python regex re.compile and re.search

Question

import re

real_comp = re.compile(r'[0-9]*')
real_comp.search('+123i').group()
Out[7]: ''

I am expecting the the result as "123", but it returns empty. What's wrong?

You are searching for a substring of *zero or more* digits. Your string `+123i` does indeed contain such a substring, of zero length, at the very start. You probably want `+` (one or more) instead of `*` — jasonharper, Feb 20 '19 at 18:35

score 1 · Accepted Answer · answered Feb 20 '19 at 18:35

You'll need another quantifier, namely a +:

import re

real_comp = re.compile(r'([0-9]+)')
print(real_comp.search('+123i').group())

Which yields

Otherwise the regex engine reports a match before the very first consumed char ( [0-9]* is always true).

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