decoding & encoding url params (not query strings) in Python

Python doesn't seem to have a function to do this - or documentation that an existing function can do this - and I am a bit lost combing through RFCs.

I have a url that I have parsed with urlparse:

url = "https://example.com/path/to;jsessionid=foo?foo=bar&biz=bang"

It has both "params" and a "query string"

I need to decode/recode the params (jsessionid=foo)

For decoding, I tried urlparse.parse_qs and it works fine. Looking at the code, it appears to use ; as primary delimiter in a nested list comprehension:

def parse_qsl(qs
    ...
    pairs = [s2 for s1 in qs.split('&') for s2 in s1.split(';')]

In terms of rebuilding the params though, it seems that I'd need to re-implement urllib.urlencode and just change the delimiter from & to ;.

That seems a bit odd to me, and I feel like I must be missing something obvious.

edit: After thinking, I could probably just do params = params.replace("&", ";") as the key/value payloads shouldn't be affected since the RFC has both characters reserved.