Matching optional numbers in regex

Question

This one is probably a simple one, but I could not find an example that's simple enough to understand (sorry, I'm new with RegEx).

I'm writing some Python code to search for any string that matches any of the following examples:

float[20]
float[7532]
float[]

So this is what I have so far:

import re
p = re.compile('float\[[0-9]+\]')
print p.match("float[20]")
print p.match("float[7532]")
print p.match("float[]")

The code works great for the first and second scenarios, but not the third (no numbers between brackets). What's the best way to add that condition?

Thanks a lot!

Answer 1

p = re.compile('float\[[0-9]*\]')

putting a * after the character class means 0 or matches of the character class.

Answer 2

Try

float\[\d*\]

\d is a shortcut for [0-9]. The asterisk matches 0..n (any number) of characters of the character class.