Patch 1339796: add a relpath() function to os.path.
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index 60c1fd0..99d7a4a 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -16,7 +16,7 @@
"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 @@
# 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)