[python] os.path说明

os.path — Common pathname manipulations操作

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任意的 file names on Unix should use bytes objects to represent path names. Vice versa相反不足, 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.

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.)

See also：The pathlib module offers high-level path objects.

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. 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

os.path.abspath(path)

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

返回文件的绝对路径

Changed in version 3.6: Accepts a path-like object.

os.path.basename(path)

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 ('').

Changed in version 3.6: Accepts a path-like object.

os.path.commonpath(paths)

Return the longest common sub-path of each pathname in the sequence paths. Raise ValueError if paths contains both absolute and relative pathnames, or if paths is empty. Unlike commonprefix(), this returns a valid path.

Availability: Unix, Windows

New in version 3.5.

Changed in version 3.6: Accepts a sequence of path-like objects.

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

 

This function may return invalid paths because it works a character at a time. To obtain a valid path, see commonpath().

>>>

>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
'/usr/l'

>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
'/usr'

Changed in version 3.6: Accepts a path-like object.

os.path.dirname(path)

Return the directory name of pathname path. This is the first element of the pair returned by passing path to the function split().

Changed in version 3.6: Accepts a path-like object.

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

Changed in version 3.3: path can now be an integer: True is returned if it is an open file descriptor, False otherwise.

Changed in version 3.6: Accepts a path-like object.

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().

Changed in version 3.6: Accepts a path-like object.

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.

Changed in version 3.6: Accepts a path-like object.

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}.

Changed in version 3.6: Accepts a path-like object.

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). RaiseOSError 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). RaiseOSError if the file does not exist or is inaccessible.

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

Changed in version 3.6: Accepts a path-like object.

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 for path. The return value is a number giving the number of seconds since the epoch (see the time module). Raise OSError if the file does not exist or is inaccessible.

Changed in version 3.6: Accepts a path-like object.

os.path.getsize(path)

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

Changed in version 3.6: Accepts a path-like object.

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.

Changed in version 3.6: Accepts a path-like object.

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.

Changed in version 3.6: Accepts a path-like object.

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.

Changed in version 3.6: Accepts a path-like object.

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.

Changed in version 3.6: Accepts a path-like object.

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. On POSIX, 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. On Windows, a drive letter root and a share UNC are always mount points, and for any other path GetVolumePathName is called to see if it is different from the input path.

New in version 3.4: Support for detecting non-root mount points on Windows.

Changed in version 3.6: Accepts a path-like object.

os.path.join(path, *paths)

Join one or more path components intelligently. The return value is the concatenation of path 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), not c:\foo.

Changed in version 3.6: Accepts a path-like object for path and paths.

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. Raise a TypeError if the type of path is not str or bytes (directly or indirectly through the os.PathLike interface).

Changed in version 3.6: Accepts a path-like object.

os.path.normpath(path)

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().

Changed in version 3.6: Accepts a path-like object.

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).

Changed in version 3.6: Accepts a path-like object.

os.path.relpath(path, start=os.curdir)

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: Unix, Windows.

Changed in version 3.6: Accepts a path-like object.

os.path.samefile(path1, path2)

Return True if both pathname arguments refer to the same file or directory. This is determined by the device number and i-node number and raises an exception if an os.stat() call on either pathname fails.

Availability: Unix, Windows.

Changed in version 3.2: Added Windows support.

Changed in version 3.4: Windows now uses the same implementation as all other platforms.

Changed in version 3.6: Accepts a path-like object.

os.path.sameopenfile(fp1, fp2)

Return True if the file descriptors fp1 and fp2 refer to the same file.

Availability: Unix, Windows.

Changed in version 3.2: Added Windows support.

Changed in version 3.6: Accepts a path-like object.

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 os.fstat(), os.lstat(), or os.stat(). This function implements the underlying comparison used by samefile() and sameopenfile().

Availability: Unix, Windows.

Changed in version 3.4: Added Windows support.

Changed in version 3.6: Accepts a path-like object.

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 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().

Changed in version 3.6: Accepts a path-like object.

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")

Changed in version 3.6: Accepts a path-like object.

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 3.6: Accepts a path-like object.

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).