mirror of https://github.com/python/cpython
103 lines
4.2 KiB
ReStructuredText
103 lines
4.2 KiB
ReStructuredText
.. highlight:: 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 (:c:type:`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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.. 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)
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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. *name* is ignored and kept for backward compatibility. Return
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``NULL`` on failure. For a more comprehensive description of the arguments,
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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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.. versionchanged:: 3.2
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Ignore *name* attribute.
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.. c:function:: int PyObject_AsFileDescriptor(PyObject *p)
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Return the file descriptor associated with *p* as an :c:type:`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:`~io.IOBase.fileno` method is called if it exists; the
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method must return an integer, which is returned as the file descriptor
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value. Sets an exception and returns ``-1`` on failure.
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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
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:meth:`~io.IOBase.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:: int PyFile_SetOpenCodeHook(Py_OpenCodeHookFunction handler)
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Overrides the normal behavior of :func:`io.open_code` to pass its parameter
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through the provided handler.
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The handler is a function of type :c:type:`PyObject *(\*)(PyObject *path,
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void *userData)`, where *path* is guaranteed to be :c:type:`PyUnicodeObject`.
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The *userData* pointer is passed into the hook function. Since hook
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functions may be called from different runtimes, this pointer should not
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refer directly to Python state.
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As this hook is intentionally used during import, avoid importing new modules
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during its execution unless they are known to be frozen or available in
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``sys.modules``.
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Once a hook has been set, it cannot be removed or replaced, and later calls to
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:c:func:`PyFile_SetOpenCodeHook` will fail. On failure, the function returns
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-1 and sets an exception if the interpreter has been initialized.
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This function is safe to call before :c:func:`Py_Initialize`.
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.. versionadded:: 3.8
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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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