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Patch 1339796: add a relpath() function to os.path.

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This commit is contained in:
Collin Winter 2007-03-16 22:16:08 +00:00
parent 6de691d78c
commit 6f187743ff
7 changed files with 77 additions and 3 deletions
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28
Lib/ntpath.py
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@ -16,7 +16,7 @@ __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
"getatime","getctime", "islink","exists","lexists","isdir","isfile",
"ismount","walk","expanduser","expandvars","normpath","abspath",
"splitunc","curdir","pardir","sep","pathsep","defpath","altsep",
"extsep","devnull","realpath","supports_unicode_filenames"]
"extsep","devnull","realpath","supports_unicode_filenames","relpath"]
# strings representing various path-related bits and pieces
curdir = '.'
@ -465,3 +465,29 @@ realpath = abspath
# Win9x family and earlier have no Unicode filename support.
supports_unicode_filenames = (hasattr(sys, "getwindowsversion") and
sys.getwindowsversion()[3] >= 2)
def relpath(path, start=curdir):
"""Return a relative version of a path"""
if not path:
raise ValueError("no path specified")
start_list = abspath(start).split(sep)
path_list = abspath(path).split(sep)
if start_list[0].lower() != path_list[0].lower():
unc_path, rest = splitunc(path)
unc_start, rest = splitunc(start)
if bool(unc_path) ^ bool(unc_start):
raise ValueError("Cannot mix UNC and non-UNC paths (%s and %s)"
% (path, start))
else:
raise ValueError("path is on drive %s, start on drive %s"
% (path_list[0], start_list[0]))
# Work out how much of the filepath is shared by start and path.
for i in range(min(len(start_list), len(path_list))):
if start_list[i].lower() != path_list[i].lower():
break
else:
i += 1
rel_list = [pardir] * (len(start_list)-i) + path_list[i:]
return join(*rel_list)