mirror of https://github.com/python/cpython
180 lines
6.0 KiB
ReStructuredText
180 lines
6.0 KiB
ReStructuredText
.. highlightlang:: c
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.. _fileobjects:
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File Objects
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------------
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.. index:: object: file
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Python's built-in file objects are implemented entirely on the :c:type:`FILE\*`
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support from the C standard library. This is an implementation detail and may
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change in future releases of Python.
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.. c:type:: PyFileObject
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This subtype of :c:type:`PyObject` represents a Python file object.
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.. c:var:: PyTypeObject PyFile_Type
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.. index:: single: FileType (in module types)
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This instance of :c:type:`PyTypeObject` represents the Python file type. This is
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exposed to Python programs as ``file`` and ``types.FileType``.
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.. c:function:: int PyFile_Check(PyObject *p)
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Return true if its argument is a :c:type:`PyFileObject` or a subtype of
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:c:type:`PyFileObject`.
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.. versionchanged:: 2.2
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Allowed subtypes to be accepted.
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.. c:function:: int PyFile_CheckExact(PyObject *p)
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Return true if its argument is a :c:type:`PyFileObject`, but not a subtype of
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:c:type:`PyFileObject`.
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.. versionadded:: 2.2
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.. c:function:: PyObject* PyFile_FromString(char *filename, char *mode)
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.. index:: single: fopen()
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On success, return a new file object that is opened on the file given by
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*filename*, with a file mode given by *mode*, where *mode* has the same
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semantics as the standard C routine :c:func:`fopen`. On failure, return *NULL*.
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.. c:function:: PyObject* PyFile_FromFile(FILE *fp, char *name, char *mode, int (*close)(FILE*))
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Create a new :c:type:`PyFileObject` from the already-open standard C file
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pointer, *fp*. The function *close* will be called when the file should be
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closed. Return *NULL* and close the file using *close* on failure.
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*close* is optional and can be set to *NULL*.
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.. c:function:: FILE* PyFile_AsFile(PyObject \*p)
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Return the file object associated with *p* as a :c:type:`FILE\*`.
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If the caller will ever use the returned :c:type:`FILE\*` object while
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the :term:`GIL` is released it must also call the :c:func:`PyFile_IncUseCount` and
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:c:func:`PyFile_DecUseCount` functions described below as appropriate.
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.. c:function:: void PyFile_IncUseCount(PyFileObject \*p)
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Increments the PyFileObject's internal use count to indicate
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that the underlying :c:type:`FILE\*` is being used.
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This prevents Python from calling f_close() on it from another thread.
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Callers of this must call :c:func:`PyFile_DecUseCount` when they are
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finished with the :c:type:`FILE\*`. Otherwise the file object will
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never be closed by Python.
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The :term:`GIL` must be held while calling this function.
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The suggested use is to call this after :c:func:`PyFile_AsFile` and before
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you release the GIL::
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FILE *fp = PyFile_AsFile(p);
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PyFile_IncUseCount(p);
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/* ... */
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Py_BEGIN_ALLOW_THREADS
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do_something(fp);
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Py_END_ALLOW_THREADS
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/* ... */
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PyFile_DecUseCount(p);
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.. versionadded:: 2.6
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.. c:function:: void PyFile_DecUseCount(PyFileObject \*p)
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Decrements the PyFileObject's internal unlocked_count member to
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indicate that the caller is done with its own use of the :c:type:`FILE\*`.
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This may only be called to undo a prior call to :c:func:`PyFile_IncUseCount`.
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The :term:`GIL` must be held while calling this function (see the example
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above).
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.. versionadded:: 2.6
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.. c:function:: PyObject* PyFile_GetLine(PyObject *p, int n)
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.. index:: single: EOFError (built-in exception)
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Equivalent to ``p.readline([n])``, this function reads one line from the
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object *p*. *p* may be a file object or any object with a :meth:`readline`
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method. If *n* is ``0``, exactly one line is read, regardless of the length of
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the line. If *n* is greater than ``0``, no more than *n* bytes will be read
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from the file; a partial line can be returned. In both cases, an empty string
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is returned if the end of the file is reached immediately. If *n* is less than
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``0``, however, one line is read regardless of length, but :exc:`EOFError` is
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raised if the end of the file is reached immediately.
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.. c:function:: PyObject* PyFile_Name(PyObject *p)
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Return the name of the file specified by *p* as a string object.
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.. c:function:: void PyFile_SetBufSize(PyFileObject *p, int n)
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.. index:: single: setvbuf()
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Available on systems with :c:func:`setvbuf` only. This should only be called
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immediately after file object creation.
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.. c:function:: int PyFile_SetEncoding(PyFileObject *p, const char *enc)
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Set the file's encoding for Unicode output to *enc*. Return 1 on success and 0
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on failure.
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.. versionadded:: 2.3
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.. c:function:: int PyFile_SetEncodingAndErrors(PyFileObject *p, const char *enc, *errors)
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Set the file's encoding for Unicode output to *enc*, and its error
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mode to *err*. Return 1 on success and 0 on failure.
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.. versionadded:: 2.6
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.. c:function:: int PyFile_SoftSpace(PyObject *p, int newflag)
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.. index:: single: softspace (file attribute)
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This function exists for internal use by the interpreter. Set the
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:attr:`softspace` attribute of *p* to *newflag* and return the previous value.
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*p* does not have to be a file object for this function to work properly; any
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object is supported (thought its only interesting if the :attr:`softspace`
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attribute can be set). This function clears any errors, and will return ``0``
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as the previous value if the attribute either does not exist or if there were
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errors in retrieving it. There is no way to detect errors from this function,
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but doing so should not be needed.
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.. c:function:: int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)
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.. index:: single: Py_PRINT_RAW
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Write object *obj* to file object *p*. The only supported flag for *flags* is
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:const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
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instead of the :func:`repr`. Return ``0`` on success or ``-1`` on failure; the
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appropriate exception will be set.
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.. c:function:: int PyFile_WriteString(const char *s, PyObject *p)
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Write string *s* to file object *p*. Return ``0`` on success or ``-1`` on
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failure; the appropriate exception will be set.
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