How to use regex with optional characters in python?

Question

Say I have a string

"3434.35353"

and another string

"3593"

How do I make a single regular expression that is able to match both without me having to set the pattern to something else if the other fails? I know d+ would match the 3593, but it would not do anything for the 3434.35353, but (d+.d+) would only match the one with the decimal and return no matches found for the 3593.

I expect m.group(1) to return:

"3434.35353"

or

"3593"

Answer 1

You can put a ? after a group of characters to make it optional.

You want a dot followed by any number of digits .d+, grouped together (.d+), optionally (.d+)?. Stick that in your pattern:

import re
print re.match("(d+(.d+)?)", "3434.35353").group(1)

3434.35353

print re.match("(d+(.d+)?)", "3434").group(1)

3434