cpython/Doc/library/os.path.rst

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: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))``.
.. 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`.
.. 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.
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.. 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.
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.. 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)
Merged revisions 60284-60349 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r60286 | christian.heimes | 2008-01-25 15:54:23 +0100 (Fri, 25 Jan 2008) | 1 line setup.py doesn't pick up changes to a header file ........ r60287 | christian.heimes | 2008-01-25 16:52:11 +0100 (Fri, 25 Jan 2008) | 2 lines Added the Python core headers Include/*.h and pyconfig.h as dependencies for the extensions in Modules/ It forces a rebuild of all extensions when a header files has been modified ........ r60291 | raymond.hettinger | 2008-01-25 20:24:46 +0100 (Fri, 25 Jan 2008) | 4 lines Changes 54857 and 54840 broke code and were reverted in Py2.5 just before it was released, but that reversion never made it to the Py2.6 head. ........ r60296 | guido.van.rossum | 2008-01-25 20:50:26 +0100 (Fri, 25 Jan 2008) | 2 lines Rewrite the list_inline_repeat overflow check slightly differently. ........ r60301 | thomas.wouters | 2008-01-25 22:09:34 +0100 (Fri, 25 Jan 2008) | 4 lines Use the right (portable) definition of the max of a Py_ssize_t. ........ r60303 | thomas.wouters | 2008-01-26 02:47:05 +0100 (Sat, 26 Jan 2008) | 5 lines Make 'testall' work again when building in a separate directory. test_distutils still fails when doing that. ........ r60305 | neal.norwitz | 2008-01-26 06:54:48 +0100 (Sat, 26 Jan 2008) | 3 lines Prevent this test from failing if there are transient network problems by retrying the host for up to 3 times. ........ r60306 | neal.norwitz | 2008-01-26 08:26:12 +0100 (Sat, 26 Jan 2008) | 12 lines Use a condition variable (threading.Event) rather than sleeps and checking a global to determine when the server is ready to be used. This slows the test down, but should make it correct. There was a race condition before where the server could have assigned a port, yet it wasn't ready to serve requests. If the client sent a request before the server was completely ready, it would get an exception. There was machinery to try to handle this condition. All of that should be unnecessary and removed if this change works. A NOTE was added as a comment about what needs to be fixed. The buildbots will tell us if there are more errors or if this test is now stable. ........ r60307 | neal.norwitz | 2008-01-26 08:38:03 +0100 (Sat, 26 Jan 2008) | 3 lines Fix exception in tearDown on ppc buildbot. If there's no directory, that shouldn't cause the test to fail. Just like it setUp. ........ r60308 | raymond.hettinger | 2008-01-26 09:19:06 +0100 (Sat, 26 Jan 2008) | 3 lines Make PySet_Add() work with frozensets. Works like PyTuple_SetItem() to build-up values in a brand new frozenset. ........ r60309 | neal.norwitz | 2008-01-26 09:26:00 +0100 (Sat, 26 Jan 2008) | 1 line The OS X buildbot had errors with the unavailable exceptions disabled. Restore it. ........ r60310 | raymond.hettinger | 2008-01-26 09:37:28 +0100 (Sat, 26 Jan 2008) | 4 lines Let marshal build-up sets and frozensets one element at a time. Saves the unnecessary creation of a tuple as intermediate container. ........ r60311 | raymond.hettinger | 2008-01-26 09:41:13 +0100 (Sat, 26 Jan 2008) | 1 line Update test code for change to PySet_Add(). ........ r60312 | raymond.hettinger | 2008-01-26 10:31:11 +0100 (Sat, 26 Jan 2008) | 1 line Revert PySet_Add() changes. ........ r60314 | georg.brandl | 2008-01-26 10:43:35 +0100 (Sat, 26 Jan 2008) | 2 lines #1934: fix os.path.isabs docs. ........ r60316 | georg.brandl | 2008-01-26 12:00:18 +0100 (Sat, 26 Jan 2008) | 2 lines Add missing things in re docstring. ........ r60317 | georg.brandl | 2008-01-26 12:02:22 +0100 (Sat, 26 Jan 2008) | 2 lines Slashes allowed on Windows. ........ r60319 | georg.brandl | 2008-01-26 14:41:21 +0100 (Sat, 26 Jan 2008) | 2 lines Fix markup again. ........ r60320 | andrew.kuchling | 2008-01-26 14:50:51 +0100 (Sat, 26 Jan 2008) | 1 line Add some items ........ r60321 | georg.brandl | 2008-01-26 15:02:38 +0100 (Sat, 26 Jan 2008) | 2 lines Clarify "b" mode under Unix. ........ r60322 | georg.brandl | 2008-01-26 15:03:47 +0100 (Sat, 26 Jan 2008) | 3 lines #1940: make it possible to use curses.filter() before curses.initscr() as the documentation says. ........ r60324 | georg.brandl | 2008-01-26 15:14:20 +0100 (Sat, 26 Jan 2008) | 3 lines #1473257: add generator.gi_code attribute that refers to the original code object backing the generator. Patch by Collin Winter. ........ r60325 | georg.brandl | 2008-01-26 15:19:22 +0100 (Sat, 26 Jan 2008) | 2 lines Move C API entries to the corresponding section. ........ r60326 | christian.heimes | 2008-01-26 17:43:35 +0100 (Sat, 26 Jan 2008) | 1 line Unit test fix from Giampaolo Rodola, #1938 ........ r60327 | gregory.p.smith | 2008-01-26 19:51:05 +0100 (Sat, 26 Jan 2008) | 2 lines Update docs for new callpack params added in r60188 ........ r60329 | neal.norwitz | 2008-01-26 21:24:36 +0100 (Sat, 26 Jan 2008) | 3 lines Cleanup the code a bit. test_rfind is failing on PPC and PPC64 buildbots, this might fix the problem. ........ r60330 | neal.norwitz | 2008-01-26 22:02:45 +0100 (Sat, 26 Jan 2008) | 1 line Always try to remove the test file even if close raises an exception ........ r60331 | neal.norwitz | 2008-01-26 22:21:59 +0100 (Sat, 26 Jan 2008) | 3 lines Reduce the race condition by signalling when the server is ready and not trying to connect before. ........ r60334 | neal.norwitz | 2008-01-27 00:13:46 +0100 (Sun, 27 Jan 2008) | 5 lines On some systems (e.g., Ubuntu on hppa) the flush() doesn't cause the exception, but the close() does. Will backport. ........ r60335 | neal.norwitz | 2008-01-27 00:14:17 +0100 (Sun, 27 Jan 2008) | 2 lines Consistently use tempfile.tempdir for the db_home directory. ........ r60338 | neal.norwitz | 2008-01-27 02:44:05 +0100 (Sun, 27 Jan 2008) | 4 lines Eliminate the sleeps that assume the server will start in .5 seconds. This should make the test less flaky. It also speeds up the test by about 75% on my box (20+ seconds -> ~4 seconds). ........ r60342 | neal.norwitz | 2008-01-27 06:02:34 +0100 (Sun, 27 Jan 2008) | 6 lines Try to prevent this test from being flaky. We might need a sleep in here which isn't as bad as it sounds. The close() *should* raise an exception, so if it didn't we should give more time to sync and really raise it. Will backport. ........ r60344 | jeffrey.yasskin | 2008-01-27 06:40:35 +0100 (Sun, 27 Jan 2008) | 3 lines Make rational.gcd() public and allow Rational to take decimal strings, per Raymond's advice. ........ r60345 | neal.norwitz | 2008-01-27 08:36:03 +0100 (Sun, 27 Jan 2008) | 3 lines Mostly reformat. Also set an error and return NULL if neither MS_WINDOWS nor UNIX is defined. This may have caused problems on cygwin. ........ r60346 | neal.norwitz | 2008-01-27 08:37:38 +0100 (Sun, 27 Jan 2008) | 3 lines Use int for the sign rather than a char. char can be signed or unsigned. It's system dependent. This might fix the problem with test_rfind failing. ........ r60347 | neal.norwitz | 2008-01-27 08:41:33 +0100 (Sun, 27 Jan 2008) | 1 line Add stdarg include for va_list to get this to compile on cygwin ........ r60348 | raymond.hettinger | 2008-01-27 11:13:57 +0100 (Sun, 27 Jan 2008) | 1 line Docstring nit ........ r60349 | raymond.hettinger | 2008-01-27 11:47:55 +0100 (Sun, 27 Jan 2008) | 1 line Removed an unnecessary and confusing paragraph from the namedtuple docs. ........
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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.
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.. 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).
.. 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.
.. 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: Macintosh, Unix.
.. function:: sameopenfile(fp1, fp2)
Return ``True`` if the file descriptors *fp1* and *fp2* refer to the same file.
Availability: Macintosh, 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: Macintosh, 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*.
.. 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)
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), and if :func:`os.listdir` returns strings that
contain characters that cannot be represented by ASCII.