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This module implements some useful functions on pathnames.To read or write files see open(), and for accessing the filesystem see the os module.
Note
On Windows, many of these functions do not properly support UNC pathnames.splitunc() and ismount() do handle them correctly.
Unlike a unix shell, Python does not do any automatic path expansions.Functions such as expanduser() and expandvars() can be invoked explicitly when an application desires shell-like path expansion.(See also the glob module.)
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:
Return a normalized absolutized version of the pathname path.On most platforms, this is equivalent to calling the function normpath() as follows: normpath(join(os.getcwd(), path)).
New in version 1.5.2.
Return the base name of pathname path.This is the second element of the pair returned by passing path to the function split().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 (').
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.
Return the directory name of pathname path.This is the first element of the pair returned by passing path to the function split().
如果path引用一个存在的路径，返回True。如果path引用一个断开的符号链接，返回False。在某些平台上，尽管path物理存在，但是由于没有执行os.stat()的权限，该函数也会返回False。
如果path引用一个存在的路径，返回True。对于断开的符号链接也返回True。Equivalent to exists() on platforms lacking os.lstat().
New in version 2.4.
在Unix和Windows平台上，返回参数，参数中开头的~或者~user被替换成user的主／家目录。
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.
Return the argument with environment variables expanded.参数中形如$name或者${name}的部分被替换成环境变量name的值。Malformed variable names and references to non-existing variables are left unchanged.
On Windows, %name% expansions are supported in addition to $name and ${name}.
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.
New in version 1.5.2.
Changed in version 2.3:If os.stat_float_times() returns True, the result is a floating point number.
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.
New in version 1.5.2.
Changed in version 2.3:If os.stat_float_times() returns True, the result is a floating point number.
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 time module).Raise os.error if the file does not exist or is inaccessible.
New in version 2.3.
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.
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.
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.
Return True if path is an existing directory.This follows symbolic links, so both islink() and isdir() can be true for the same 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.
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.
将一个或多个路径正确地连接起来。如果任何一个参数是绝对路径，那之前的参数就会被丢弃，然后连接继续（如果在Windows上，如果有盘符，盘符也会被丢弃）。返回的值是path1、path2等等的连接，每个非空部分除了最后一个后面只跟随一个目录分隔符（os.sep）。（这意味着最后一部分为空将导致路径以分隔符结尾。）注意，在windows上, 由于每个盘符都是一个目录，因此，os.path.join("c:", "foo") 将返回一个C盘的相对路径，即基于C盘C:的绝对路径 (c:\foo), 而非一个相对路径c:foo.
Normalize the case of a pathname.On Unix and Mac OS X, this returns the path unchanged;在大小写不敏感的系统上，将路径名转换成小写。On Windows, it also converts forward slashes to backward slashes.
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 normcase().
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.
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 os.curdir.
Availability: Windows, Unix.
New in version 2.6.
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.
Return True if the file descriptors fp1 and fp2 refer to the same file.
Availability: Unix.
Return True if the stat tuples stat1 and stat2 refer to the same file.These structures may have been returned by os.fstat(), os.lstat(), or os.stat().This function implements the underlying comparison used by samefile() and sameopenfile().
Availability: Unix.
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 dirname() and basename().
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.
New in version 1.3.
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.
将 path 分隔成一个(unc, rest)对，unc 是UNC挂载点（例如r'\\hostmount'），rest 是路径剩下的部分（例如 r'\path\file.ext'）。For paths containing drive letters, unc will always be the empty string.
Availability: Windows.
Calls the function visit with arguments (arg, dirname, names) for each directory in the directory tree rooted at path (including path itself, if it is a directory).参数 dirname 表示访问的目录，参数 names 列出该目录中的文件（从os.listdir(dirname) 得到）。The visit function may modify names to influence the set of directories visited below dirname, e.g. to avoid visiting certain parts of the tree.(The object referred to by names must be modified in place, using del or slice assignment.)
Note
指向目录的符合链接不会被当作子目录，因此 walk() 将不会访问它们。To visit linked directories you must identify them with os.path.islink(file) and os.path.isdir(file), and invoke walk() as necessary.
Note
该函数已经被弃用，并且，为了鼓励使用 os.walk()，该函数在 Python 3 中已经被移除。
True if arbitrary Unicode strings can be used as file names (within limitations imposed by the file system).
New in version 2.3.