path: root/Doc/library/os.path.rst

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

.. module:: os.path
   :synopsis: Operations on pathnames.

**Source code:** :source:`Lib/posixpath.py` (for POSIX) and
:source:`Lib/ntpath.py` (for Windows NT).

.. 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. The path parameters can be passed as either strings,
or bytes. Applications are encouraged to represent file names as
(Unicode) character strings. Unfortunately, some file names may not be
representable as strings on Unix, so applications that need to support
arbitrary file names on Unix should use bytes objects to represent
path names. Vice versa, using bytes objects cannot represent all file
names on Windows (in the standard ``mbcs`` encoding), hence Windows
applications should use string objects to access all files.

Unlike a unix shell, Python does not do any *automatic* path expansions.
Functions such as :func:`expanduser` and :func:`expandvars` can be invoked
explicitly when an application desires shell-like path expansion.  (See also
the :mod:`glob` module.)


.. seealso::
   The :mod:`pathlib` module offers high-level path objects.


.. note::

   All of these functions accept either only bytes or only string objects as
   their parameters.  The result is an object of the same type, if a path or
   file name is returned.


.. note::

   Since different operating systems have different path name conventions, there
   are several versions of this module in the standard library.  The
   :mod:`os.path` module is always the path module suitable for the operating
   system Python is running on, and therefore usable for local paths.  However,
   you can also import and use the individual modules if you want to manipulate
   a path that is *always* in one of the different formats.  They all have the
   same interface:

   * :mod:`posixpath` for UNIX-style paths
   * :mod:`ntpath` for Windows paths


.. versionchanged:: 3.8

   :func:`exists`, :func:`lexists`, :func:`isdir`, :func:`isfile`,
   :func:`islink`, and :func:`ismount` now return ``False`` instead of
   raising an exception for paths that contain characters or bytes
   unrepresentable at the OS level.


.. function:: abspath(path)

   Return a normalized absolutized version of the pathname *path*. On most
   platforms, this is equivalent to calling the function :func:`normpath` as
   follows: ``normpath(join(os.getcwd(), path))``.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: basename(path)

   Return the base name of pathname *path*.  This is the second element of the
   pair returned by passing *path* to the function :func:`split`.  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 (``''``).

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: commonpath(paths)

   Return the longest common sub-path of each pathname in the sequence
   *paths*.  Raise :exc:`ValueError` if *paths* contain both absolute
   and relative pathnames, the *paths* are on the different drives or
   if *paths* is empty.  Unlike :func:`commonprefix`, this returns a
   valid path.

   .. availability:: Unix, Windows.

   .. versionadded:: 3.5

   .. versionchanged:: 3.6
      Accepts a sequence of :term:`path-like objects <path-like object>`.


.. 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::

      This function may return invalid paths because it works a
      character at a time.  To obtain a valid path, see
      :func:`commonpath`.

      ::

        >>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
        '/usr/l'

        >>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
        '/usr'

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: dirname(path)

   Return the directory name of pathname *path*.  This is the first element of
   the pair returned by passing *path* to the function :func:`split`.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: exists(path)

   Return ``True`` if *path* refers to an existing path or an open
   file descriptor.  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.

   .. versionchanged:: 3.3
      *path* can now be an integer: ``True`` is returned if it is an
       open file descriptor, ``False`` otherwise.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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`.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. index:: single: ~ (tilde); home directory expansion

.. 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:`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.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.

   .. versionchanged:: 3.8
      No longer uses :envvar:`HOME` on Windows.

.. index::
   single: $ (dollar); environment variables expansion
   single: % (percent); environment variables expansion (Windows)

.. 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}``.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: getatime(path)

   Return the time of last access of *path*.  The return value is a floating point number giving
   the number of seconds since the epoch (see the  :mod:`time` module).  Raise
   :exc:`OSError` if the file does not exist or is inaccessible.


.. function:: getmtime(path)

   Return the time of last modification of *path*.  The return value is a floating point number
   giving the number of seconds since the epoch (see the  :mod:`time` module).
   Raise :exc:`OSError` if the file does not exist or is inaccessible.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: getctime(path)

   Return the system's ctime which, on some systems (like Unix) is the time of the
   last metadata 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:`OSError` if the file does not exist or
   is inaccessible.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: getsize(path)

   Return the size, in bytes, of *path*.  Raise :exc:`OSError` if the file does
   not exist or is inaccessible.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: isfile(path)

   Return ``True`` if *path* is an :func:`existing <exists>` regular file.
   This follows symbolic links, so both :func:`islink` and :func:`isfile` can
   be true for the same path.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: isdir(path)

   Return ``True`` if *path* is an :func:`existing <exists>` directory.  This
   follows symbolic links, so both :func:`islink` and :func:`isdir` can be true
   for the same path.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: islink(path)

   Return ``True`` if *path* refers to an :func:`existing <exists>` directory
   entry that is a symbolic link.  Always ``False`` if symbolic links are not
   supported by the Python runtime.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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.  On POSIX, 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.  It is not able to reliably detect bind mounts on the
   same filesystem.  On Windows, a drive letter root and a share UNC are
   always mount points, and for any other path ``GetVolumePathName`` is called
   to see if it is different from the input path.

   .. versionadded:: 3.4
      Support for detecting non-root mount points on Windows.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: join(path, *paths)

   Join one or more path components intelligently.  The return value is the
   concatenation of *path* and any members of *\*paths* with exactly one
   directory separator (``os.sep``) following each non-empty part except the
   last, meaning that the result will only end in a separator if the last
   part is empty.  If a component is an absolute path, all previous
   components are thrown away and joining continues from the absolute path
   component.

   On Windows, the drive letter is not reset when an absolute path component
   (e.g., ``r'\foo'``) is encountered.  If a component contains a drive
   letter, all previous components are thrown away and the drive letter is
   reset.  Note that 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`.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object` for *path* and *paths*.


.. function:: normcase(path)

   Normalize the case of a pathname.  On Windows, convert all characters in the
   pathname to lowercase, and also convert forward slashes to backward slashes.
   On other operating systems, return the path unchanged.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: normpath(path)

   Normalize a pathname by collapsing redundant separators and up-level
   references so that ``A//B``, ``A/B/``, ``A/./B`` and ``A/foo/../B`` all
   become ``A/B``.  This string manipulation may change the meaning of a path
   that contains symbolic links.  On Windows, it converts forward slashes to
   backward slashes. To normalize case, use :func:`normcase`.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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).

   .. note::
      When symbolic link cycles occur, the returned path will be one member of
      the cycle, but no guarantee is made about which member that will be.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.

   .. versionchanged:: 3.8
      Symbolic links and junctions are now resolved on Windows.


.. function:: relpath(path, start=os.curdir)

   Return a relative filepath to *path* either from the current directory or
   from an optional *start* directory.  This is a path computation:  the
   filesystem is not accessed to confirm the existence or nature of *path* or
   *start*.

   *start* defaults to :attr:`os.curdir`.

   .. availability:: Unix, Windows.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: samefile(path1, path2)

   Return ``True`` if both pathname arguments refer to the same file or directory.
   This is determined by the device number and i-node number and raises an
   exception if an :func:`os.stat` call on either pathname fails.

   .. availability:: Unix, Windows.

   .. versionchanged:: 3.2
      Added Windows support.

   .. versionchanged:: 3.4
      Windows now uses the same implementation as all other platforms.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: sameopenfile(fp1, fp2)

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

   .. availability:: Unix, Windows.

   .. versionchanged:: 3.2
      Added Windows support.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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:`os.fstat`,
   :func:`os.lstat`, or :func:`os.stat`.  This function implements the
   underlying comparison used by :func:`samefile` and :func:`sameopenfile`.

   .. availability:: Unix, Windows.

   .. versionchanged:: 3.4
      Added Windows support.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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
   all cases, ``join(head, tail)`` returns a path to the same location as *path*
   (but the strings may differ).  Also see the functions :func:`dirname` and
   :func:`basename`.

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. function:: splitdrive(path)

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

   On Windows, splits a pathname into drive/UNC sharepoint and relative path.

   If the path contains a drive letter, drive will contain everything
   up to and including the colon.
   e.g. ``splitdrive("c:/dir")`` returns ``("c:", "/dir")``

   If the path contains a UNC path, drive will contain the host name
   and share, up to but not including the fourth separator.
   e.g. ``splitdrive("//host/computer/dir")`` returns ``("//host/computer", "/dir")``

   .. versionchanged:: 3.6
      Accepts a :term:`path-like object`.


.. 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:: 3.6
      Accepts a :term:`path-like object`.


.. data:: supports_unicode_filenames

   ``True`` if arbitrary Unicode strings can be used as file names (within limitations
   imposed by the file system).