mirror of https://github.com/python/cpython
282 lines
11 KiB
ReStructuredText
282 lines
11 KiB
ReStructuredText
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: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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.. index:: single: path; operations
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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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.. 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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.. warning::
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On Windows, many of these functions do not properly support UNC pathnames.
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:func:`splitunc` and :func:`ismount` do handle them correctly.
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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 ``normpath(join(os.getcwd(), path))``.
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.. function:: basename(path)
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Return the base name of pathname *path*. This is the second half of the pair
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returned by ``split(path)``. Note that 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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.. function:: commonprefix(list)
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Return the longest path prefix (taken character-by-character) that is a prefix
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of all paths in *list*. If *list* is empty, return the empty string (``''``).
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Note that this may return invalid paths because it works a character at a time.
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.. function:: dirname(path)
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Return the directory name of pathname *path*. This is the first half of the
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pair returned by ``split(path)``.
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.. function:: exists(path)
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Return ``True`` if *path* refers to an existing path. Returns ``False`` for
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broken symbolic links. On some platforms, this function may return ``False`` if
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permission is 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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.. 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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.. 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:`HOME` and :envvar:`USERPROFILE` will be used if set,
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otherwise a combination of :envvar:`HOMEPATH` and :envvar:`HOMEDRIVE` will be
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used. An initial ``~user`` is handled by stripping the last directory component
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from the created user path derived above.
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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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.. 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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.. function:: getatime(path)
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Return the time of last access of *path*. The return value is a number giving
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the number of seconds since the epoch (see the :mod:`time` module). Raise
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:exc:`os.error` if the file does not exist or is inaccessible.
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If :func:`os.stat_float_times` returns True, the result is a floating point
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number.
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.. function:: getmtime(path)
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Return the time of last modification of *path*. The return value is a number
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giving the number of seconds since the epoch (see the :mod:`time` module).
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Raise :exc:`os.error` if the file does not exist or is inaccessible.
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If :func:`os.stat_float_times` returns True, the result is a floating point
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number.
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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 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:`os.error` if the file does not exist or
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is inaccessible.
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.. function:: getsize(path)
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Return the size, in bytes, of *path*. Raise :exc:`os.error` if the file does
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not exist or is inaccessible.
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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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.. function:: isfile(path)
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Return ``True`` if *path* is an existing regular file. This follows symbolic
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links, so both :func:`islink` and :func:`isfile` can be true for the same path.
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.. function:: isdir(path)
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Return ``True`` if *path* is an existing directory. This follows symbolic
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links, so both :func:`islink` and :func:`isdir` can be true for the same path.
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.. function:: islink(path)
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Return ``True`` if *path* refers to a directory entry that is a symbolic link.
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Always ``False`` if symbolic links are not supported.
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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 file
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system where a different file system has been mounted. The function checks
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whether *path*'s parent, :file:`path/..`, is on a different device than *path*,
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or whether :file:`path/..` and *path* point to the same i-node on the same
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device --- this should detect mount points for all Unix and POSIX variants.
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.. function:: join(path1[, path2[, ...]])
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Join one or more path components intelligently. If any component is an absolute
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path, all previous components (on Windows, including the previous drive letter,
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if there was one) are thrown away, and joining continues. The return value is
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the concatenation of *path1*, and optionally *path2*, etc., with exactly one
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directory separator (``os.sep``) inserted between components, unless *path2* is
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empty. Note that on Windows, 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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.. function:: normcase(path)
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Normalize the case of a pathname. On Unix and MacOSX, this returns the path unchanged; on
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case-insensitive filesystems, it converts the path to lowercase. On Windows, it
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also converts forward slashes to backward slashes.
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.. function:: normpath(path)
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Normalize a pathname. This collapses redundant separators and up-level
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references so that ``A//B``, ``A/./B`` and ``A/foo/../B`` all become ``A/B``.
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It does not normalize the case (use :func:`normcase` for that). On Windows, it
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converts forward slashes to backward slashes. It should be understood that this
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may change the meaning of the path if it contains symbolic links!
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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 system).
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.. function:: relpath(path[, start])
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Return a relative filepath to *path* either from the current directory or from
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an optional *start* point.
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*start* defaults to :attr:`os.curdir`. Availability: Windows, Unix.
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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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(as indicated by device number and i-node number). Raise an exception if a
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:func:`os.stat` call on either pathname fails. Availability: Unix.
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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.
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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:`fstat`, :func:`lstat`, or
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:func:`stat`. This function implements the underlying comparison used by
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:func:`samefile` and :func:`sameopenfile`. Availability: Unix.
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.. function:: split(path)
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Split the pathname *path* into a pair, ``(head, tail)`` where *tail* is the last
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pathname component and *head* is everything leading up to that. The *tail* part
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will never contain a slash; if *path* ends in a slash, *tail* will be empty. If
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there is no slash in *path*, *head* will be empty. If *path* is empty, both
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*head* and *tail* are empty. Trailing slashes are stripped from *head* unless
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it is the root (one or more slashes only). In nearly all cases, ``join(head,
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tail)`` equals *path* (the only exception being when there were multiple slashes
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separating *head* from *tail*).
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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 drive specification 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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.. 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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.. function:: splitunc(path)
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Split the pathname *path* into a pair ``(unc, rest)`` so that *unc* is the UNC
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mount point (such as ``r'\\host\mount'``), if present, and *rest* the rest of
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the path (such as ``r'\path\file.ext'``). For paths containing drive letters,
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*unc* will always be the empty string. Availability: Windows.
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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), and if :func:`os.listdir` returns strings that
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contain characters that cannot be represented by ASCII.
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