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# 10.1. `os.path` — Common pathname manipulations

This module implements some useful functions on pathnames. To read or write files see `open()`, and for accessing the filesystem see the `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 `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:

- `posixpath` for UNIX-style paths
- `ntpath` for Windows paths
- `macpath` for old-style MacOS paths
- `os2emxpath` for OS/2 EMX paths

`os.path.``abspath`(path)
  Return a normalized absolutized version of the pathname path. On most platforms, this is equivalent to `normpath(join(os.getcwd(), path))`.

`os.path.``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 basename program; where basename for `'/foo/bar/'` returns `'bar'`, the `basename()` function returns an empty string (`''`).

`os.path.``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.

`os.path.``dirname`(path)
  Return the directory name of pathname path. This is the first half of the pair returned by `split(path)`.

`os.path.``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 `os.stat()` on the requested file, even if the path physically exists.

`os.path.``lexists`(path)
  Return `True` if path refers to an existing path. Returns `True` for broken symbolic links. Equivalent to `exists()` on platforms lacking `os.lstat()`.

`os.path.``expanduser`(path)

  On Unix and Windows, return the argument with an initial component of `~` or `~user` replaced by that user‘s home directory.

  On Unix, an initial `~` is replaced by the environment variable HOME if it is set; otherwise the current user’s home directory is looked up in the password directory through the built-in module `pwd`. An initial `~user` is looked up directly in the password directory.

  On Windows, HOME and USERPROFILE will be used if set, otherwise a combination of HOMEPATH and 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.

`os.path.``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}`.

`os.path.``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 `time` module). Raise `os.error` if the file does not exist or is inaccessible.

  If `os.stat_float_times()` returns True, the result is a floating point number.

`os.path.``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 `time` module). Raise `os.error` if the file does not exist or is inaccessible.

  If `os.stat_float_times()` returns True, the result is a floating point number.

`os.path.``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 `time` module). Raise `os.error` if the file does not exist or is inaccessible.

`os.path.``getsize`(path)
  Return the size, in bytes, of path. Raise `os.error` if the file does not exist or is inaccessible.

`os.path.``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.

`os.path.``isfile`(path)
  Return `True` if path is an existing regular file. This follows symbolic links, so both `islink()` and `isfile()` can be true for the same path.

`os.path.``isdir`(path)
  Return `True` if path is an existing directory. This follows symbolic links, so both `islink()` and `isdir()` can be true for the same path.

`os.path.``islink`(path)
  Return `True` if path refers to a directory entry that is a symbolic link. Always `False` if symbolic links are not supported.

`os.path.``ismount`(path)
  Return `True` if pathname path is a mount point: a point in a file system where a different file system has been mounted. The function checks whether path‘s parent, `path/..`, is on a different device than path, or whether `path/..` and path point to the same i-node on the same device — this should detect mount points for all Unix and POSIX variants.

`os.path.``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 `C:` (`c:foo`), not `c:\foo`.

`os.path.``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.

`os.path.``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 `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!

`os.path.``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).

`os.path.``relpath`(path[, start])

  Return a relative filepath to path either from the current directory or from an optional start point.

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

`os.path.``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 `os.stat()` call on either pathname fails. Availability: Unix.

`os.path.``sameopenfile`(fp1, fp2)
  Return `True` if the file descriptors fp1 and fp2 refer to the same file. Availability: Unix.

`os.path.``samestat`(stat1, stat2)
  Return `True` if the stat tuples stat1 and stat2 refer to the same file. These structures may have been returned by `fstat()`, `lstat()`, or `stat()`. This function implements the underlying comparison used by `samefile()` and `sameopenfile()`. Availability: Unix.

`os.path.``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).

`os.path.``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")`

`os.path.``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', '')`.

`os.path.``splitunc`(path)

  Deprecated since version 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.

`os.path.``supports_unicode_filenames`
  True if arbitrary Unicode strings can be used as file names (within limitations imposed by the file system), and if `os.listdir()` returns strings that contain characters that cannot be represented by ASCII.

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