.. highlightlang:: c

.. _stringobjects:

String/Bytes Objects

--------------------

These functions raise :exc:`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. The PyBytes

   names are also available in 2.6.

.. index:: object: string

.. ctype:: PyStringObject

   This subtype of :ctype:`PyObject` represents a Python string object.

.. cvar:: PyTypeObject PyString_Type

   .. index:: single: StringType (in module types)

   This instance of :ctype:`PyTypeObject` represents the Python string type; it is

   the same object as ``str`` and ``types.StringType`` in the Python layer. .

.. cfunction:: 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.

   .. versionchanged:: 2.2

      Allowed subtypes to be accepted.

.. cfunction:: 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.

   .. versionadded:: 2.2

.. cfunction:: PyObject* PyString_FromString(const char *v)

   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.

.. cfunction:: PyObject* PyString_FromStringAndSize(const char *v, Py_ssize_t len)

   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.

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

   Take a C :cfunc:`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:

   .. % This should be exactly the same as the table in PyErr_Format.

   .. % One should just refer to the other.

   .. % The descriptions for %zd and %zu are wrong, but the truth is complicated

   .. % because not all compilers support the %z width modifier -- we fake it

   .. % when necessary via interpolating PY_FORMAT_SIZE_T.

   .. % %u, %lu, %zu should have "new in Python 2.5" blurbs.

   +-------------------+---------------+--------------------------------+

   | Format Characters | Type          | Comment                        |

   +===================+===============+================================+

   | :attr:`%%`        | *n/a*         | The literal % character.       |

   +-------------------+---------------+--------------------------------+

   | :attr:`%c`        | int           | A single character,            |

   |                   |               | represented as an C int.       |

   +-------------------+---------------+--------------------------------+

   | :attr:`%d`        | int           | Exactly equivalent to          |

   |                   |               | ``printf("%d")``.              |

   +-------------------+---------------+--------------------------------+

   | :attr:`%u`        | unsigned int  | Exactly equivalent to          |

   |                   |               | ``printf("%u")``.              |

   +-------------------+---------------+--------------------------------+

   | :attr:`%ld`       | long          | Exactly equivalent to          |

   |                   |               | ``printf("%ld")``.             |

   +-------------------+---------------+--------------------------------+

   | :attr:`%lu`       | unsigned long | Exactly equivalent to          |

   |                   |               | ``printf("%lu")``.             |

   +-------------------+---------------+--------------------------------+

   | :attr:`%zd`       | Py_ssize_t    | Exactly equivalent to          |

   |                   |               | ``printf("%zd")``.             |

   +-------------------+---------------+--------------------------------+

   | :attr:`%zu`       | size_t        | Exactly equivalent to          |

   |                   |               | ``printf("%zu")``.             |

   +-------------------+---------------+--------------------------------+

   | :attr:`%i`        | int           | Exactly equivalent to          |

   |                   |               | ``printf("%i")``.              |

   +-------------------+---------------+--------------------------------+

   | :attr:`%x`        | int           | Exactly equivalent to          |

   |                   |               | ``printf("%x")``.              |

   +-------------------+---------------+--------------------------------+

   | :attr:`%s`        | char\*        | A null-terminated C character  |

   |                   |               | array.                         |

   +-------------------+---------------+--------------------------------+

   | :attr:`%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.

.. cfunction:: PyObject* PyString_FromFormatV(const char *format, va_list vargs)

   Identical to :cfunc:`PyString_FromFormat` except that it takes exactly two

   arguments.

.. cfunction:: Py_ssize_t PyString_Size(PyObject *string)

   Return the length of the string in string object *string*.

.. cfunction:: Py_ssize_t PyString_GET_SIZE(PyObject *string)

   Macro form of :cfunc:`PyString_Size` but without error checking.

.. cfunction:: 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,

   :cfunc:`PyString_AsString` returns *NULL* and raises :exc:`TypeError`.

.. cfunction:: char* PyString_AS_STRING(PyObject *string)

   Macro form of :cfunc:`PyString_AsString` but without error checking.  Only

   string objects are supported; no Unicode objects should be passed.

.. cfunction:: 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 :exc:`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,

   :cfunc:`PyString_AsStringAndSize` returns ``-1`` and raises :exc:`TypeError`.

.. cfunction:: 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.

.. cfunction:: 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*.

.. cfunction:: 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.

.. cfunction:: PyObject* PyString_Format(PyObject *format, PyObject *args)

   Return a new string object from *format* and *args*. Analogous to ``format %

   args``.  The *args* argument must be a tuple.

.. cfunction:: 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.)

.. cfunction:: PyObject* PyString_InternFromString(const char *v)

   A combination of :cfunc:`PyString_FromString` and

   :cfunc:`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.

.. cfunction:: PyObject* PyString_Decode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)

   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 :func:`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.

.. cfunction:: PyObject* PyString_AsDecodedObject(PyObject *str, const char *encoding, const char *errors)

   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 :meth:`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.

.. cfunction:: PyObject* PyString_Encode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)

   Encode the :ctype:`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

   :meth:`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.

.. cfunction:: PyObject* PyString_AsEncodedObject(PyObject *str, const char *encoding, const char *errors)

   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 :meth:`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.