mirror of https://github.com/python/cpython
479 lines
16 KiB
ReStructuredText
479 lines
16 KiB
ReStructuredText
:mod:`os.path` --- Common pathname manipulations
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================================================
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.. module:: os.path
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:synopsis: Operations on pathnames.
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**Source code:** :source:`Lib/posixpath.py` (for POSIX) and
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:source:`Lib/ntpath.py` (for Windows NT).
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.. index:: single: path; operations
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--------------
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This module implements some useful functions on pathnames. To read or
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write files see :func:`open`, and for accessing the filesystem see the
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:mod:`os` module. The path parameters can be passed as either strings,
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or bytes. Applications are encouraged to represent file names as
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(Unicode) character strings. Unfortunately, some file names may not be
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representable as strings on Unix, so applications that need to support
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arbitrary file names on Unix should use bytes objects to represent
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path names. Vice versa, using bytes objects cannot represent all file
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names on Windows (in the standard ``mbcs`` encoding), hence Windows
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applications should use string objects to access all files.
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Unlike a unix shell, Python does not do any *automatic* path expansions.
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Functions such as :func:`expanduser` and :func:`expandvars` can be invoked
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explicitly when an application desires shell-like path expansion. (See also
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the :mod:`glob` module.)
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.. seealso::
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The :mod:`pathlib` module offers high-level path objects.
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.. note::
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All of these functions accept either only bytes or only string objects as
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their parameters. The result is an object of the same type, if a path or
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file name is returned.
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.. note::
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Since different operating systems have different path name conventions, there
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are several versions of this module in the standard library. The
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:mod:`os.path` module is always the path module suitable for the operating
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system Python is running on, and therefore usable for local paths. However,
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you can also import and use the individual modules if you want to manipulate
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a path that is *always* in one of the different formats. They all have the
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same interface:
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* :mod:`posixpath` for UNIX-style paths
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* :mod:`ntpath` for Windows paths
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.. versionchanged:: 3.8
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:func:`exists`, :func:`lexists`, :func:`isdir`, :func:`isfile`,
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:func:`islink`, and :func:`ismount` now return ``False`` instead of
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raising an exception for paths that contain characters or bytes
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unrepresentable at the OS level.
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.. function:: abspath(path)
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Return a normalized absolutized version of the pathname *path*. On most
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platforms, this is equivalent to calling the function :func:`normpath` as
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follows: ``normpath(join(os.getcwd(), path))``.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: basename(path)
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Return the base name of pathname *path*. This is the second element of the
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pair returned by passing *path* to the function :func:`split`. Note that
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the result of this function is different
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from the Unix :program:`basename` program; where :program:`basename` for
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``'/foo/bar/'`` returns ``'bar'``, the :func:`basename` function returns an
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empty string (``''``).
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: commonpath(paths)
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Return the longest common sub-path of each pathname in the sequence
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*paths*. Raise :exc:`ValueError` if *paths* contain both absolute
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and relative pathnames, the *paths* are on the different drives or
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if *paths* is empty. Unlike :func:`commonprefix`, this returns a
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valid path.
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.. availability:: Unix, Windows.
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.. versionadded:: 3.5
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.. versionchanged:: 3.6
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Accepts a sequence of :term:`path-like objects <path-like object>`.
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.. function:: commonprefix(list)
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Return the longest path prefix (taken character-by-character) that is a
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prefix of all paths in *list*. If *list* is empty, return the empty string
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(``''``).
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.. note::
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This function may return invalid paths because it works a
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character at a time. To obtain a valid path, see
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:func:`commonpath`.
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::
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>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
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'/usr/l'
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>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
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'/usr'
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: dirname(path)
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Return the directory name of pathname *path*. This is the first element of
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the pair returned by passing *path* to the function :func:`split`.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: exists(path)
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Return ``True`` if *path* refers to an existing path or an open
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file descriptor. Returns ``False`` for broken symbolic links. On
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some platforms, this function may return ``False`` if permission is
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not granted to execute :func:`os.stat` on the requested file, even
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if the *path* physically exists.
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.. versionchanged:: 3.3
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*path* can now be an integer: ``True`` is returned if it is an
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open file descriptor, ``False`` otherwise.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: lexists(path)
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Return ``True`` if *path* refers to an existing path. Returns ``True`` for
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broken symbolic links. Equivalent to :func:`exists` on platforms lacking
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:func:`os.lstat`.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. index:: single: ~ (tilde); home directory expansion
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.. function:: expanduser(path)
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On Unix and Windows, return the argument with an initial component of ``~`` or
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``~user`` replaced by that *user*'s home directory.
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.. index:: module: pwd
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On Unix, an initial ``~`` is replaced by the environment variable :envvar:`HOME`
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if it is set; otherwise the current user's home directory is looked up in the
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password directory through the built-in module :mod:`pwd`. An initial ``~user``
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is looked up directly in the password directory.
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On Windows, :envvar:`USERPROFILE` will be used if set, otherwise a combination
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of :envvar:`HOMEPATH` and :envvar:`HOMEDRIVE` will be used. An initial
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``~user`` is handled by checking that the last directory component of the current
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user's home directory matches :envvar:`USERNAME`, and replacing it if so.
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If the expansion fails or if the path does not begin with a tilde, the path is
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returned unchanged.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. versionchanged:: 3.8
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No longer uses :envvar:`HOME` on Windows.
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.. index::
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single: $ (dollar); environment variables expansion
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single: % (percent); environment variables expansion (Windows)
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.. function:: expandvars(path)
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Return the argument with environment variables expanded. Substrings of the form
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``$name`` or ``${name}`` are replaced by the value of environment variable
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*name*. Malformed variable names and references to non-existing variables are
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left unchanged.
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On Windows, ``%name%`` expansions are supported in addition to ``$name`` and
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``${name}``.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: getatime(path)
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Return the time of last access of *path*. The return value is a floating point number giving
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the number of seconds since the epoch (see the :mod:`time` module). Raise
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:exc:`OSError` if the file does not exist or is inaccessible.
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.. function:: getmtime(path)
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Return the time of last modification of *path*. The return value is a floating point number
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giving the number of seconds since the epoch (see the :mod:`time` module).
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Raise :exc:`OSError` if the file does not exist or is inaccessible.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: getctime(path)
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Return the system's ctime which, on some systems (like Unix) is the time of the
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last metadata change, and, on others (like Windows), is the creation time for *path*.
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The return value is a number giving the number of seconds since the epoch (see
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the :mod:`time` module). Raise :exc:`OSError` if the file does not exist or
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is inaccessible.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: getsize(path)
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Return the size, in bytes, of *path*. Raise :exc:`OSError` if the file does
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not exist or is inaccessible.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: isabs(path)
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Return ``True`` if *path* is an absolute pathname. On Unix, that means it
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begins with a slash, on Windows that it begins with a (back)slash after chopping
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off a potential drive letter.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: isfile(path)
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Return ``True`` if *path* is an :func:`existing <exists>` regular file.
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This follows symbolic links, so both :func:`islink` and :func:`isfile` can
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be true for the same path.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: isdir(path)
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Return ``True`` if *path* is an :func:`existing <exists>` directory. This
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follows symbolic links, so both :func:`islink` and :func:`isdir` can be true
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for the same path.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: islink(path)
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Return ``True`` if *path* refers to an :func:`existing <exists>` directory
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entry that is a symbolic link. Always ``False`` if symbolic links are not
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supported by the Python runtime.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: ismount(path)
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Return ``True`` if pathname *path* is a :dfn:`mount point`: a point in a
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file system where a different file system has been mounted. On POSIX, the
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function checks whether *path*'s parent, :file:`{path}/..`, is on a different
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device than *path*, or whether :file:`{path}/..` and *path* point to the same
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i-node on the same device --- this should detect mount points for all Unix
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and POSIX variants. It is not able to reliably detect bind mounts on the
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same filesystem. On Windows, a drive letter root and a share UNC are
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always mount points, and for any other path ``GetVolumePathName`` is called
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to see if it is different from the input path.
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.. versionadded:: 3.4
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Support for detecting non-root mount points on Windows.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: join(path, *paths)
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Join one or more path components intelligently. The return value is the
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concatenation of *path* and any members of *\*paths* with exactly one
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directory separator following each non-empty part except the last, meaning
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that the result will only end in a separator if the last part is empty. If
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a component is an absolute path, all previous components are thrown away
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and joining continues from the absolute path component.
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On Windows, the drive letter is not reset when an absolute path component
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(e.g., ``r'\foo'``) is encountered. If a component contains a drive
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letter, all previous components are thrown away and the drive letter is
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reset. Note that since there is a current directory for each drive,
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``os.path.join("c:", "foo")`` represents a path relative to the current
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directory on drive :file:`C:` (:file:`c:foo`), not :file:`c:\\foo`.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object` for *path* and *paths*.
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.. function:: normcase(path)
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Normalize the case of a pathname. On Windows, convert all characters in the
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pathname to lowercase, and also convert forward slashes to backward slashes.
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On other operating systems, return the path unchanged.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: normpath(path)
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Normalize a pathname by collapsing redundant separators and up-level
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references so that ``A//B``, ``A/B/``, ``A/./B`` and ``A/foo/../B`` all
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become ``A/B``. This string manipulation may change the meaning of a path
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that contains symbolic links. On Windows, it converts forward slashes to
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backward slashes. To normalize case, use :func:`normcase`.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: realpath(path)
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Return the canonical path of the specified filename, eliminating any symbolic
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links encountered in the path (if they are supported by the operating
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system).
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.. note::
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When symbolic link cycles occur, the returned path will be one member of
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the cycle, but no guarantee is made about which member that will be.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. versionchanged:: 3.8
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Symbolic links and junctions are now resolved on Windows.
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.. function:: relpath(path, start=os.curdir)
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Return a relative filepath to *path* either from the current directory or
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from an optional *start* directory. This is a path computation: the
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filesystem is not accessed to confirm the existence or nature of *path* or
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*start*. On Windows, :exc:`ValueError` is raised when *path* and *start*
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are on different drives.
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*start* defaults to :attr:`os.curdir`.
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.. availability:: Unix, Windows.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: samefile(path1, path2)
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Return ``True`` if both pathname arguments refer to the same file or directory.
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This is determined by the device number and i-node number and raises an
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exception if an :func:`os.stat` call on either pathname fails.
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.. availability:: Unix, Windows.
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.. versionchanged:: 3.2
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Added Windows support.
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.. versionchanged:: 3.4
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Windows now uses the same implementation as all other platforms.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: sameopenfile(fp1, fp2)
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Return ``True`` if the file descriptors *fp1* and *fp2* refer to the same file.
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.. availability:: Unix, Windows.
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.. versionchanged:: 3.2
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Added Windows support.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: samestat(stat1, stat2)
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Return ``True`` if the stat tuples *stat1* and *stat2* refer to the same file.
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These structures may have been returned by :func:`os.fstat`,
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:func:`os.lstat`, or :func:`os.stat`. This function implements the
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underlying comparison used by :func:`samefile` and :func:`sameopenfile`.
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.. availability:: Unix, Windows.
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.. versionchanged:: 3.4
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Added Windows support.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: split(path)
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Split the pathname *path* into a pair, ``(head, tail)`` where *tail* is the
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last pathname component and *head* is everything leading up to that. The
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*tail* part will never contain a slash; if *path* ends in a slash, *tail*
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will be empty. If there is no slash in *path*, *head* will be empty. If
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*path* is empty, both *head* and *tail* are empty. Trailing slashes are
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stripped from *head* unless it is the root (one or more slashes only). In
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all cases, ``join(head, tail)`` returns a path to the same location as *path*
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(but the strings may differ). Also see the functions :func:`dirname` and
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:func:`basename`.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: splitdrive(path)
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Split the pathname *path* into a pair ``(drive, tail)`` where *drive* is either
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a mount point or the empty string. On systems which do not use drive
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specifications, *drive* will always be the empty string. In all cases, ``drive
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+ tail`` will be the same as *path*.
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On Windows, splits a pathname into drive/UNC sharepoint and relative path.
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If the path contains a drive letter, drive will contain everything
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up to and including the colon.
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e.g. ``splitdrive("c:/dir")`` returns ``("c:", "/dir")``
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If the path contains a UNC path, drive will contain the host name
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and share, up to but not including the fourth separator.
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e.g. ``splitdrive("//host/computer/dir")`` returns ``("//host/computer", "/dir")``
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. function:: splitext(path)
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Split the pathname *path* into a pair ``(root, ext)`` such that ``root + ext ==
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path``, and *ext* is empty or begins with a period and contains at most one
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period. Leading periods on the basename are ignored; ``splitext('.cshrc')``
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returns ``('.cshrc', '')``.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. data:: supports_unicode_filenames
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``True`` if arbitrary Unicode strings can be used as file names (within limitations
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imposed by the file system).
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