How to join components of a path when you are constructing a URL in Python

Question

For example, I want to join a prefix path to resource paths like /js/foo.js.

I want the resulting path to be relative to the root of the server. In the above example if the prefix was "media" I would want the result to be /media/js/foo.js.

os.path.join does this really well, but how it joins paths is OS dependent. In this case I know I am targeting the web, not the local file system.

Is there a best alternative when you are working with paths you know will be used in URLs? Will os.path.join work well enough? Should I just roll my own?

Answer 1

>>> import urlparse
>>> urlparse.urljoin('/media/', 'js/foo.js')
'/media/js/foo.js'

Note that you will get different results from /js/foo.js and js/foo.js because the former begins with a slash which signifies that it already begins at the website root.

Answer 2

The basejoin function in the urllib package might be what you're looking for.

basejoin = urljoin(base, url, allow_fragments=True)
    Join a base URL and a possibly relative URL to form an absolute
    interpretation of the latter.

Edit: I didn't notice before, but urllib.basejoin seems to map directly to urlparse.urljoin, making the latter preferred.

Answer 3

Since, from the comments the OP posted, it seems he doesn't want to preserve "absolute URLs" in the join (which is one of the key jobs of urlparse.urljoin;-), I'd recommend avoiding that. os.path.join would also be bad, for exactly the same reason.

So, I'd use something like '/'.join(s.strip('/') for s in pieces) (if the leading / must also be ignored -- if the leading piece must be special-cased, that's also feasible of course;-).