"os.path" --- 常見的路徑名操作
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**原始碼：** Lib/posixpath.py (用於 POSIX 系統) 和 Lib/ntpath.py (用於
Windows).

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該模組實現了一些有用的路徑名操作函式。若要讀取或寫入檔案，請參閱
"open()" 函數，要存取檔案系統，請參閱 "os" 模組。路徑參數可以以字串、
位元組或任何依照 "os.PathLike" 協議實作的物件傳遞。

與 Unix shell 不同，Python 不會*自動*進行路徑展開（path expansions）。
當應用程式需要進行類似 shell 的路徑展開時，可以明確地呼叫
"expanduser()" 和 "expandvars()" 等函式。（另請參閱 "glob" 模組。）

也參考: "pathlib" 模組提供了高階的路徑物件。

備註:

  所有這些函數都只接受位元組或字串物件作為參數。如果回傳的是路徑或檔案
  名稱，結果將是相同型別的物件。

備註:

  由於不同的作業系統具有不同的路徑命名慣例，在標準函式庫中的路徑模組有
  數個版本可供使用，而 "os.path" 模組都會是運行 Python 之作業系統所適
  用本地路徑。然而，如果你想要操作*始終*以某個不同於本機格式表示的路徑
  ，你也可以引入並使用對應的模組。它們都具有相同的介面：

  * "posixpath" 用於 UNIX 形式的路徑

  * "ntpath" 用於 Windows 的路徑

在 3.8 版的變更: 對於包含有作業系統層級無法表示之字元或位元組的路徑，
"exists()"、"lexists()"、"isdir()"、"isfile()"、"islink()" 和
"ismount()" 函式現在會回傳 "False"，而不是引發例外。

os.path.abspath(path)

   回傳經正規化的絕對路徑名 *path* 。在大多數平台上，這等效於按照以下
   方式呼叫 "normpath()" 函式："normpath(join(os.getcwd(), path))"。

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.basename(path)

   回傳路徑名 *path* 的基底名稱。這是將 *path* 傳遞給函式 "split()" 後
   回傳結果中的第二個元素。請注意，此函式的結果與 Unix 的 **basename**
   程式不同；對於 "'/foo/bar/'"，**basename** 回傳 "'bar'"，而
   "basename()" 函式回傳空字串（"''"）。

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.commonpath(paths)

   回傳序列 *paths* 中每個路徑名的最長共同子路徑。如果 *paths* 同時包
   含絕對路徑和相對路徑、*paths* 位於不同的磁碟機或 *paths* 為空，則引
   發 "ValueError"。與 "commonprefix()" 不同，此函式回傳的是有效路徑。

   適用：Unix、Windows。

   在 3.5 版新加入.

   在 3.6 版的變更: 接受一個*類路徑物件*的序列。

os.path.commonprefix(list)

   回傳 *list* 中所有路徑的最長路徑前綴（逐字元比較）。如果 *list* 為
   空，則回傳空字串（"''"）。

   備註:

     由於此函式是逐字元比較，因此可能會回傳無效的路徑。若要獲得有效的
     路徑，請參考 "commonpath()" 函式。

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

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

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.dirname(path)

   回傳路徑名 *path* 的目錄名稱。這是將 *path* 傳遞給函式 "split()" 後
   回傳之成對結果中的第一個元素。

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.exists(path)

   如果 *path* 是一個存在的路徑或一個開啟的檔案描述器則回傳 "True"。對
   於已損壞的符號連結則回傳 "False"。在某些平台上，即使 *path* 實際存
   在，如果未被授予執行 "os.stat()" 的權限，此函式仍可能回傳 "False"。

   在 3.3 版的變更: 現在 *path* 可以是一個整數：如果它是一個開啟的檔案
   描述器，則回傳 "True"；否則回傳 "False"。

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.lexists(path)

   如果 *path* 是一個存在的路徑則回傳 "True"。對於已損壞的符號連結也回
   傳 "True"。在缺乏 "os.lstat()" 的平台上，與 "exists()" 函式等效。

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.expanduser(path)

   在 Unix 和 Windows 上，將引數中以 "~" 或 "~user" 開頭的部分替換為該
   *user* 的家目錄。

   在 Unix 上，如果環境變數 "HOME" 有被設置，則將初始的 "~" 替換為該變
   數的值；否則將使用內建模組 "pwd" 在密碼目錄中查找當前使用者的家目錄
   。對於初始的 "~user"，直接在密碼目錄中查找該使用者的家目錄。

   在 Windows 上，如果 "USERPROFILE" 有被設置，則使用該變數的值；否則
   將結合 "HOMEPATH" 和 "HOMEDRIVE"。對於初始的 "~user"，會檢查當前使
   用者的家目錄的最後一個目錄元件是否與 "USERNAME" 相符，如果相符則替
   換它。

   如果展開失敗或路徑不以波浪符號（tilde）開頭，則回傳原始路徑，不做任
   何變更。

   在 3.6 版的變更: 接受一個 *path-like object*。

   在 3.8 版的變更: 在 Windows 上不再使用 "HOME" 變數。

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}".

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.getatime(path)

   Return the time of last access of *path*.  The return value is a
   floating point number giving the number of seconds since the epoch
   (see the  "time" module).  Raise "OSError" if the file does not
   exist or is inaccessible.

os.path.getmtime(path)

   Return the time of last modification of *path*.  The return value
   is a floating point number giving the number of seconds since the
   epoch (see the  "time" module). Raise "OSError" if the file does
   not exist or is inaccessible.

   在 3.6 版的變更: 接受一個 *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.

   在 3.6 版的變更: 接受一個 *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.

   在 3.6 版的變更: 接受一個 *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.

   在 3.6 版的變更: 接受一個 *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.

   在 3.6 版的變更: 接受一個 *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.

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.islink(path)

   Return "True" if *path* refers to an "existing" directory entry
   that is a symbolic link.  Always "False" if symbolic links are not
   supported by the Python runtime.

   在 3.6 版的變更: 接受一個 *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.  It is not
   able to reliably detect bind mounts on the same filesystem.  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.

   在 3.4 版新加入: Support for detecting non-root mount points on
   Windows.

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.join(path, *paths)

   Join one or more path segments intelligently.  The return value is
   the concatenation of *path* and all members of **paths*, with
   exactly one directory separator following each non-empty part,
   except the last. That is, the result will only end in a separator
   if the last part is either empty or ends in a separator. If a
   segment is an absolute path (which on Windows requires both a drive
   and a root), then all previous segments are ignored and joining
   continues from the absolute path segment.

   On Windows, the drive is not reset when a rooted path segment
   (e.g., "r'\foo'") is encountered. If a segment is on a different
   drive or is an absolute path, all previous segments are ignored and
   the drive 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".

   在 3.6 版的變更: Accepts a *path-like object* for *path* and
   *paths*.

os.path.normcase(path)

   Normalize the case of a pathname.  On Windows, convert all
   characters in the pathname to lowercase, and also convert forward
   slashes to backward slashes. On other operating systems, return the
   path unchanged.

   在 3.6 版的變更: 接受一個 *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()".

   備註:

        On POSIX systems, in accordance with IEEE Std 1003.1 2013
        Edition; 4.13 Pathname Resolution, if a pathname begins with
        exactly two slashes, the first component following the leading
        characters may be interpreted in an implementation-defined
        manner, although more than two leading characters shall be
        treated as a single character.

     在 3.6 版的變更: 接受一個 *path-like object*。

os.path.realpath(path, *, strict=False)

   Return the canonical path of the specified filename, eliminating
   any symbolic links encountered in the path (if they are supported
   by the operating system).

   If a path doesn't exist or a symlink loop is encountered, and
   *strict* is "True", "OSError" is raised. If *strict* is "False",
   the path is resolved as far as possible and any remainder is
   appended without checking whether it exists.

   備註:

     This function emulates the operating system's procedure for
     making a path canonical, which differs slightly between Windows
     and UNIX with respect to how links and subsequent path components
     interact.Operating system APIs make paths canonical as needed, so
     it's not normally necessary to call this function.

   在 3.6 版的變更: 接受一個 *path-like object*。

   在 3.8 版的變更: Symbolic links and junctions are now resolved on
   Windows.

   在 3.10 版的變更: 新增 *strict* 參數。

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*.  On Windows, "ValueError"
   is raised when *path* and *start* are on different drives.

   *start* defaults to "os.curdir".

   適用：Unix、Windows。

   在 3.6 版的變更: 接受一個 *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.

   適用：Unix、Windows。

   在 3.2 版的變更: 新增對 Windows 的支援。

   在 3.4 版的變更: Windows now uses the same implementation as all
   other platforms.

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.sameopenfile(fp1, fp2)

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

   適用：Unix、Windows。

   在 3.2 版的變更: 新增對 Windows 的支援。

   在 3.6 版的變更: 接受一個 *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()".

   適用：Unix、Windows。

   在 3.4 版的變更: 新增對 Windows 的支援。

   在 3.6 版的變更: 接受一個 *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()".

   在 3.6 版的變更: 接受一個 *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:

      >>> splitdrive("c:/dir")
      ("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:

      >>> splitdrive("//host/computer/dir")
      ("//host/computer", "/dir")

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.splitext(path)

   Split the pathname *path* into a pair "(root, ext)"  such that
   "root + ext == path", and the extension, *ext*, is empty or begins
   with a period and contains at most one period.

   If the path contains no extension, *ext* will be "''":

      >>> splitext('bar')
      ('bar', '')

   If the path contains an extension, then *ext* will be set to this
   extension, including the leading period. Note that previous periods
   will be ignored:

      >>> splitext('foo.bar.exe')
      ('foo.bar', '.exe')
      >>> splitext('/foo/bar.exe')
      ('/foo/bar', '.exe')

   Leading periods of the last component of the path are considered to
   be part of the root:

      >>> splitext('.cshrc')
      ('.cshrc', '')
      >>> splitext('/foo/....jpg')
      ('/foo/....jpg', '')

   在 3.6 版的變更: 接受一個 *path-like object*。

os.path.supports_unicode_filenames

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