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368 lines
10 KiB
Python
368 lines
10 KiB
Python
"""Common operations on Posix pathnames.
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Instead of importing this module directly, import os and refer to
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this module as os.path. The "os.path" name is an alias for this
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module on Posix systems; on other systems (e.g. Mac, Windows),
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os.path provides the same operations in a manner specific to that
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platform, and is an alias to another module (e.g. macpath, ntpath).
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Some of this can actually be useful on non-Posix systems too, e.g.
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for manipulation of the pathname component of URLs.
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"""
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import os
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import stat
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# Normalize the case of a pathname. Trivial in Posix, string.lower on Mac.
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# On MS-DOS this may also turn slashes into backslashes; however, other
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# normalizations (such as optimizing '../' away) are not allowed
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# (another function should be defined to do that).
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def normcase(s):
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"""Normalize case of pathname. Has no effect under Posix"""
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return s
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# Return whether a path is absolute.
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# Trivial in Posix, harder on the Mac or MS-DOS.
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def isabs(s):
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"""Test whether a path is absolute"""
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return s[:1] == '/'
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# Join pathnames.
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# Ignore the previous parts if a part is absolute.
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# Insert a '/' unless the first part is empty or already ends in '/'.
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def join(a, *p):
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"""Join two or more pathname components, inserting '/' as needed"""
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path = a
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for b in p:
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if b[:1] == '/':
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path = b
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elif path == '' or path[-1:] == '/':
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path = path + b
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else:
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path = path + '/' + b
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return path
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# Split a path in head (everything up to the last '/') and tail (the
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# rest). If the path ends in '/', tail will be empty. If there is no
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# '/' in the path, head will be empty.
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# Trailing '/'es are stripped from head unless it is the root.
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def split(p):
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"""Split a pathname. Returns tuple "(head, tail)" where "tail" is
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everything after the final slash. Either part may be empty."""
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i = p.rfind('/') + 1
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head, tail = p[:i], p[i:]
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if head and head <> '/'*len(head):
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while head[-1] == '/':
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head = head[:-1]
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return head, tail
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# Split a path in root and extension.
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# The extension is everything starting at the last dot in the last
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# pathname component; the root is everything before that.
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# It is always true that root + ext == p.
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def splitext(p):
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"""Split the extension from a pathname. Extension is everything from the
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last dot to the end. Returns "(root, ext)", either part may be empty."""
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root, ext = '', ''
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for c in p:
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if c == '/':
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root, ext = root + ext + c, ''
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elif c == '.':
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if ext:
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root, ext = root + ext, c
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else:
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ext = c
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elif ext:
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ext = ext + c
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else:
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root = root + c
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return root, ext
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# Split a pathname into a drive specification and the rest of the
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# path. Useful on DOS/Windows/NT; on Unix, the drive is always empty.
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def splitdrive(p):
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"""Split a pathname into drive and path. On Posix, drive is always
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empty."""
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return '', p
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# Return the tail (basename) part of a path.
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def basename(p):
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"""Returns the final component of a pathname"""
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return split(p)[1]
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# Return the head (dirname) part of a path.
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def dirname(p):
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"""Returns the directory component of a pathname"""
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return split(p)[0]
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# Return the longest prefix of all list elements.
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def commonprefix(m):
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"Given a list of pathnames, returns the longest common leading component"
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if not m: return ''
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prefix = m[0]
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for item in m:
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for i in range(len(prefix)):
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if prefix[:i+1] <> item[:i+1]:
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prefix = prefix[:i]
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if i == 0: return ''
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break
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return prefix
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# Get size, mtime, atime of files.
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def getsize(filename):
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"""Return the size of a file, reported by os.stat()."""
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st = os.stat(filename)
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return st[stat.ST_SIZE]
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def getmtime(filename):
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"""Return the last modification time of a file, reported by os.stat()."""
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st = os.stat(filename)
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return st[stat.ST_MTIME]
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def getatime(filename):
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"""Return the last access time of a file, reported by os.stat()."""
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st = os.stat(filename)
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return st[stat.ST_ATIME]
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# Is a path a symbolic link?
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# This will always return false on systems where os.lstat doesn't exist.
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def islink(path):
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"""Test whether a path is a symbolic link"""
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try:
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st = os.lstat(path)
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except (os.error, AttributeError):
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return 0
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return stat.S_ISLNK(st[stat.ST_MODE])
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# Does a path exist?
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# This is false for dangling symbolic links.
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def exists(path):
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"""Test whether a path exists. Returns false for broken symbolic links"""
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try:
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st = os.stat(path)
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except os.error:
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return 0
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return 1
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# Is a path a directory?
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# This follows symbolic links, so both islink() and isdir() can be true
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# for the same path.
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def isdir(path):
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"""Test whether a path is a directory"""
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try:
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st = os.stat(path)
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except os.error:
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return 0
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return stat.S_ISDIR(st[stat.ST_MODE])
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# Is a path a regular file?
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# This follows symbolic links, so both islink() and isfile() can be true
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# for the same path.
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def isfile(path):
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"""Test whether a path is a regular file"""
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try:
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st = os.stat(path)
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except os.error:
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return 0
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return stat.S_ISREG(st[stat.ST_MODE])
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# Are two filenames really pointing to the same file?
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def samefile(f1, f2):
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"""Test whether two pathnames reference the same actual file"""
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s1 = os.stat(f1)
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s2 = os.stat(f2)
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return samestat(s1, s2)
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# Are two open files really referencing the same file?
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# (Not necessarily the same file descriptor!)
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def sameopenfile(fp1, fp2):
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"""Test whether two open file objects reference the same file"""
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s1 = os.fstat(fp1)
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s2 = os.fstat(fp2)
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return samestat(s1, s2)
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# Are two stat buffers (obtained from stat, fstat or lstat)
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# describing the same file?
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def samestat(s1, s2):
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"""Test whether two stat buffers reference the same file"""
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return s1[stat.ST_INO] == s2[stat.ST_INO] and \
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s1[stat.ST_DEV] == s2[stat.ST_DEV]
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# Is a path a mount point?
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# (Does this work for all UNIXes? Is it even guaranteed to work by Posix?)
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def ismount(path):
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"""Test whether a path is a mount point"""
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try:
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s1 = os.stat(path)
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s2 = os.stat(join(path, '..'))
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except os.error:
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return 0 # It doesn't exist -- so not a mount point :-)
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dev1 = s1[stat.ST_DEV]
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dev2 = s2[stat.ST_DEV]
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if dev1 != dev2:
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return 1 # path/.. on a different device as path
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ino1 = s1[stat.ST_INO]
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ino2 = s2[stat.ST_INO]
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if ino1 == ino2:
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return 1 # path/.. is the same i-node as path
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return 0
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# Directory tree walk.
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# For each directory under top (including top itself, but excluding
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# '.' and '..'), func(arg, dirname, filenames) is called, where
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# dirname is the name of the directory and filenames is the list
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# of files (and subdirectories etc.) in the directory.
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# The func may modify the filenames list, to implement a filter,
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# or to impose a different order of visiting.
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def walk(top, func, arg):
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"""walk(top,func,arg) calls func(arg, d, files) for each directory "d"
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in the tree rooted at "top" (including "top" itself). "files" is a list
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of all the files and subdirs in directory "d".
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"""
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try:
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names = os.listdir(top)
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except os.error:
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return
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func(arg, top, names)
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for name in names:
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name = join(top, name)
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st = os.lstat(name)
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if stat.S_ISDIR(st[stat.ST_MODE]):
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walk(name, func, arg)
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# Expand paths beginning with '~' or '~user'.
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# '~' means $HOME; '~user' means that user's home directory.
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# If the path doesn't begin with '~', or if the user or $HOME is unknown,
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# the path is returned unchanged (leaving error reporting to whatever
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# function is called with the expanded path as argument).
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# See also module 'glob' for expansion of *, ? and [...] in pathnames.
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# (A function should also be defined to do full *sh-style environment
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# variable expansion.)
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def expanduser(path):
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"""Expand ~ and ~user constructions. If user or $HOME is unknown,
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do nothing."""
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if path[:1] <> '~':
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return path
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i, n = 1, len(path)
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while i < n and path[i] <> '/':
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i = i + 1
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if i == 1:
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if not os.environ.has_key('HOME'):
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return path
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userhome = os.environ['HOME']
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else:
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import pwd
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try:
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pwent = pwd.getpwnam(path[1:i])
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except KeyError:
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return path
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userhome = pwent[5]
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if userhome[-1:] == '/': i = i + 1
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return userhome + path[i:]
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# Expand paths containing shell variable substitutions.
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# This expands the forms $variable and ${variable} only.
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# Non-existent variables are left unchanged.
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_varprog = None
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def expandvars(path):
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"""Expand shell variables of form $var and ${var}. Unknown variables
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are left unchanged."""
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global _varprog
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if '$' not in path:
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return path
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if not _varprog:
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import re
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_varprog = re.compile(r'\$(\w+|\{[^}]*\})')
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i = 0
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while 1:
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m = _varprog.search(path, i)
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if not m:
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break
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i, j = m.span(0)
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name = m.group(1)
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if name[:1] == '{' and name[-1:] == '}':
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name = name[1:-1]
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if os.environ.has_key(name):
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tail = path[j:]
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path = path[:i] + os.environ[name]
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i = len(path)
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path = path + tail
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else:
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i = j
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return path
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# Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B.
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# It should be understood that this may change the meaning of the path
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# if it contains symbolic links!
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def normpath(path):
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"""Normalize path, eliminating double slashes, etc."""
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if path == '':
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return '.'
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initial_slash = (path[0] == '/')
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comps = path.split('/')
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new_comps = []
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for comp in comps:
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if comp in ('', '.'):
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continue
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if (comp != '..' or (not initial_slash and not new_comps) or
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(new_comps and new_comps[-1] == '..')):
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new_comps.append(comp)
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elif new_comps:
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new_comps.pop()
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comps = new_comps
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path = '/'.join(comps)
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if initial_slash:
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path = '/' + path
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return path or '.'
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def abspath(path):
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"""Return an absolute path."""
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if not isabs(path):
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path = join(os.getcwd(), path)
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return normpath(path)
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