of the Stable ABI.*

   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_AsUnicodeEscapeString(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Encode a Unicode object using Unicode-Escape and return the result
   as a bytes object.  Error handling is "strict".  Return "NULL" if
   an exception was raised by the codec.


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

These are the "Raw Unicode Escape" codec APIs:

PyObject *PyUnicode_DecodeRawUnicodeEscape(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Encode a Unicode object using Raw-Unicode-Escape and return the
   result as a bytes object.  Error handling is "strict".  Return
   "NULL" if an exception was raised by the codec.


Latin-1 Codecs
--------------

These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256
Unicode ordinals and only these are accepted by the codecs during
encoding.

PyObject *PyUnicode_DecodeLatin1(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyUnicode_AsLatin1String(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

   Encode a Unicode object using Latin-1 and return the result as
   Python bytes object.  Error handling is "strict".  Return "NULL" if
   an exception was raised by the codec.


ASCII Codecs
------------

These are the ASCII codec APIs.  Only 7-bit ASCII data is accepted.
All other codes generate errors.

PyObject *PyUnicode_DecodeASCII(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyUnicode_AsASCIIString(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI.*

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


Character Map Codecs
--------------------

This codec is special in that it can be used to implement many
different codecs (and this is in fact what was done to obtain most of
the standard codecs included in the "encodings" package). The codec
uses mappings to encode and decode characters.  The mapping objects
provided must support the "__getitem__()" mapping interface;
dictionaries and sequences work well.

These are the mapping codec APIs:

PyObject *PyUnicode_DecodeCharmap(const char *data, Py_ssize_t size, PyObject *mapping, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

   Create a Unicode object by decoding *size* bytes of the encoded
   string *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 applied.  Else
   *mapping* must map bytes ordinals (integers in the range from 0 to
   255) to Unicode strings, integers (which are then interpreted as
   Unicode ordinals) or "None".  Unmapped data bytes -- ones which
   cause a "LookupError", as well as ones which get mapped to "None",
   "0xFFFE" or "'\ufffe'", are treated as undefined mappings and cause
   an error.

PyObject *PyUnicode_AsCharmapString(PyObject *unicode, PyObject *mapping)
    *Return value: New reference.** Part of the Stable ABI.*

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

   The *mapping* object must map Unicode ordinal integers to bytes
   objects, integers in the range from 0 to 255 or "None".  Unmapped
   character ordinals (ones which cause a "LookupError") as well as
   mapped to "None" are treated as "undefined mapping" and cause an
   error.

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

PyObject *PyUnicode_Translate(PyObject *str, PyObject *table, const char *errors)
    *Return value: New reference.** Part of the Stable ABI.*

   Translate a string by applying a character mapping table to it and
   return the resulting Unicode object. Return "NULL" if an exception
   was raised by the codec.

   The mapping table must map Unicode ordinal integers to Unicode
   ordinal integers or "None" (causing deletion of the character).

   Mapping tables need only provide the "__getitem__()" interface;
   dictionaries and sequences work well.  Unmapped character ordinals
   (ones which cause 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.


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.** Part of the Stable ABI on Windows
   since version 3.7.*

   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, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)
    *Return value: New reference.** Part of the Stable ABI on Windows
   since version 3.7.*

   If *consumed* is "NULL", behave 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_AsMBCSString(PyObject *unicode)
    *Return value: New reference.** Part of the Stable ABI on Windows
   since version 3.7.*

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

PyObject *PyUnicode_EncodeCodePage(int code_page, PyObject *unicode, const char *errors)
    *Return value: New reference.** Part of the Stable ABI on Windows
   since version 3.7.*

   Encode the Unicode object using the specified code page and return
   a Python bytes object.  Return "NULL" if an exception was raised by
   the codec. Use "CP_ACP" code page to get the MBCS encoder.

   New in version 3.3.


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.** Part of the Stable ABI.*

   Concat two strings giving a new Unicode string.

PyObject *PyUnicode_Split(PyObject *s, PyObject *sep, Py_ssize_t maxsplit)
    *Return value: New reference.** Part of the Stable ABI.*

   Split a string giving a list of Unicode strings.  If *sep* is
   "NULL", splitting will be done at all whitespace substrings.
   Otherwise, splits occur at the given separator.  At most *maxsplit*
   splits will be done.  If negative, no limit is set.  Separators are
   not included in the resulting list.

PyObject *PyUnicode_Splitlines(PyObject *s, int keepend)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyUnicode_Join(PyObject *separator, PyObject *seq)
    *Return value: New reference.** Part of the Stable ABI.*

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

Py_ssize_t PyUnicode_Tailmatch(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)
    * Part of the Stable ABI.*

   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)
    * Part of the Stable ABI.*

   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_FindChar(PyObject *str, Py_UCS4 ch, Py_ssize_t start, Py_ssize_t end, int direction)
    * Part of the Stable ABI since version 3.7.*

   Return the first position of the character *ch* in "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.

   New in version 3.3.

   Changed in version 3.7: *start* and *end* are now adjusted to
   behave like "str[start:end]".

Py_ssize_t PyUnicode_Count(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end)
    * Part of the Stable ABI.*

   Return the number of non-overlapping occurrences of *substr* in
   "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.** Part of the Stable ABI.*

   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)
    * Part of the Stable ABI.*

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

   This function returns "-1" upon failure, so one should call
   "PyErr_Occurred()" to check for errors.

int PyUnicode_CompareWithASCIIString(PyObject *uni, const char *string)
    * Part of the Stable ABI.*

   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.

   This function does not raise exceptions.

PyObject *PyUnicode_RichCompare(PyObject *left, PyObject *right, int op)
    *Return value: New reference.** Part of the Stable ABI.*

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

   * "NULL" in case an exception was raised

   * "Py_True" or "Py_False" for successful comparisons

   * "Py_NotImplemented" in case the type combination is unknown

   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.** Part of the Stable ABI.*

   Return a new string object from *format* and *args*; this is
   analogous to "format % args".

int PyUnicode_Contains(PyObject *container, PyObject *element)
    * Part of the Stable ABI.*

   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)
    * Part of the Stable ABI.*

   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)
    *Return value: New reference.** Part of the Stable ABI.*

   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.
