1 .. highlightlang:: c

     2 

     3 .. _fileobjects:

     4 

     5 File Objects

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

     7 

     8 .. index:: object: file

     9 

    10 Python's built-in file objects are implemented entirely on the :ctype:`FILE\*`

    11 support from the C standard library.  This is an implementation detail and may

    12 change in future releases of Python.

    13 

    14 

    15 .. ctype:: PyFileObject

    16 

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

    18 

    19 

    20 .. cvar:: PyTypeObject PyFile_Type

    21 

    22    .. index:: single: FileType (in module types)

    23 

    24    This instance of :ctype:`PyTypeObject` represents the Python file type.  This is

    25    exposed to Python programs as ``file`` and ``types.FileType``.

    26 

    27 

    28 .. cfunction:: int PyFile_Check(PyObject *p)

    29 

    30    Return true if its argument is a :ctype:`PyFileObject` or a subtype of

    31    :ctype:`PyFileObject`.

    32 

    33    .. versionchanged:: 2.2

    34       Allowed subtypes to be accepted.

    35 

    36 

    37 .. cfunction:: int PyFile_CheckExact(PyObject *p)

    38 

    39    Return true if its argument is a :ctype:`PyFileObject`, but not a subtype of

    40    :ctype:`PyFileObject`.

    41 

    42    .. versionadded:: 2.2

    43 

    44 

    45 .. cfunction:: PyObject* PyFile_FromString(char *filename, char *mode)

    46 

    47    .. index:: single: fopen()

    48 

    49    On success, return a new file object that is opened on the file given by

    50    *filename*, with a file mode given by *mode*, where *mode* has the same

    51    semantics as the standard C routine :cfunc:`fopen`.  On failure, return *NULL*.

    52 

    53 

    54 .. cfunction:: PyObject* PyFile_FromFile(FILE *fp, char *name, char *mode, int (*close)(FILE*))

    55 

    56    Create a new :ctype:`PyFileObject` from the already-open standard C file

    57    pointer, *fp*.  The function *close* will be called when the file should be

    58    closed.  Return *NULL* on failure.

    59 

    60 

    61 .. cfunction:: FILE* PyFile_AsFile(PyObject \*p)

    62 

    63    Return the file object associated with *p* as a :ctype:`FILE\*`.

    64 

    65    If the caller will ever use the returned :ctype:`FILE\*` object while

    66    the GIL is released it must also call the `PyFile_IncUseCount` and

    67    `PyFile_DecUseCount` functions described below as appropriate.

    68 

    69 

    70 .. cfunction:: void PyFile_IncUseCount(PyFileObject \*p)

    71 

    72    Increments the PyFileObject's internal use count to indicate

    73    that the underlying :ctype:`FILE\*` is being used.

    74    This prevents Python from calling f_close() on it from another thread.

    75    Callers of this must call `PyFile_DecUseCount` when they are

    76    finished with the :ctype:`FILE\*`.  Otherwise the file object will

    77    never be closed by Python.

    78 

    79    The GIL must be held while calling this function.

    80 

    81    The suggested use is to call this after `PyFile_AsFile` just before

    82    you release the GIL.

    83 

    84    .. versionadded:: 2.6

    85 

    86 

    87 .. cfunction:: void PyFile_DecUseCount(PyFileObject \*p)

    88 

    89    Decrements the PyFileObject's internal unlocked_count member to

    90    indicate that the caller is done with its own use of the :ctype:`FILE\*`.

    91    This may only be called to undo a prior call to `PyFile_IncUseCount`.

    92 

    93    The GIL must be held while calling this function.

    94 

    95    .. versionadded:: 2.6

    96 

    97 

    98 .. cfunction:: PyObject* PyFile_GetLine(PyObject *p, int n)

    99 

   100    .. index:: single: EOFError (built-in exception)

   101 

   102    Equivalent to ``p.readline([n])``, this function reads one line from the

   103    object *p*.  *p* may be a file object or any object with a :meth:`readline`

   104    method.  If *n* is ``0``, exactly one line is read, regardless of the length of

   105    the line.  If *n* is greater than ``0``, no more than *n* bytes will be read

   106    from the file; a partial line can be returned.  In both cases, an empty string

   107    is returned if the end of the file is reached immediately.  If *n* is less than

   108    ``0``, however, one line is read regardless of length, but :exc:`EOFError` is

   109    raised if the end of the file is reached immediately.

   110 

   111 

   112 .. cfunction:: PyObject* PyFile_Name(PyObject *p)

   113 

   114    Return the name of the file specified by *p* as a string object.

   115 

   116 

   117 .. cfunction:: void PyFile_SetBufSize(PyFileObject *p, int n)

   118 

   119    .. index:: single: setvbuf()

   120 

   121    Available on systems with :cfunc:`setvbuf` only.  This should only be called

   122    immediately after file object creation.

   123 

   124 

   125 .. cfunction:: int PyFile_SetEncoding(PyFileObject *p, const char *enc)

   126 

   127    Set the file's encoding for Unicode output to *enc*. Return 1 on success and 0

   128    on failure.

   129 

   130    .. versionadded:: 2.3

   131 

   132 

   133 .. cfunction:: int PyFile_SetEncodingAndErrors(PyFileObject *p, const char *enc, *errors)

   134 

   135    Set the file's encoding for Unicode output to *enc*, and its error

   136    mode to *err*. Return 1 on success and 0 on failure.

   137 

   138    .. versionadded:: 2.6

   139 

   140 

   141 .. cfunction:: int PyFile_SoftSpace(PyObject *p, int newflag)

   142 

   143    .. index:: single: softspace (file attribute)

   144 

   145    This function exists for internal use by the interpreter.  Set the

   146    :attr:`softspace` attribute of *p* to *newflag* and return the previous value.

   147    *p* does not have to be a file object for this function to work properly; any

   148    object is supported (thought its only interesting if the :attr:`softspace`

   149    attribute can be set).  This function clears any errors, and will return ``0``

   150    as the previous value if the attribute either does not exist or if there were

   151    errors in retrieving it.  There is no way to detect errors from this function,

   152    but doing so should not be needed.

   153 

   154 

   155 .. cfunction:: int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)

   156 

   157    .. index:: single: Py_PRINT_RAW

   158 

   159    Write object *obj* to file object *p*.  The only supported flag for *flags* is

   160    :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written

   161    instead of the :func:`repr`.  Return ``0`` on success or ``-1`` on failure; the

   162    appropriate exception will be set.

   163 

   164 

   165 .. cfunction:: int PyFile_WriteString(const char *s, PyObject *p)

   166 

   167    Write string *s* to file object *p*.  Return ``0`` on success or ``-1`` on

   168    failure; the appropriate exception will be set.