10%python2.7之os.path

10.1. os.path — Common pathname manipulations

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

這子產品實作一些路徑名的功能、讀寫檔案請看open，通路檔案系統請看os子產品

Note

On Windows, many of these functions do not properly support UNC pathnames.splitunc() andismount() do handle them correctly.

window系統中，許多這樣的功能并不能很好地支援UNC路徑名。splitunc() and ismount()可以解決

Unlike a unix shell, Python does not do any automatic path expansions. Functions such asexpanduser() andexpandvars() can be invoked explicitly when an application desires shell-like path expansion. (See also theglob module.)

不像unix的shell腳本，python不會處理路徑拓展。當某個程式要求類似shell的路徑拓展時，expanduser() and expandvars()可以明确地被涉及到

（注：路徑拓展詳見：http://jjz.iteye.com/blog/388946,這裡我了解為正規表達式,如果不懂，可以去看看下面有個函數叫做os.path.expanduser(path)，肯定能看懂 ）

Note

Since different operating systems have different path name conventions, there are several versions of this module in the standard library. Theos.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

自從不同os有不一樣的路徑名協定，這标準庫有很多版本的子產品來對應使用。os.path子產品總是适用在運作python環境的os（我的是win7），并且是以也适用本地路徑。同時，如果你想操作某個含有不同格式的路徑，你也可以導入并且使用這獨立的子產品。它們都有一樣的接口： os.path. abspath ( path )

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

New in version 1.5.2.

os.path. basename ( path )

Return the base name of pathname path. This is the second element of the pair returned by passingpath to the function split(). Note that the result of this function is different from the Unixbasename 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 inlist. 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 element of the pair returned by passingpath to the function split().

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 returnFalse if permission is not granted to executeos.stat() on the requested file, even if thepath physically exists.

             如果路徑查到是已經存在的路徑，傳回true。對已經損壞（已經被删除）的符号連結（linux下符号連結，類似快捷方式）傳回false。在某些平台，如果權限不夠去執行在被要求的檔案的os.stat（），這功能可能傳回false，即使實體路徑是存在的。

os.path. lexists ( path )

Return True if path refers to an existing path. Returns True for broken symbolic links. Equivalent toexists() on platforms lackingos.lstat().

New in version 2.4.

os.path. expanduser ( path )

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

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

On Windows, HOME andUSERPROFILE will be used if set, otherwise a combination ofHOMEPATH andHOMEDRIVE 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 variablename. 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 thetime module). Raiseos.error if the file does not exist or is inaccessible.

New in version 1.5.2.

Changed in version 2.3: If os.stat_float_times() returnsTrue, 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 thetime module). Raiseos.error if the file does not exist or is inaccessible.

New in version 1.5.2.

Changed in version 2.3: If os.stat_float_times() returnsTrue, 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 metadata change, and, on others (like Windows), is the creation time forpath. The return value is a number giving the number of seconds since the epoch (see thetime module). Raiseos.error if the file does not exist or is inaccessible.

New in version 2.3.

os.path. getsize ( path )

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

New in version 1.5.2.

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() andisfile() 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() andisdir() 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 by the python runtime.

os.path. ismount ( path )

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

os.path. join ( path, *paths )

Join one or more path components intelligently. The return value is the concatenation ofpath 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 C: (c:foo), notc:\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 by collapsing redundant separators and up-level references so thatA//B, A/B/, A/./B andA/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, usenormcase().

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).

New in version 2.2.

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

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

start defaults to os.curdir.

Availability: Windows, Unix.

New in version 2.6.

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 aos.stat() call on either pathname fails.

Availability: Unix.

os.path. sameopenfile ( fp1, fp2 )

Return True if the file descriptorsfp1 and fp2 refer to the same file.

Availability: Unix.

os.path. samestat ( stat1, stat2 )

Return True if the stat tuplesstat1 and stat2 refer to the same file. These structures may have been returned byos.fstat(),os.lstat(), oros.stat(). This function implements the underlying comparison used bysamefile() andsameopenfile().

Availability: Unix.

os.path. split ( path )

Split the pathname path into a pair, (head,tail) where tail is the last pathname component andhead is everything leading up to that. The tail part will never contain a slash; ifpath ends in a slash, tail will be empty. If there is no slash inpath, head will be empty. If path is empty, both head andtail 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 functionsdirname() andbasename().

os.path. 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 aspath.

New in version 1.3.

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', '').

Changed in version 2.6: Earlier versions could produce an empty root when the only period was the first character.

os.path. splitunc ( path )

Split the pathname path into a pair (unc,rest) so that unc is the UNC mount point (such asr'\\host\mount'), if present, andrest 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. walk ( path, visit, arg )

Calls the function visit with arguments (arg, dirname, names) for each directory in the directory tree rooted at path (includingpath itself, if it is a directory). The argument dirname specifies the visited directory, the argumentnames lists the files in the directory (gotten from os.listdir(dirname)). The visit function may modifynames to influence the set of directories visited below dirname, e.g. to avoid visiting certain parts of the tree. (The object referred to bynames must be modified in place, using del or slice assignment.)

Note

Symbolic links to directories are not treated as subdirectories, and thatwalk() therefore will not visit them. To visit linked directories you must identify them withos.path.islink(file) andos.path.isdir(file), and invokewalk() as necessary.

Note

This function is deprecated and has been removed in Python 3 in favor ofos.walk().

os.path. supports_unicode_filenames

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

New in version 2.3.