String/Bytes Objects — Python 2.7.18 documentation

This document is for an old version of Python that is no longer supported. You should upgrade and read the Python documentation for the current stable release.

# String/Bytes Objects

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

Note

These functions have been renamed to PyBytes_* in Python 3.x. Unless otherwise noted, the PyBytes functions available in 3.x are aliased to their PyString_* equivalents to help porting.

`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 a copy of the string v as value 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 a copy of the string v as value and length len on success, and NULL on failure. If v is NULL, the contents of the string are uninitialized.

  Changed in version 2.5: This function used an `int` type for len. This might require changes in your code for properly supporting 64-bit systems.

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 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")`.
  `%lu` | unsigned long | Exactly equivalent to `printf("%lu")`.
  `%lld` | long long | Exactly equivalent to `printf("%lld")`.
  `%llu` | unsigned long long | Exactly equivalent to `printf("%llu")`.
  `%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.

  Note

  The “%lld” and “%llu” format specifiers are only available when `HAVE_LONG_LONG` is defined.

  Changed in version 2.7: Support for “%lld” and “%llu” added.

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.

  Changed in version 2.5: This function returned an `int` type. This might require changes in your code for properly supporting 64-bit systems.

Py_ssize_t `PyString_GET_SIZE`(PyObject *string)

  Macro form of `PyString_Size()` but without error checking.

  Changed in version 2.5: This macro returned an `int` type. This might require changes in your code for properly supporting 64-bit systems.

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`.

  Changed in version 2.5: This function used an `int *` type for length. This might require changes in your code for properly supporting 64-bit systems.

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.

  Changed in version 2.5: This function used an `int` type for newsize. This might require changes in your code for properly supporting 64-bit systems.

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 or dict.

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.)

  Note

  This function is not available in 3.x and does not have a PyBytes alias.

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.

  Note

  This function is not available in 3.x and does not have a PyBytes alias.

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.

  Note

  This function is not available in 3.x and does not have a PyBytes alias.

  Changed in version 2.5: This function used an `int` type for size. This might require changes in your code for properly supporting 64-bit systems.

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.

  Note

  This function is not available in 3.x and does not have a PyBytes alias.

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.

  Note

  This function is not available in 3.x and does not have a PyBytes alias.

  Changed in version 2.5: This function used an `int` type for size. This might require changes in your code for properly supporting 64-bit systems.

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.

  Note

  This function is not available in 3.x and does not have a PyBytes alias.