262 lines
10 KiB
TeX
262 lines
10 KiB
TeX
\section{\module{os.path} ---
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Common pathname manipulations}
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\declaremodule{standard}{os.path}
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\modulesynopsis{Common pathname manipulations.}
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This module implements some useful functions on pathnames.
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\index{path!operations}
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\warning{On Windows, many of these functions do not properly
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support UNC pathnames. \function{splitunc()} and \function{ismount()}
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do handle them correctly.}
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\begin{funcdesc}{abspath}{path}
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Return a normalized absolutized version of the pathname \var{path}.
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On most platforms, this is equivalent to
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\code{normpath(join(os.getcwd(), \var{path}))}.
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\versionadded{1.5.2}
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\end{funcdesc}
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\begin{funcdesc}{basename}{path}
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Return the base name of pathname \var{path}. This is the second half
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of the pair returned by \code{split(\var{path})}. Note that the
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result of this function is different from the
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\UNIX{} \program{basename} program; where \program{basename} for
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\code{'/foo/bar/'} returns \code{'bar'}, the \function{basename()}
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function returns an empty string (\code{''}).
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\end{funcdesc}
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\begin{funcdesc}{commonprefix}{list}
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Return the longest path prefix (taken character-by-character) that is a
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prefix of all paths in
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\var{list}. If \var{list} is empty, return the empty string
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(\code{''}). Note that this may return invalid paths because it works a
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character at a time.
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\end{funcdesc}
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\begin{funcdesc}{dirname}{path}
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Return the directory name of pathname \var{path}. This is the first
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half of the pair returned by \code{split(\var{path})}.
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\end{funcdesc}
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\begin{funcdesc}{exists}{path}
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Return \code{True} if \var{path} refers to an existing path.
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Returns \code{False} for broken symbolic links.
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\end{funcdesc}
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\begin{funcdesc}{lexists}{path}
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Return \code{True} if \var{path} refers to an existing path.
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Returns \code{True} for broken symbolic links.
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Equivalent to \function{exists()} on platforms lacking
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\function{os.lstat()}.
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\versionadded{2.4}
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\end{funcdesc}
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\begin{funcdesc}{expanduser}{path}
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Return the argument with an initial component of \samp{\~} or
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\samp{\~\var{user}} replaced by that \var{user}'s home directory. An
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initial \samp{\~{}} is replaced by the environment variable
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\envvar{HOME}; an initial \samp{\~\var{user}} is looked up in the
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password directory through the built-in module
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\refmodule{pwd}\refbimodindex{pwd}. If the expansion fails, or if the
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path does not begin with a tilde, the path is returned unchanged.
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\end{funcdesc}
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\begin{funcdesc}{expandvars}{path}
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Return the argument with environment variables expanded. Substrings
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of the form \samp{\$\var{name}} or \samp{\$\{\var{name}\}} are
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replaced by the value of environment variable \var{name}. Malformed
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variable names and references to non-existing variables are left
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unchanged.
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\end{funcdesc}
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\begin{funcdesc}{getatime}{path}
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Return the time of last access of \var{path}. The return
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value is a number giving the number of seconds since the epoch (see the
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\refmodule{time} module). Raise \exception{os.error} if the file does
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not exist or is inaccessible.
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\versionadded{1.5.2}
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\versionchanged[If \function{os.stat_float_times()} returns True, the result is a floating point number]{2.3}
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\end{funcdesc}
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\begin{funcdesc}{getmtime}{path}
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Return the time of last modification of \var{path}. The return
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value is a number giving the number of seconds since the epoch (see the
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\refmodule{time} module). Raise \exception{os.error} if the file does
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not exist or is inaccessible.
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\versionadded{1.5.2}
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\versionchanged[If \function{os.stat_float_times()} returns True, the result is a floating point number]{2.3}
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\end{funcdesc}
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\begin{funcdesc}{getctime}{path}
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Return the system's ctime which, on some systems (like \UNIX) is the
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time of the last change, and, on others (like Windows), is the
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creation time for \var{path}. The return
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value is a number giving the number of seconds since the epoch (see the
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\refmodule{time} module). Raise \exception{os.error} if the file does
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not exist or is inaccessible.
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\versionadded{2.3}
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\end{funcdesc}
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\begin{funcdesc}{getsize}{path}
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Return the size, in bytes, of \var{path}. Raise
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\exception{os.error} if the file does not exist or is inaccessible.
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\versionadded{1.5.2}
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\end{funcdesc}
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\begin{funcdesc}{isabs}{path}
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Return \code{True} if \var{path} is an absolute pathname (begins with a
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slash).
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\end{funcdesc}
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\begin{funcdesc}{isfile}{path}
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Return \code{True} if \var{path} is an existing regular file. This follows
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symbolic links, so both \function{islink()} and \function{isfile()}
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can be true for the same path.
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\end{funcdesc}
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\begin{funcdesc}{isdir}{path}
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Return \code{True} if \var{path} is an existing directory. This follows
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symbolic links, so both \function{islink()} and \function{isdir()} can
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be true for the same path.
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\end{funcdesc}
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\begin{funcdesc}{islink}{path}
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Return \code{True} if \var{path} refers to a directory entry that is a
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symbolic link. Always \code{False} if symbolic links are not supported.
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\end{funcdesc}
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\begin{funcdesc}{ismount}{path}
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Return \code{True} if pathname \var{path} is a \dfn{mount point}: a point in
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a file system where a different file system has been mounted. The
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function checks whether \var{path}'s parent, \file{\var{path}/..}, is
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on a different device than \var{path}, or whether \file{\var{path}/..}
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and \var{path} point to the same i-node on the same device --- this
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should detect mount points for all \UNIX{} and \POSIX{} variants.
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\end{funcdesc}
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\begin{funcdesc}{join}{path1\optional{, path2\optional{, ...}}}
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Joins one or more path components intelligently. If any component is
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an absolute path, all previous components are thrown away, and joining
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continues. The return value is the concatenation of \var{path1}, and
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optionally \var{path2}, etc., with exactly one directory separator
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(\code{os.sep}) inserted between components, unless \var{path2} is
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empty. Note that on Windows, since there is a current directory for
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each drive, \function{os.path.join("c:", "foo")} represents a path
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relative to the current directory on drive \file{C:} (\file{c:foo}), not
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\file{c:\textbackslash\textbackslash foo}.
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\end{funcdesc}
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\begin{funcdesc}{normcase}{path}
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Normalize the case of a pathname. On \UNIX, this returns the path
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unchanged; on case-insensitive filesystems, it converts the path to
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lowercase. On Windows, it also converts forward slashes to backward
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slashes.
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\end{funcdesc}
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\begin{funcdesc}{normpath}{path}
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Normalize a pathname. This collapses redundant separators and
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up-level references, e.g. \code{A//B}, \code{A/./B} and
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\code{A/foo/../B} all become \code{A/B}. It does not normalize the
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case (use \function{normcase()} for that). On Windows, it converts
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forward slashes to backward slashes. It should be understood that this may
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change the meaning of the path if it contains symbolic links!
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\end{funcdesc}
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\begin{funcdesc}{realpath}{path}
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Return the canonical path of the specified filename, eliminating any
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symbolic links encountered in the path.
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Availability: \UNIX.
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\versionadded{2.2}
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\end{funcdesc}
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\begin{funcdesc}{samefile}{path1, path2}
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Return \code{True} if both pathname arguments refer to the same file or
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directory (as indicated by device number and i-node number).
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Raise an exception if a \function{os.stat()} call on either pathname
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fails.
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Availability: Macintosh, \UNIX.
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\end{funcdesc}
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\begin{funcdesc}{sameopenfile}{fp1, fp2}
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Return \code{True} if the file objects \var{fp1} and \var{fp2} refer to the
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same file. The two file objects may represent different file
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descriptors.
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Availability: Macintosh, \UNIX.
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\end{funcdesc}
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\begin{funcdesc}{samestat}{stat1, stat2}
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Return \code{True} if the stat tuples \var{stat1} and \var{stat2} refer to
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the same file. These structures may have been returned by
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\function{fstat()}, \function{lstat()}, or \function{stat()}. This
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function implements the underlying comparison used by
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\function{samefile()} and \function{sameopenfile()}.
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Availability: Macintosh, \UNIX.
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\end{funcdesc}
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\begin{funcdesc}{split}{path}
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Split the pathname \var{path} into a pair, \code{(\var{head},
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\var{tail})} where \var{tail} is the last pathname component and
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\var{head} is everything leading up to that. The \var{tail} part will
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never contain a slash; if \var{path} ends in a slash, \var{tail} will
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be empty. If there is no slash in \var{path}, \var{head} will be
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empty. If \var{path} is empty, both \var{head} and \var{tail} are
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empty. Trailing slashes are stripped from \var{head} unless it is the
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root (one or more slashes only). In nearly all cases,
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\code{join(\var{head}, \var{tail})} equals \var{path} (the only
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exception being when there were multiple slashes separating \var{head}
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from \var{tail}).
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\end{funcdesc}
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\begin{funcdesc}{splitdrive}{path}
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Split the pathname \var{path} into a pair \code{(\var{drive},
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\var{tail})} where \var{drive} is either a drive specification or the
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empty string. On systems which do not use drive specifications,
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\var{drive} will always be the empty string. In all cases,
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\code{\var{drive} + \var{tail}} will be the same as \var{path}.
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\versionadded{1.3}
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\end{funcdesc}
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\begin{funcdesc}{splitext}{path}
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Split the pathname \var{path} into a pair \code{(\var{root}, \var{ext})}
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such that \code{\var{root} + \var{ext} == \var{path}},
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and \var{ext} is empty or begins with a period and contains
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at most one period.
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\end{funcdesc}
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\begin{funcdesc}{walk}{path, visit, arg}
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Calls the function \var{visit} with arguments
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\code{(\var{arg}, \var{dirname}, \var{names})} for each directory in the
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directory tree rooted at \var{path} (including \var{path} itself, if it
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is a directory). The argument \var{dirname} specifies the visited
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directory, the argument \var{names} lists the files in the directory
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(gotten from \code{os.listdir(\var{dirname})}).
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The \var{visit} function may modify \var{names} to
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influence the set of directories visited below \var{dirname}, e.g., to
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avoid visiting certain parts of the tree. (The object referred to by
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\var{names} must be modified in place, using \keyword{del} or slice
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assignment.)
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\begin{notice}
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Symbolic links to directories are not treated as subdirectories, and
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that \function{walk()} therefore will not visit them. To visit linked
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directories you must identify them with
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\code{os.path.islink(\var{file})} and
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\code{os.path.isdir(\var{file})}, and invoke \function{walk()} as
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necessary.
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\end{notice}
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\note{The newer \function{\refmodule{os}.walk()} generator supplies
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similar functionality and can be easier to use.}
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\end{funcdesc}
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\begin{datadesc}{supports_unicode_filenames}
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True if arbitrary Unicode strings can be used as file names (within
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limitations imposed by the file system), and if
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\function{os.listdir()} returns Unicode strings for a Unicode
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argument.
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\versionadded{2.3}
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\end{datadesc}
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