110 – Non-greedy regex quantifiers

The quantifiers *, +, and ?, in regular expressions, are all greedy. This means that they will try to match as much as possible, while still allowing the full pattern to match:

import re

html = "<a href='mathspp.com'>My site</a>"
#                            ^          ^
# Note how there are two '>' in the string.

greedy = re.compile(r"<a.*>")

print(re.match(greedy, html).group())
# <a href='mathspp.com'>My site</a>

However, sometimes you don’t want to match as much as possible; you want to match as little as possible. When that’s the case, you can add a question mark ? to the quantifiers, making them *?, +?, and ??. These are non-greedy and will try to match as few characters as possible:

non_greedy = re.compile(r"<a.*?>")

print(re.match(non_greedy, html).group())
# <a href='mathspp.com'>