python regex: replacing <number>st, <number>nd, <number>th etc in a adress with a single sub

Question

I have many adresses like "East 19th Street" or "West 141st Street" and I would like to remove the "th" and the "st" in a single call to re.sub.

re.sub("(\d+)st|(\d+)nd|(\d+)rd|(\d+)th", "g<1>", "East 19th Street")

doesn't work because it is not always the first gorup which is caught

I could chain the subs but it is dirty. Help appreciated

Answer 1

Let's try this:

re.sub(r"(\d+)(st|nd|rd|th)\b", r"\1", str)

or better

re.sub(r"(?<=\d)(st|nd|rd|th)\b", '', str)

\b prevents things like 21strange from being replaced.

To replace only grammatically correct constructs, you can also try:

re.sub(r"(?<=1\d)th\b|(?<=1)st\b|(?<=2)nd\b|(?<=3)rd\b|(?<=[04-9])th\b", r'', str)

This replaces 23rd and 44th but leaves invalid things like 23st intact. Don't know if this is worth the trouble though.