os.path.join("/a","/b")

[Matthew Dixon Cowles]

I was a little surprised today to notice that

os.path.join("/a","/b") returns '/b'

(os.path is posixpath in this case of course) while

os.path.join("/a/","b") returns "/a/b"

which I expected from both. Poking back into my dusty archives, I find
that it has been that way since at least 1.4 so I presume that it's a
feature but I'll be darned if I can figure out the logic. It sure
doesn't seem to have much to do with joining. The module's docstring
just says "Join two or more pathname components, inserting '/' as
needed".

If someone could explain the logic to me, I'd be grateful.

Regards,
Matt