7.3.1 String Objects

Python 2.5

previous page next page

7.3.1 String Objects

These functions raise TypeError when expecting a string parameter and are called with a non-string parameter.

PyStringObject: This subtype of PyObject represents a Python string object.

PyTypeObject PyString_Type: This instance of PyTypeObject represents the Python string type; it is the same object as str and types.StringType in the Python layer. .

int PyString_Check( PyObject *o): Return true if the object o is a string object or an instance of a subtype of the string type. Changed in version 2.2: Allowed subtypes to be accepted.

int PyString_CheckExact( PyObject *o): Return true if the object o is a string object, but not an instance of a subtype of the string type. New in version 2.2.

PyObject* PyString_FromString( const char *v): Return value: New reference.
Return a new string object with the value v on success, and NULL on failure. The parameter v must not be NULL; it will not be checked.

PyObject* PyString_FromStringAndSize( const char *v, Py_ssize_t len): Return value: New reference.
Return a new string object with the value v and length len on success, and NULL on failure. If v is NULL, the contents of the string are uninitialized.

PyObject* PyString_FromFormat( const char *format, ...)

Return value: New reference.

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

Format Characters	Type	Comment
`%%`	n/a	The literal % character.
`%c`	int	A single character, represented as an C int.
`%d`	int	Exactly equivalent to `printf("%d")`.
`%u`	unsigned int	Exactly equivalent to `printf("%u")`.
`%ld`	long	Exactly equivalent to `printf("%ld")`.
`%lu`	unsigned long	Exactly equivalent to `printf("%lu")`.
`%zd`	Py_ssize_t	Exactly equivalent to `printf("%zd")`.
`%zu`	size_t	Exactly equivalent to `printf("%zu")`.
`%i`	int	Exactly equivalent to `printf("%i")`.
`%x`	int	Exactly equivalent to `printf("%x")`.
`%s`	char*	A null-terminated C character array.
`%p`	void*	The hex representation of a C pointer. Mostly equivalent to `printf("%p")` except that it is guaranteed to start with the literal `0x` regardless of what the platform's `printf` yields.

An unrecognized format character causes all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded.

PyObject* PyString_FromFormatV( const char *format, va_list vargs): Return value: New reference.
Identical to PyString_FromFormat() except that it takes exactly two arguments.

Py_ssize_t PyString_Size( PyObject *string): Return the length of the string in string object string.

Py_ssize_t PyString_GET_SIZE( PyObject *string): Macro form of PyString_Size() but without error checking.

char* PyString_AsString( PyObject *string): Return a NUL-terminated representation of the contents of string. The pointer refers to the internal buffer of string, not a copy. The data must not be modified in any way, unless the string was just created using PyString_FromStringAndSize(NULL, size). It must not be deallocated. If string is a Unicode object, this function computes the default encoding of string and operates on that. If string is not a string object at all, PyString_AsString() returns NULL and raises TypeError.

char* PyString_AS_STRING( PyObject *string): Macro form of PyString_AsString() but without error checking. Only string objects are supported; no Unicode objects should be passed.

int PyString_AsStringAndSize( PyObject *obj, char **buffer, Py_ssize_t *length)

Return a NUL-terminated representation of the contents of the object obj through the output variables buffer and length.

The function accepts both string and Unicode objects as input. For Unicode objects it returns the default encoded version of the object. If length is NULL, the resulting buffer may not contain NUL characters; if it does, the function returns -1 and a TypeError is raised.

The buffer refers to an internal string buffer of obj, not a copy. The data must not be modified in any way, unless the string was just created using PyString_FromStringAndSize(NULL, size). It must not be deallocated. If string is a Unicode object, this function computes the default encoding of string and operates on that. If string is not a string object at all, PyString_AsStringAndSize() returns -1 and raises TypeError.

void PyString_Concat( PyObject **string, PyObject *newpart): Create a new string object in *string containing the contents of newpart appended to string; the caller will own the new reference. The reference to the old value of string will be stolen. If the new string cannot be created, the old reference to string will still be discarded and the value of *string will be set to NULL; the appropriate exception will be set.

void PyString_ConcatAndDel( PyObject **string, PyObject *newpart): Create a new string object in *string containing the contents of newpart appended to string. This version decrements the reference count of newpart.

int _PyString_Resize( PyObject **string, Py_ssize_t newsize): A way to resize a string object even though it is ``immutable''. Only use this to build up a brand new string object; don't use this if the string may already be known in other parts of the code. It is an error to call this function if the refcount on the input string object is not one. Pass the address of an existing string object as an lvalue (it may be written into), and the new size desired. On success, *string holds the resized string object and 0 is returned; the address in *string may differ from its input value. If the reallocation fails, the original string object at *string is deallocated, *string is set to NULL, a memory exception is set, and -1 is returned.

PyObject* PyString_Format( PyObject *format, PyObject *args): Return value: New reference.
Return a new string object from format and args. Analogous to format % args. The args argument must be a tuple.

void PyString_InternInPlace( PyObject **string): Intern the argument *string in place. The argument must be the address of a pointer variable pointing to a Python 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* PyString_InternFromString( const char *v): Return value: New reference.
A combination of PyString_FromString() and PyString_InternInPlace(), returning either a new string object that has been interned, or a new (``owned'') reference to an earlier interned string object with the same value.

PyObject* PyString_Decode( const char *s, Py_ssize_t size, const char *encoding, const char *errors): Return value: New reference.
Create an object by decoding size bytes of the encoded buffer s using the codec registered for encoding. encoding and errors have the same meaning as the parameters of the same name in the unicode() built-in function. The codec to be used is looked up using the Python codec registry. Return NULL if an exception was raised by the codec.

PyObject* PyString_AsDecodedObject( PyObject *str, const char *encoding, const char *errors): Return value: New reference.
Decode a string object by passing it to the codec registered for encoding and return the result as Python object. encoding and errors have the same meaning as the parameters of the same name in the string 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* PyString_Encode( const char *s, Py_ssize_t size, const char *encoding, const char *errors): Return value: New reference.
Encode the char buffer of the given size by passing it to the codec registered for encoding and return a Python object. encoding and errors have the same meaning as the parameters of the same name in the string 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* PyString_AsEncodedObject( PyObject *str, const char *encoding, const char *errors): Return value: New reference.
Encode a string object using the codec registered for encoding and return the result as Python object. encoding and errors have the same meaning as the parameters of the same name in the string 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.

See About this document... for information on suggesting changes.

previous page start next page