How to use regex with optional characters in python?

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)

This regex should work:

d+(.d+)?

It matches one ore more digits (d+) optionally followed by a dot and one or more digits ((.d+)?).

Use the one or zero quantifier, ?. Your regex becomes: (d+(.d+)?).

See Chapter 8 of the TextWrangler manual for more details about the different quantifiers available, and how to use them.