Speedup `os.path.relpath()`

[nineteendo]

Feature or enhancement

Proposal:

Currently both implemenatations of relpath() are a bit inefficient. So they could use some optimisations:

1. We don't need to apply normpath() before abspath(), it already normalises it:

   -start_abs = abspath(normpath(start))
   -path_abs = abspath(normpath(path))
   +start_abs = abspath(start)
   +path_abs = abspath(path)

2. We don't need to filter the segments, we just need to check if *_rest is empty:

   -start_list = [x for x in start_rest.split(sep) if x]
   -path_list = [x for x in path_rest.split(sep) if x]
   +start_list = start_rest.split(sep) if start_rest else []
   +path_list = path_rest.split(sep) if path_rest else []

3. We can use str.join() instead of os.path.join():

   -return join(*rel_list)
   +return sep.join(rel_list)

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-117607: Speedup os.path.relpath() #117608