mirror of https://github.com/python/cpython
246 lines
12 KiB
ReStructuredText
246 lines
12 KiB
ReStructuredText
.. highlightlang:: c
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.. _stringobjects:
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String Objects
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--------------
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These functions raise :exc:`TypeError` when expecting a string parameter and are
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called with a non-string parameter.
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.. index:: object: string
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.. ctype:: PyStringObject
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This subtype of :ctype:`PyObject` represents a Python string object.
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.. cvar:: PyTypeObject PyString_Type
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.. index:: single: StringType (in module types)
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This instance of :ctype:`PyTypeObject` represents the Python string type; it is
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the same object as ``str`` and ``types.StringType`` in the Python layer. .
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.. cfunction:: int PyString_Check(PyObject *o)
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Return true if the object *o* is a string object or an instance of a subtype of
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the string type.
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.. cfunction:: int PyString_CheckExact(PyObject *o)
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Return true if the object *o* is a string object, but not an instance of a
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subtype of the string type.
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.. cfunction:: PyObject* PyString_FromString(const char *v)
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Return a new string object with a copy of the string *v* as value on success,
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and *NULL* on failure. The parameter *v* must not be *NULL*; it will not be
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checked.
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.. cfunction:: PyObject* PyString_FromStringAndSize(const char *v, Py_ssize_t len)
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Return a new string object with a copy of the string *v* as value and length
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*len* on success, and *NULL* on failure. If *v* is *NULL*, the contents of the
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string are uninitialized.
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.. cfunction:: PyObject* PyString_FromFormat(const char *format, ...)
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Take a C :cfunc:`printf`\ -style *format* string and a variable number of
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arguments, calculate the size of the resulting Python string and return a string
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with the values formatted into it. The variable arguments must be C types and
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must correspond exactly to the format characters in the *format* string. The
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following format characters are allowed:
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.. % XXX: This should be exactly the same as the table in PyErr_Format.
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.. % One should just refer to the other.
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.. % XXX: The descriptions for %zd and %zu are wrong, but the truth is complicated
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.. % because not all compilers support the %z width modifier -- we fake it
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.. % when necessary via interpolating PY_FORMAT_SIZE_T.
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+-------------------+---------------+--------------------------------+
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| Format Characters | Type | Comment |
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+===================+===============+================================+
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| :attr:`%%` | *n/a* | The literal % character. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%c` | int | A single character, |
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| | | represented as an C int. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%d` | int | Exactly equivalent to |
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| | | ``printf("%d")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%u` | unsigned int | Exactly equivalent to |
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| | | ``printf("%u")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%ld` | long | Exactly equivalent to |
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| | | ``printf("%ld")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%lu` | unsigned long | Exactly equivalent to |
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| | | ``printf("%lu")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%zd` | Py_ssize_t | Exactly equivalent to |
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| | | ``printf("%zd")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%zu` | size_t | Exactly equivalent to |
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| | | ``printf("%zu")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%i` | int | Exactly equivalent to |
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| | | ``printf("%i")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%x` | int | Exactly equivalent to |
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| | | ``printf("%x")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%s` | char\* | A null-terminated C character |
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| | | array. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%p` | void\* | The hex representation of a C |
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| | | pointer. Mostly equivalent to |
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| | | ``printf("%p")`` except that |
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| | | it is guaranteed to start with |
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| | | the literal ``0x`` regardless |
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| | | of what the platform's |
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| | | ``printf`` yields. |
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+-------------------+---------------+--------------------------------+
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An unrecognized format character causes all the rest of the format string to be
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copied as-is to the result string, and any extra arguments discarded.
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.. cfunction:: PyObject* PyString_FromFormatV(const char *format, va_list vargs)
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Identical to :func:`PyString_FromFormat` except that it takes exactly two
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arguments.
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.. cfunction:: Py_ssize_t PyString_Size(PyObject *string)
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Return the length of the string in string object *string*.
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.. cfunction:: Py_ssize_t PyString_GET_SIZE(PyObject *string)
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Macro form of :cfunc:`PyString_Size` but without error checking.
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.. cfunction:: char* PyString_AsString(PyObject *string)
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Return a NUL-terminated representation of the contents of *string*. The pointer
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refers to the internal buffer of *string*, not a copy. The data must not be
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modified in any way, unless the string was just created using
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``PyString_FromStringAndSize(NULL, size)``. It must not be deallocated. If
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*string* is a Unicode object, this function computes the default encoding of
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*string* and operates on that. If *string* is not a string object at all,
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:cfunc:`PyString_AsString` returns *NULL* and raises :exc:`TypeError`.
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.. cfunction:: char* PyString_AS_STRING(PyObject *string)
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Macro form of :cfunc:`PyString_AsString` but without error checking. Only
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string objects are supported; no Unicode objects should be passed.
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.. cfunction:: int PyString_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)
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Return a NUL-terminated representation of the contents of the object *obj*
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through the output variables *buffer* and *length*.
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The function accepts both string and Unicode objects as input. For Unicode
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objects it returns the default encoded version of the object. If *length* is
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*NULL*, the resulting buffer may not contain NUL characters; if it does, the
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function returns ``-1`` and a :exc:`TypeError` is raised.
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The buffer refers to an internal string buffer of *obj*, not a copy. The data
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must not be modified in any way, unless the string was just created using
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``PyString_FromStringAndSize(NULL, size)``. It must not be deallocated. If
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*string* is a Unicode object, this function computes the default encoding of
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*string* and operates on that. If *string* is not a string object at all,
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:cfunc:`PyString_AsStringAndSize` returns ``-1`` and raises :exc:`TypeError`.
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.. cfunction:: void PyString_Concat(PyObject **string, PyObject *newpart)
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Create a new string object in *\*string* containing the contents of *newpart*
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appended to *string*; the caller will own the new reference. The reference to
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the old value of *string* will be stolen. If the new string cannot be created,
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the old reference to *string* will still be discarded and the value of
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*\*string* will be set to *NULL*; the appropriate exception will be set.
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.. cfunction:: void PyString_ConcatAndDel(PyObject **string, PyObject *newpart)
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Create a new string object in *\*string* containing the contents of *newpart*
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appended to *string*. This version decrements the reference count of *newpart*.
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.. cfunction:: int _PyString_Resize(PyObject **string, Py_ssize_t newsize)
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A way to resize a string object even though it is "immutable". Only use this to
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build up a brand new string object; don't use this if the string may already be
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known in other parts of the code. It is an error to call this function if the
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refcount on the input string object is not one. Pass the address of an existing
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string object as an lvalue (it may be written into), and the new size desired.
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On success, *\*string* holds the resized string object and ``0`` is returned;
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the address in *\*string* may differ from its input value. If the reallocation
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fails, the original string object at *\*string* is deallocated, *\*string* is
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set to *NULL*, a memory exception is set, and ``-1`` is returned.
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.. cfunction:: PyObject* PyString_Format(PyObject *format, PyObject *args)
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Return a new string object from *format* and *args*. Analogous to ``format %
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args``. The *args* argument must be a tuple.
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.. cfunction:: void PyString_InternInPlace(PyObject **string)
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Intern the argument *\*string* in place. The argument must be the address of a
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pointer variable pointing to a Python string object. If there is an existing
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interned string that is the same as *\*string*, it sets *\*string* to it
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(decrementing the reference count of the old string object and incrementing the
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reference count of the interned string object), otherwise it leaves *\*string*
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alone and interns it (incrementing its reference count). (Clarification: even
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though there is a lot of talk about reference counts, think of this function as
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reference-count-neutral; you own the object after the call if and only if you
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owned it before the call.)
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.. cfunction:: PyObject* PyString_InternFromString(const char *v)
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A combination of :cfunc:`PyString_FromString` and
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:cfunc:`PyString_InternInPlace`, returning either a new string object that has
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been interned, or a new ("owned") reference to an earlier interned string object
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with the same value.
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.. cfunction:: PyObject* PyString_Decode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)
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Create an object by decoding *size* bytes of the encoded buffer *s* using the
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codec registered for *encoding*. *encoding* and *errors* have the same meaning
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as the parameters of the same name in the :func:`unicode` built-in function.
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The codec to be used is looked up using the Python codec registry. Return
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*NULL* if an exception was raised by the codec.
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.. cfunction:: PyObject* PyString_AsDecodedObject(PyObject *str, const char *encoding, const char *errors)
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Decode a string object by passing it to the codec registered for *encoding* and
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return the result as Python object. *encoding* and *errors* have the same
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meaning as the parameters of the same name in the string :meth:`encode` method.
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The codec to be used is looked up using the Python codec registry. Return *NULL*
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if an exception was raised by the codec.
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.. cfunction:: PyObject* PyString_AsEncodedObject(PyObject *str, const char *encoding, const char *errors)
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Encode a string object using the codec registered for *encoding* and return the
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result as Python object. *encoding* and *errors* have the same meaning as the
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parameters of the same name in the string :meth:`encode` method. The codec to be
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used is looked up using the Python codec registry. Return *NULL* if an exception
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was raised by the codec.
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