72 lines
3.0 KiB
ReStructuredText
72 lines
3.0 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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These APIs are a minimal emulation of the Python 2 C API for built-in file
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objects, which used to rely on the buffered I/O (:ctype:`FILE\*`) support
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from the C standard library. In Python 3, files and streams use the new
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:mod:`io` module, which defines several layers over the low-level unbuffered
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I/O of the operating system. The functions described below are
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convenience C wrappers over these new APIs, and meant mostly for internal
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error reporting in the interpreter; third-party code is advised to access
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the :mod:`io` APIs instead.
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.. cfunction:: PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding, char *errors, char *newline, int closefd)
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Create a Python file object from the file descriptor of an already
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opened file *fd*. The arguments *name*, *encoding*, *errors* and *newline*
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can be *NULL* to use the defaults; *buffering* can be *-1* to use the
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default. Return *NULL* on failure. For a more comprehensive description of
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the arguments, please refer to the :func:`io.open` function documentation.
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.. warning::
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Since Python streams have their own buffering layer, mixing them with
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OS-level file descriptors can produce various issues (such as unexpected
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ordering of data).
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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:: 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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