cpython/Doc/library/os.path.rst

333 lines
12 KiB
ReStructuredText

: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. 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.
.. 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
* :mod:`macpath` for old-style MacOS paths
.. 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))``.
.. 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 (``''``).
.. 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 element of
the pair returned by passing *path* to the function :func:`split`.
.. 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.
.. 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`.
.. 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.
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.
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.
.. function:: getsize(path)
Return the size, in bytes, of *path*. Raise :exc:`os.error` if the file does
not exist or is inaccessible.
.. 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``) following each non-empty part except the last.
(This means that an empty last part will result in a path that ends with a
separator.) 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 and Mac OS X, 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.
Raise a TypeError if the type of *path* is not ``str`` or ``bytes``.
.. function:: normpath(path)
Normalize a pathname. This collapses redundant separators and up-level
references so that ``A//B``, ``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).
.. function:: relpath(path, start=None)
Return a relative filepath to *path* either from the current directory or from
an optional *start* point.
*start* defaults to :attr:`os.curdir`.
Availability: Unix, Windows.
.. function:: samefile(path1, path2)
Return ``True`` if both pathname arguments refer to the same file or directory.
On Unix, this is determined by the device number and i-node number and raises an
exception if a :func:`os.stat` call on either pathname fails.
On Windows, two files are the same if they resolve to the same final path
name using the Windows API call GetFinalPathNameByHandle. This function
raises an exception if handles cannot be obtained to either file.
Availability: Unix, Windows.
.. versionchanged:: 3.2
Added Windows support.
.. 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.
.. 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
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`.
.. 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")``
.. 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', '')``.
.. function:: splitunc(path)
.. deprecated:: 3.1
Use *splitdrive* instead.
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.
.. data:: supports_unicode_filenames
True if arbitrary Unicode strings can be used as file names (within limitations
imposed by the file system).