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123 lines
4.4 KiB
ReStructuredText
123 lines
4.4 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 :ctype:`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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.. ctype:: PyFileObject
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This subtype of :ctype:`PyObject` represents a Python file object.
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.. cvar:: PyTypeObject PyFile_Type
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.. index:: single: FileType (in module types)
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This instance of :ctype:`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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.. cfunction:: int PyFile_Check(PyObject *p)
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Return true if its argument is a :ctype:`PyFileObject` or a subtype of
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:ctype:`PyFileObject`.
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.. cfunction:: int PyFile_CheckExact(PyObject *p)
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Return true if its argument is a :ctype:`PyFileObject`, but not a subtype of
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:ctype:`PyFileObject`.
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.. cfunction:: PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding, char *newline, int closefd)
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Create a new :ctype:`PyFileObject` from the file descriptor of an already
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opened file *fd*. The arguments *name*, *encoding* and *newline* can be
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*NULL* to use the defaults; *buffering* can be *-1* to use the default.
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Return *NULL* on failure.
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.. warning::
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Take care when you are mixing streams and descriptors! For more
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information, see `the GNU C Library docs
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<http://www.gnu.org/software/libc/manual/html_node/Stream_002fDescriptor-Precautions.html#Stream_002fDescriptor-Precautions>`_.
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.. cfunction:: int PyObject_AsFileDescriptor(PyObject *p)
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Return the file descriptor associated with *p* as an :ctype:`int`. If the
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object is an integer, its value is returned. If not, the
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object's :meth:`fileno` method is called if it exists; the method must return
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an integer, which is returned as the file descriptor value. Sets an
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exception and returns ``-1`` on failure.
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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: void PyFile_SetBufSize(PyFileObject *p, int n)
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.. index:: single: setvbuf()
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Available on systems with :cfunc:`setvbuf` only. This should only be called
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immediately after file object creation.
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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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.. cfunction:: 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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