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).
Py_UNICODE* and UTF-8 representations are created on demand and cached
in the Unicode object. The Py_UNICODE* representation is deprecated
and inefficient; it should be avoided in performance- or memory-sensitive
situations.
Due to the transition between the old APIs and the new APIs, unicode objects
can internally be in two states depending on how they were created:
- “canonical” unicode objects are all objects created by a non-deprecated
unicode API. They use the most efficient representation allowed by the
implementation.
- “legacy” unicode objects have been created through one of the deprecated
APIs (typically
PyUnicode_FromUnicode()) and only bear the
Py_UNICODE* representation; you will have to call
PyUnicode_READY() on them before calling any other API.
Unicode Type
These are the basic Unicode object types used for the Unicode implementation in
Python:
-
Py_UCS4
-
Py_UCS2
-
Py_UCS1
These types are typedefs for unsigned integer types wide enough to contain
characters of 32 bits, 16 bits and 8 bits, respectively. When dealing with
single Unicode characters, use Py_UCS4.
-
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.
-
PyASCIIObject
-
PyCompactUnicodeObject
-
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.
-
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.
-
int
PyUnicode_READY(PyObject *o)
Ensure the string object o is in the “canonical” representation. This is
required before using any of the access macros described below.
Returns 0 on success and -1 with an exception set on failure, which in
particular happens if memory allocation fails.
-
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).
-
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 macro. Make sure
PyUnicode_READY() has been called before accessing this.
-
PyUnicode_WCHAR_KIND
-
PyUnicode_1BYTE_KIND
-
PyUnicode_2BYTE_KIND
-
PyUnicode_4BYTE_KIND
Return values of the PyUnicode_KIND() macro.
-
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).
-
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).
-
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 macro does not do any sanity checks and is
intended for usage in loops. The caller should cache the kind value and
data pointer as obtained from other macro 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.
-
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.
-
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.
-
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.
-
int
PyUnicode_ClearFreeList()
Clear the free list. Return the total number of freed items.
-
Py_ssize_t
PyUnicode_GET_SIZE(PyObject *o)
Return the size of the deprecated Py_UNICODE representation, in
code units (this includes surrogate pairs as 2 units). o has to be a
Unicode object (not checked).
Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Unicode API, please migrate to using
PyUnicode_GET_LENGTH().
-
Py_ssize_t
PyUnicode_GET_DATA_SIZE(PyObject *o)
Return the size of the deprecated Py_UNICODE representation in
bytes. o has to be a Unicode object (not checked).
Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Unicode API, please migrate to using
PyUnicode_GET_LENGTH().
-
Py_UNICODE*
PyUnicode_AS_UNICODE(PyObject *o)
-
const char*
PyUnicode_AS_DATA(PyObject *o)
Return a pointer to a Py_UNICODE representation of the object. The
returned buffer is always terminated with an extra null code point. It
may also contain embedded null code points, which would cause the string
to be truncated when used in most C functions. The AS_DATA form
casts the pointer to const char *. The o argument has to be
a Unicode object (not checked).
Changed in version 3.3: This macro is now inefficient – because in many cases the
Py_UNICODE representation does not exist and needs to be created
– and can fail (return NULL with an exception set). Try to port the
code to use the new PyUnicode_nBYTE_DATA() macros or use
PyUnicode_WRITE() or PyUnicode_READ().
Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Unicode API, please migrate to using the
PyUnicode_nBYTE_DATA() family of macros.
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.
Deprecated since version 3.3: This function uses simple case mappings.
-
Py_UNICODE
Py_UNICODE_TOUPPER(Py_UNICODE ch)
Return the character ch converted to upper case.
Deprecated since version 3.3: This function uses simple case mappings.
-
Py_UNICODE
Py_UNICODE_TOTITLE(Py_UNICODE 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_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.
These APIs can be used to work with surrogates:
-
Py_UNICODE_IS_SURROGATE(ch)
Check if ch is a surrogate (0xD800 <= ch <= 0xDFFF).
-
Py_UNICODE_IS_HIGH_SURROGATE(ch)
Check if ch is a high surrogate (0xD800 <= ch <= 0xDBFF).
-
Py_UNICODE_IS_LOW_SURROGATE(ch)
Check if ch is a low surrogate (0xDC00 <= ch <= 0xDFFF).
-
Py_UNICODE_JOIN_SURROGATES(high, 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.
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)
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.
-
PyObject*
PyUnicode_FromKindAndData(int kind, const void *buffer, Py_ssize_t size)
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.
-
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. The buffer is copied into the new
object. If the buffer is not NULL, the return value might be a shared
object, i.e. modification of the data is not allowed.
If u is NULL, this function behaves like PyUnicode_FromUnicode()
with the buffer set to NULL. This usage is deprecated in favor of
PyUnicode_New().
-
PyObject *
PyUnicode_FromString(const char *u)
Create a Unicode object from a UTF-8 encoded null-terminated char buffer
u.
-
PyObject*
PyUnicode_FromFormat(const char *format, ...)
Take a C printf()-style format string and a variable number of
arguments, calculate the size of the resulting Python unicode string and return
a string with the values formatted into it. The variable arguments must be C
types and must correspond exactly to the format characters in the format
ASCII-encoded string. The following format characters are allowed:
| Format Characters |
Type |
Comment |
%% |
n/a |
The literal % character. |
%c |
int |
A single character,
represented as a C int. |
%d |
int |
Exactly equivalent to
printf("%d"). |
%u |
unsigned int |
Exactly equivalent to
printf("%u"). |
%ld |
long |
Exactly equivalent to
printf("%ld"). |
%li |
long |
Exactly equivalent to
printf("%li"). |
%lu |
unsigned long |
Exactly equivalent to
printf("%lu"). |
%lld |
long long |
Exactly equivalent to
printf("%lld"). |
%lli |
long long |
Exactly equivalent to
printf("%lli"). |
%llu |
unsigned long long |
Exactly equivalent to
printf("%llu"). |
%zd |
Py_ssize_t |
Exactly equivalent to
printf("%zd"). |
%zi |
Py_ssize_t |
Exactly equivalent to
printf("%zi"). |
%zu |
size_t |
Exactly equivalent to
printf("%zu"). |
%i |
int |
Exactly equivalent to
printf("%i"). |
%x |
int |
Exactly equivalent to
printf("%x"). |
%s |
char* |
A null-terminated C character
array. |
%p |
void* |
The hex representation of a C
pointer. Mostly equivalent to
printf("%p") except that
it is guaranteed to start with
the literal 0x regardless
of what the platform’s
printf yields. |
%A |
PyObject* |
The result of calling
ascii(). |
%U |
PyObject* |
A unicode object. |
%V |
PyObject*, char * |
A unicode object (which may be
NULL) and a null-terminated
C character array as a second
parameter (which will be used,
if the first parameter is
NULL). |
%S |
PyObject* |
The result of calling
PyObject_Str(). |
%R |
PyObject* |
The result of calling
PyObject_Repr(). |
An unrecognized format character causes all the rest of the format string to be
copied as-is to the result string, and any extra arguments discarded.
Note
The 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).
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.
-
PyObject*
PyUnicode_FromFormatV(const char *format, va_list vargs)
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.
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)
Return the length of the Unicode object, in code points.
-
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.
-
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.
-
int
PyUnicode_WriteChar(PyObject *unicode, Py_ssize_t index, Py_UCS4 character)
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).
-
Py_UCS4
PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)
Read a character from a string. This function checks that unicode is a
Unicode object and the index is not out of bounds, in contrast to the macro
version PyUnicode_READ_CHAR().
-
PyObject*
PyUnicode_Substring(PyObject *str, Py_ssize_t start, Py_ssize_t end)
Return a substring of str, from character index start (included) to
character index end (excluded). Negative indices are not supported.
-
Py_UCS4*
PyUnicode_AsUCS4(PyObject *u, Py_UCS4 *buffer, Py_ssize_t buflen, int copy_null)
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.
-
Py_UCS4*
PyUnicode_AsUCS4Copy(PyObject *u)
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.
Deprecated Py_UNICODE APIs
Deprecated since version 3.3, will be removed in version 4.0.
These API functions are deprecated with the implementation of PEP 393.
Extension modules can continue using them, as they will not be removed in Python
3.x, but need to be aware that their use can now cause performance and memory hits.
-
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.
If the buffer is NULL, PyUnicode_READY() must be called once the
string content has been filled before using any of the access macros such as
PyUnicode_KIND().
Please migrate to using PyUnicode_FromKindAndData(),
PyUnicode_FromWideChar() or PyUnicode_New().
-
Py_UNICODE*
PyUnicode_AsUnicode(PyObject *unicode)
Return a read-only pointer to the Unicode object’s internal
Py_UNICODE buffer, or NULL on error. This will create the
Py_UNICODE* representation of the object if it is not yet
available. The buffer is always terminated with an extra null code point.
Note that the resulting Py_UNICODE string may also contain
embedded null code points, which would cause the string to be truncated when
used in most C functions.
Please migrate to using PyUnicode_AsUCS4(),
PyUnicode_AsWideChar(), PyUnicode_ReadChar() or similar new
APIs.
-
PyObject*
PyUnicode_TransformDecimalToASCII(Py_UNICODE *s, Py_ssize_t size)
Create a Unicode object by replacing all decimal digits in
Py_UNICODE buffer of the given size by ASCII digits 0–9
according to their decimal value. Return NULL if an exception occurs.
-
Py_UNICODE*
PyUnicode_AsUnicodeAndSize(PyObject *unicode, Py_ssize_t *size)
Like PyUnicode_AsUnicode(), but also saves the Py_UNICODE()
array length (excluding the extra null terminator) in size.
Note that the resulting Py_UNICODE* string
may contain embedded null code points, which would cause the string to be
truncated when used in most C functions.
-
Py_UNICODE*
PyUnicode_AsUnicodeCopy(PyObject *unicode)
Create a copy of a Unicode string ending with a null code point. Return NULL
and raise a MemoryError exception on memory allocation failure,
otherwise return a new allocated buffer (use PyMem_Free() to free
the buffer). Note that the resulting Py_UNICODE* string may
contain embedded null code points, which would cause the string to be
truncated when used in most C functions.
Please migrate to using PyUnicode_AsUCS4Copy() or similar new APIs.
-
Py_ssize_t
PyUnicode_GetSize(PyObject *unicode)
Return the size of the deprecated Py_UNICODE representation, in
code units (this includes surrogate pairs as 2 units).
Please migrate to using PyUnicode_GetLength().
-
PyObject*
PyUnicode_FromObject(PyObject *obj)
- Return value: New reference.
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)
Decode a string from the current locale encoding. 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
Py_FileSystemDefaultEncoding (the locale encoding read at
Python startup).
Changed in version 3.6.5: The function now also uses the current locale encoding for the
surrogateescape error handler. 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)
Similar to PyUnicode_DecodeLocaleAndSize(), but compute the string
length using strlen().
-
PyObject*
PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)
Encode a Unicode object to the current locale encoding. 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
Py_FileSystemDefaultEncoding (the locale encoding read at
Python startup).
Changed in version 3.6.5: The function now also uses the current locale encoding for the
surrogateescape error handler. Previously, Py_EncodeLocale()
was used for the surrogateescape, and the current locale encoding was
used for strict.
File System Encoding
To encode and decode file names and other environment strings,
Py_FileSystemDefaultEncoding should be used as the encoding, and
Py_FileSystemDefaultEncodeErrors should be used as the 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)
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.
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)
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.
-
PyObject*
PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
Decode a string using Py_FileSystemDefaultEncoding and the
Py_FileSystemDefaultEncodeErrors error handler.
If Py_FileSystemDefaultEncoding is not set, fall back to the
locale encoding.
Py_FileSystemDefaultEncoding is initialized at startup from the
locale encoding and cannot be modified later. If you need to decode a string
from the current locale encoding, use
PyUnicode_DecodeLocaleAndSize().
Changed in version 3.6: Use Py_FileSystemDefaultEncodeErrors error handler.
-
PyObject*
PyUnicode_DecodeFSDefault(const char *s)
Decode a null-terminated string using Py_FileSystemDefaultEncoding
and the Py_FileSystemDefaultEncodeErrors error handler.
If Py_FileSystemDefaultEncoding is not set, fall back to the
locale encoding.
Use PyUnicode_DecodeFSDefaultAndSize() if you know the string length.
Changed in version 3.6: Use Py_FileSystemDefaultEncodeErrors error handler.
-
PyObject*
PyUnicode_EncodeFSDefault(PyObject *unicode)
Encode a Unicode object to Py_FileSystemDefaultEncoding with the
Py_FileSystemDefaultEncodeErrors error handler, and return
bytes. Note that the resulting bytes object may contain
null bytes.
If Py_FileSystemDefaultEncoding is not set, fall back to the
locale encoding.
Py_FileSystemDefaultEncoding is initialized at startup from the
locale encoding and cannot be modified later. If you need to encode a string
to the current locale encoding, use PyUnicode_EncodeLocale().
Changed in version 3.6: Use Py_FileSystemDefaultEncodeErrors error handler.
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
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)
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.
Returns a buffer allocated by PyMem_Alloc() (use
PyMem_Free() to free it) on success. On error, returns NULL,
*size is undefined and raises a MemoryError. 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.
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 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.
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.
-
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.
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_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.
-
char*
PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *size)
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.
-
char*
PyUnicode_AsUTF8(PyObject *unicode)
As PyUnicode_AsUTF8AndSize(), but does not store the size.
-
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.
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.
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_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.
-
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 code point.
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_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.
-
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 a UCS-2 character.
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_AsUnicodeEscapeString(PyObject *unicode)
- Return value: New reference.
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.
-
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 bytes object. 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_AsRawUnicodeEscapeString(PyObject *unicode)
- Return value: New reference.
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.
-
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 bytes object. 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_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.
-
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.
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_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.
-
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.
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. 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.
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.
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.
-
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 the result as a bytes object. Return NULL if
an exception was raised by the codec.
The following codec API is special in that maps Unicode to Unicode.
-
PyObject*
PyUnicode_Translate(PyObject *unicode, PyObject *mapping, const char *errors)
- Return value: New reference.
Translate a Unicode object using the given mapping object and return the
resulting Unicode object. Return NULL if an exception was raised by the
codec.
The mapping object must map Unicode ordinal integers to Unicode strings,
integers (which are then interpreted as Unicode ordinals) or None
(causing deletion of the character). Unmapped character ordinals (ones
which cause a LookupError) are left untouched and are copied as-is.
-
PyObject*
PyUnicode_TranslateCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *mapping, 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.
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_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.
-
PyObject*
PyUnicode_EncodeCodePage(int code_page, PyObject *unicode, const char *errors)
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.
-
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.
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)
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.
-
Py_ssize_t
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_FindChar(PyObject *str, Py_UCS4 ch, Py_ssize_t start, Py_ssize_t end, int direction)
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.
-
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.
This function returns -1 upon failure, so one should call
PyErr_Occurred() to check for errors.
-
int
PyUnicode_CompareWithASCIIString(PyObject *uni, const char *string)
Compare a unicode object, uni, with string and return -1, 0, 1 for less
than, equal, and greater than, respectively. It is best to pass only
ASCII-encoded strings, but the function interprets the input string as
ISO-8859-1 if it contains non-ASCII characters.
This function does not raise exceptions.
-
PyObject*
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
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.
-
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.