1 .. highlightlang:: c

     2 

     3 .. _stringobjects:

     4 

     5 String/Bytes Objects

     6 --------------------

     7 

     8 These functions raise :exc:`TypeError` when expecting a string parameter and are

     9 called with a non-string parameter.

    10 

    11 .. note::

    12    These functions have been renamed to PyBytes_* in Python 3.x. The PyBytes

    13    names are also available in 2.6.

    14 

    15 .. index:: object: string

    16 

    17 

    18 .. ctype:: PyStringObject

    19 

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

    21 

    22 

    23 .. cvar:: PyTypeObject PyString_Type

    24 

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

    26 

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

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

    29 

    30 

    31 .. cfunction:: int PyString_Check(PyObject *o)

    32 

    33    Return true if the object *o* is a string object or an instance of a subtype of

    34    the string type.

    35 

    36    .. versionchanged:: 2.2

    37       Allowed subtypes to be accepted.

    38 

    39 

    40 .. cfunction:: int PyString_CheckExact(PyObject *o)

    41 

    42    Return true if the object *o* is a string object, but not an instance of a

    43    subtype of the string type.

    44 

    45    .. versionadded:: 2.2

    46 

    47 

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

    49 

    50    Return a new string object with a copy of the string *v* as value on success,

    51    and *NULL* on failure.  The parameter *v* must not be *NULL*; it will not be

    52    checked.

    53 

    54 

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

    56 

    57    Return a new string object with a copy of the string *v* as value and length

    58    *len* on success, and *NULL* on failure.  If *v* is *NULL*, the contents of the

    59    string are uninitialized.

    60 

    61 

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

    63 

    64    Take a C :cfunc:`printf`\ -style *format* string and a variable number of

    65    arguments, calculate the size of the resulting Python string and return a string

    66    with the values formatted into it.  The variable arguments must be C types and

    67    must correspond exactly to the format characters in the *format* string.  The

    68    following format characters are allowed:

    69 

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

    71    .. % One should just refer to the other.

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

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

    74    .. % when necessary via interpolating PY_FORMAT_SIZE_T.

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

    76 

    77    +-------------------+---------------+--------------------------------+

    78    | Format Characters | Type          | Comment                        |

    79    +===================+===============+================================+

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

    81    +-------------------+---------------+--------------------------------+

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

    83    |                   |               | represented as an C int.       |

    84    +-------------------+---------------+--------------------------------+

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

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

    87    +-------------------+---------------+--------------------------------+

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

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

    90    +-------------------+---------------+--------------------------------+

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

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

    93    +-------------------+---------------+--------------------------------+

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

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

    96    +-------------------+---------------+--------------------------------+

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

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

    99    +-------------------+---------------+--------------------------------+

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

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

   102    +-------------------+---------------+--------------------------------+

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

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

   105    +-------------------+---------------+--------------------------------+

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

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

   108    +-------------------+---------------+--------------------------------+

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

   110    |                   |               | array.                         |

   111    +-------------------+---------------+--------------------------------+

   112    | :attr:`%p`        | void\*        | The hex representation of a C  |

   113    |                   |               | pointer. Mostly equivalent to  |

   114    |                   |               | ``printf("%p")`` except that   |

   115    |                   |               | it is guaranteed to start with |

   116    |                   |               | the literal ``0x`` regardless  |

   117    |                   |               | of what the platform's         |

   118    |                   |               | ``printf`` yields.             |

   119    +-------------------+---------------+--------------------------------+

   120 

   121    An unrecognized format character causes all the rest of the format string to be

   122    copied as-is to the result string, and any extra arguments discarded.

   123 

   124 

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

   126 

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

   128    arguments.

   129 

   130 

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

   132 

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

   134 

   135 

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

   137 

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

   139 

   140 

   141 .. cfunction:: char* PyString_AsString(PyObject *string)

   142 

   143    Return a NUL-terminated representation of the contents of *string*.  The pointer

   144    refers to the internal buffer of *string*, not a copy.  The data must not be

   145    modified in any way, unless the string was just created using

   146    ``PyString_FromStringAndSize(NULL, size)``. It must not be deallocated.  If

   147    *string* is a Unicode object, this function computes the default encoding of

   148    *string* and operates on that.  If *string* is not a string object at all,

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

   150 

   151 

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

   153 

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

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

   156 

   157 

   158 .. cfunction:: int PyString_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)

   159 

   160    Return a NUL-terminated representation of the contents of the object *obj*

   161    through the output variables *buffer* and *length*.

   162 

   163    The function accepts both string and Unicode objects as input. For Unicode

   164    objects it returns the default encoded version of the object.  If *length* is

   165    *NULL*, the resulting buffer may not contain NUL characters; if it does, the

   166    function returns ``-1`` and a :exc:`TypeError` is raised.

   167 

   168    The buffer refers to an internal string buffer of *obj*, not a copy. The data

   169    must not be modified in any way, unless the string was just created using

   170    ``PyString_FromStringAndSize(NULL, size)``.  It must not be deallocated.  If

   171    *string* is a Unicode object, this function computes the default encoding of

   172    *string* and operates on that.  If *string* is not a string object at all,

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

   174 

   175 

   176 .. cfunction:: void PyString_Concat(PyObject **string, PyObject *newpart)

   177 

   178    Create a new string object in *\*string* containing the contents of *newpart*

   179    appended to *string*; the caller will own the new reference.  The reference to

   180    the old value of *string* will be stolen.  If the new string cannot be created,

   181    the old reference to *string* will still be discarded and the value of

   182    *\*string* will be set to *NULL*; the appropriate exception will be set.

   183 

   184 

   185 .. cfunction:: void PyString_ConcatAndDel(PyObject **string, PyObject *newpart)

   186 

   187    Create a new string object in *\*string* containing the contents of *newpart*

   188    appended to *string*.  This version decrements the reference count of *newpart*.

   189 

   190 

   191 .. cfunction:: int _PyString_Resize(PyObject **string, Py_ssize_t newsize)

   192 

   193    A way to resize a string object even though it is "immutable". Only use this to

   194    build up a brand new string object; don't use this if the string may already be

   195    known in other parts of the code.  It is an error to call this function if the

   196    refcount on the input string object is not one. Pass the address of an existing

   197    string object as an lvalue (it may be written into), and the new size desired.

   198    On success, *\*string* holds the resized string object and ``0`` is returned;

   199    the address in *\*string* may differ from its input value.  If the reallocation

   200    fails, the original string object at *\*string* is deallocated, *\*string* is

   201    set to *NULL*, a memory exception is set, and ``-1`` is returned.

   202 

   203 

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

   205 

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

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

   208 

   209 

   210 .. cfunction:: void PyString_InternInPlace(PyObject **string)

   211 

   212    Intern the argument *\*string* in place.  The argument must be the address of a

   213    pointer variable pointing to a Python string object.  If there is an existing

   214    interned string that is the same as *\*string*, it sets *\*string* to it

   215    (decrementing the reference count of the old string object and incrementing the

   216    reference count of the interned string object), otherwise it leaves *\*string*

   217    alone and interns it (incrementing its reference count).  (Clarification: even

   218    though there is a lot of talk about reference counts, think of this function as

   219    reference-count-neutral; you own the object after the call if and only if you

   220    owned it before the call.)

   221 

   222 

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

   224 

   225    A combination of :cfunc:`PyString_FromString` and

   226    :cfunc:`PyString_InternInPlace`, returning either a new string object that has

   227    been interned, or a new ("owned") reference to an earlier interned string object

   228    with the same value.

   229 

   230 

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

   232 

   233    Create an object by decoding *size* bytes of the encoded buffer *s* using the

   234    codec registered for *encoding*.  *encoding* and *errors* have the same meaning

   235    as the parameters of the same name in the :func:`unicode` built-in function.

   236    The codec to be used is looked up using the Python codec registry.  Return

   237    *NULL* if an exception was raised by the codec.

   238 

   239 

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

   241 

   242    Decode a string object by passing it to the codec registered for *encoding* and

   243    return the result as Python object. *encoding* and *errors* have the same

   244    meaning as the parameters of the same name in the string :meth:`encode` method.

   245    The codec to be used is looked up using the Python codec registry. Return *NULL*

   246    if an exception was raised by the codec.

   247 

   248 

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

   250 

   251    Encode the :ctype:`char` buffer of the given size by passing it to the codec

   252    registered for *encoding* and return a Python object. *encoding* and *errors*

   253    have the same meaning as the parameters of the same name in the string

   254    :meth:`encode` method. The codec to be used is looked up using the Python codec

   255    registry.  Return *NULL* if an exception was raised by the codec.

   256 

   257 

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

   259 

   260    Encode a string object using the codec registered for *encoding* and return the

   261    result as Python object. *encoding* and *errors* have the same meaning as the

   262    parameters of the same name in the string :meth:`encode` method. The codec to be

   263    used is looked up using the Python codec registry. Return *NULL* if an exception

   264    was raised by the codec.