:mod:`os.path` --- Common pathname manipulations

================================================

.. module:: os.path

   :synopsis: Operations on pathnames.

.. index:: single: path; operations

This module implements some useful functions on pathnames. To read or

write files see :func:`open`, and for accessing the filesystem see the

:mod:`os` module.

.. warning::

   On Windows, many of these functions do not properly support UNC pathnames.

   :func:`splitunc` and :func:`ismount` do handle them correctly.

.. function:: abspath(path)

   Return a normalized absolutized version of the pathname *path*. On most

   platforms, this is equivalent to ``normpath(join(os.getcwd(), path))``.

   .. versionadded:: 1.5.2

.. function:: basename(path)

   Return the base name of pathname *path*.  This is the second half of the pair

   returned by ``split(path)``.  Note that the result of this function is different

   from the Unix :program:`basename` program; where :program:`basename` for

   ``'/foo/bar/'`` returns ``'bar'``, the :func:`basename` function returns an

   empty string (``''``).

.. function:: commonprefix(list)

   Return the longest path prefix (taken character-by-character) that is a prefix

   of all paths in  *list*.  If *list* is empty, return the empty string (``''``).

   Note that this may return invalid paths because it works a character at a time.

.. function:: dirname(path)

   Return the directory name of pathname *path*.  This is the first half of the

   pair returned by ``split(path)``.

.. function:: exists(path)

   Return ``True`` if *path* refers to an existing path.  Returns ``False`` for

   broken symbolic links. On some platforms, this function may return ``False`` if

   permission is not granted to execute :func:`os.stat` on the requested file, even

   if the *path* physically exists.

.. function:: lexists(path)

   Return ``True`` if *path* refers to an existing path. Returns ``True`` for

   broken symbolic links.   Equivalent to :func:`exists` on platforms lacking

   :func:`os.lstat`.

   .. versionadded:: 2.4

.. function:: expanduser(path)

   On Unix and Windows, return the argument with an initial component of ``~`` or

   ``~user`` replaced by that *user*'s home directory.

   .. index:: module: pwd

   On Unix, an initial ``~`` is replaced by the environment variable :envvar:`HOME`

   if it is set; otherwise the current user's home directory is looked up in the

   password directory through the built-in module :mod:`pwd`. An initial ``~user``

   is looked up directly in the password directory.

   On Windows, :envvar:`HOME` and :envvar:`USERPROFILE` will be used if set,

   otherwise a combination of :envvar:`HOMEPATH` and :envvar:`HOMEDRIVE` will be

   used.  An initial ``~user`` is handled by stripping the last directory component

   from the created user path derived above.

   If the expansion fails or if the path does not begin with a tilde, the path is

   returned unchanged.

.. function:: expandvars(path)

   Return the argument with environment variables expanded.  Substrings of the form

   ``$name`` or ``${name}`` are replaced by the value of environment variable

   *name*.  Malformed variable names and references to non-existing variables are

   left unchanged.

   On Windows, ``%name%`` expansions are supported in addition to ``$name`` and

   ``${name}``.

.. function:: getatime(path)

   Return the time of last access of *path*.  The return value is a number giving

   the number of seconds since the epoch (see the  :mod:`time` module).  Raise

   :exc:`os.error` if the file does not exist or is inaccessible.

   .. versionadded:: 1.5.2

   .. versionchanged:: 2.3

      If :func:`os.stat_float_times` returns True, the result is a floating point

      number.

.. function:: getmtime(path)

   Return the time of last modification of *path*.  The return value is a number

   giving the number of seconds since the epoch (see the  :mod:`time` module).

   Raise :exc:`os.error` if the file does not exist or is inaccessible.

   .. versionadded:: 1.5.2

   .. versionchanged:: 2.3

      If :func:`os.stat_float_times` returns True, the result is a floating point

      number.

.. function:: getctime(path)

   Return the system's ctime which, on some systems (like Unix) is the time of the

   last change, and, on others (like Windows), is the creation time for *path*.

   The return value is a number giving the number of seconds since the epoch (see

   the  :mod:`time` module).  Raise :exc:`os.error` if the file does not exist or

   is inaccessible.

   .. versionadded:: 2.3

.. function:: getsize(path)

   Return the size, in bytes, of *path*.  Raise :exc:`os.error` if the file does

   not exist or is inaccessible.

   .. versionadded:: 1.5.2

.. function:: isabs(path)

   Return ``True`` if *path* is an absolute pathname.  On Unix, that means it

   begins with a slash, on Windows that it begins with a (back)slash after chopping

   off a potential drive letter.

.. function:: isfile(path)

   Return ``True`` if *path* is an existing regular file.  This follows symbolic

   links, so both :func:`islink` and :func:`isfile` can be true for the same path.

.. function:: isdir(path)

   Return ``True`` if *path* is an existing directory.  This follows symbolic

   links, so both :func:`islink` and :func:`isdir` can be true for the same path.

.. function:: islink(path)

   Return ``True`` if *path* refers to a directory entry that is a symbolic link.

   Always ``False`` if symbolic links are not supported.

.. function:: ismount(path)

   Return ``True`` if pathname *path* is a :dfn:`mount point`: a point in a file

   system where a different file system has been mounted.  The function checks

   whether *path*'s parent, :file:`path/..`, is on a different device than *path*,

   or whether :file:`path/..` and *path* point to the same i-node on the same

   device --- this should detect mount points for all Unix and POSIX variants.

.. function:: join(path1[, path2[, ...]])

   Join one or more path components intelligently.  If any component is an absolute

   path, all previous components (on Windows, including the previous drive letter,

   if there was one) are thrown away, and joining continues.  The return value is

   the concatenation of *path1*, and optionally *path2*, etc., with exactly one

   directory separator (``os.sep``) inserted between components, unless *path2* is

   empty.  Note that on Windows, since there is a current directory for each drive,

   ``os.path.join("c:", "foo")`` represents a path relative to the current

   directory on drive :file:`C:` (:file:`c:foo`), not :file:`c:\\foo`.

.. function:: normcase(path)

   Normalize the case of a pathname.  On Unix, this returns the path unchanged; on

   case-insensitive filesystems, it converts the path to lowercase.  On Windows, it

   also converts forward slashes to backward slashes.

.. function:: normpath(path)

   Normalize a pathname.  This collapses redundant separators and up-level

   references so that ``A//B``, ``A/./B`` and ``A/foo/../B`` all become ``A/B``.

   It does not normalize the case (use :func:`normcase` for that).  On Windows, it

   converts forward slashes to backward slashes. It should be understood that this

   may change the meaning of the path if it contains symbolic links!

.. function:: realpath(path)

   Return the canonical path of the specified filename, eliminating any symbolic

   links encountered in the path (if they are supported by the operating system).

   .. versionadded:: 2.2

.. function:: relpath(path[, start])

   Return a relative filepath to *path* either from the current directory or from

   an optional *start* point.

   *start* defaults to :attr:`os.curdir`. Availability:  Windows, Unix.

   .. versionadded:: 2.6

.. function:: samefile(path1, path2)

   Return ``True`` if both pathname arguments refer to the same file or directory

   (as indicated by device number and i-node number). Raise an exception if a

   :func:`os.stat` call on either pathname fails. Availability: Unix.

.. function:: sameopenfile(fp1, fp2)

   Return ``True`` if the file descriptors *fp1* and *fp2* refer to the same file.

   Availability: Unix.

.. function:: samestat(stat1, stat2)

   Return ``True`` if the stat tuples *stat1* and *stat2* refer to the same file.

   These structures may have been returned by :func:`fstat`, :func:`lstat`, or

   :func:`stat`.  This function implements the underlying comparison used by

   :func:`samefile` and :func:`sameopenfile`. Availability: Unix.

.. function:: split(path)

   Split the pathname *path* into a pair, ``(head, tail)`` where *tail* is the last

   pathname component and *head* is everything leading up to that.  The *tail* part

   will never contain a slash; if *path* ends in a slash, *tail* will be empty.  If

   there is no slash in *path*, *head* will be empty.  If *path* is empty, both

   *head* and *tail* are empty.  Trailing slashes are stripped from *head* unless

   it is the root (one or more slashes only).  In nearly all cases, ``join(head,

   tail)`` equals *path* (the only exception being when there were multiple slashes

   separating *head* from *tail*).

.. function:: splitdrive(path)

   Split the pathname *path* into a pair ``(drive, tail)`` where *drive* is either

   a drive specification or the empty string.  On systems which do not use drive

   specifications, *drive* will always be the empty string.  In all cases, ``drive

   + tail`` will be the same as *path*.

   .. versionadded:: 1.3

.. function:: splitext(path)

   Split the pathname *path* into a pair ``(root, ext)``  such that ``root + ext ==

   path``, and *ext* is empty or begins with a period and contains at most one

   period. Leading periods on the basename are  ignored; ``splitext('.cshrc')``

   returns  ``('.cshrc', '')``.

   .. versionchanged:: 2.6

      Earlier versions could produce an empty root when the only period was the

      first character.

.. function:: splitunc(path)

   Split the pathname *path* into a pair ``(unc, rest)`` so that *unc* is the UNC

   mount point (such as ``r'\\host\mount'``), if present, and *rest* the rest of

   the path (such as  ``r'\path\file.ext'``).  For paths containing drive letters,

   *unc* will always be the empty string. Availability:  Windows.

.. function:: walk(path, visit, arg)

   Calls the function *visit* with arguments ``(arg, dirname, names)`` for each

   directory in the directory tree rooted at *path* (including *path* itself, if it

   is a directory).  The argument *dirname* specifies the visited directory, the

   argument *names* lists the files in the directory (gotten from

   ``os.listdir(dirname)``). The *visit* function may modify *names* to influence

   the set of directories visited below *dirname*, e.g. to avoid visiting certain

   parts of the tree.  (The object referred to by *names* must be modified in

   place, using :keyword:`del` or slice assignment.)

   .. note::

      Symbolic links to directories are not treated as subdirectories, and that

      :func:`walk` therefore will not visit them. To visit linked directories you must

      identify them with ``os.path.islink(file)`` and ``os.path.isdir(file)``, and

      invoke :func:`walk` as necessary.

   .. warning::

      This function is deprecated and has been removed in 3.0 in favor of

      :func:`os.walk`.

.. data:: supports_unicode_filenames

   True if arbitrary Unicode strings can be used as file names (within limitations

   imposed by the file system), and if :func:`os.listdir` returns Unicode strings

   for a Unicode argument.

   .. versionadded:: 2.3