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python-3.7.4-docs-html/_sources/c-api/file.rst.txt

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+.. highlightlang:: c
+
+.. _fileobjects:
+
+File Objects
+------------
+
+.. index:: object: file
+
+These APIs are a minimal emulation of the Python 2 C API for built-in file
+objects, which used to rely on the buffered I/O (:c:type:`FILE\*`) support
+from the C standard library.  In Python 3, files and streams use the new
+:mod:`io` module, which defines several layers over the low-level unbuffered
+I/O of the operating system.  The functions described below are
+convenience C wrappers over these new APIs, and meant mostly for internal
+error reporting in the interpreter; third-party code is advised to access
+the :mod:`io` APIs instead.
+
+
+.. c:function:: PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const char *encoding, const char *errors, const char *newline, int closefd)
+
+   Create a Python file object from the file descriptor of an already
+   opened file *fd*.  The arguments *name*, *encoding*, *errors* and *newline*
+   can be *NULL* to use the defaults; *buffering* can be *-1* to use the
+   default. *name* is ignored and kept for backward compatibility. Return
+   *NULL* on failure. For a more comprehensive description of the arguments,
+   please refer to the :func:`io.open` function documentation.
+
+   .. warning::
+
+     Since Python streams have their own buffering layer, mixing them with
+     OS-level file descriptors can produce various issues (such as unexpected
+     ordering of data).
+
+   .. versionchanged:: 3.2
+      Ignore *name* attribute.
+
+
+.. c:function:: int PyObject_AsFileDescriptor(PyObject *p)
+
+   Return the file descriptor associated with *p* as an :c:type:`int`.  If the
+   object is an integer, its value is returned.  If not, the
+   object's :meth:`~io.IOBase.fileno` method is called if it exists; the
+   method must return an integer, which is returned as the file descriptor
+   value.  Sets an exception and returns ``-1`` on failure.
+
+
+.. c:function:: PyObject* PyFile_GetLine(PyObject *p, int n)
+
+   .. index:: single: EOFError (built-in exception)
+
+   Equivalent to ``p.readline([n])``, this function reads one line from the
+   object *p*.  *p* may be a file object or any object with a
+   :meth:`~io.IOBase.readline`
+   method.  If *n* is ``0``, exactly one line is read, regardless of the length of
+   the line.  If *n* is greater than ``0``, no more than *n* bytes will be read
+   from the file; a partial line can be returned.  In both cases, an empty string
+   is returned if the end of the file is reached immediately.  If *n* is less than
+   ``0``, however, one line is read regardless of length, but :exc:`EOFError` is
+   raised if the end of the file is reached immediately.
+
+
+.. c:function:: int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)
+
+   .. index:: single: Py_PRINT_RAW
+
+   Write object *obj* to file object *p*.  The only supported flag for *flags* is
+   :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
+   instead of the :func:`repr`.  Return ``0`` on success or ``-1`` on failure; the
+   appropriate exception will be set.
+
+
+.. c:function:: int PyFile_WriteString(const char *s, PyObject *p)
+
+   Write string *s* to file object *p*.  Return ``0`` on success or ``-1`` on
+   failure; the appropriate exception will be set.