Python/Regex: Get all strings between any two characters

Question

I have a use case that requires the identification of many different pieces of text between any two characters.

For example,

1. String between a single space and (: def test() would return test
2. String between a word and space (paste), and a special character (/): @paste "game_01/01" would return "game_01
3. String between a single space and ( with multiple target strings: } def test2() { Hello(x, 1) would return test2 and Hello

To do this, I'm attempting to write something generic that will identify the shortest string between any two characters.

My current approach is (from chrisz):

pattern = '{0}(.*?){1}'.format(re.escape(separator_1), re.escape(separator_2))

And for the first use case, separator_1 = \s and separator_2 = (. This isn't working so evidently I am missing something but am not sure what.

tl;dr How can I write a generic regex to parse the shortest string between any two characters?

• Note: I know there are many examples of this but they seem quite specific and I'm looking for a general solution if possible.

Answer 1

Let me know if this is what you are looking for:

import re

def smallest_between_two(a, b, text):
    return min(re.findall(re.escape(a)+"(.*?)"+re.escape(b),text), key=len)

print(smallest_between_two(' ', '(', 'def test()'))
print(smallest_between_two('[', ']', '[this one][not this one]'))
print(smallest_between_two('paste ', '/', '@paste "game_01/01"'))

Output:

test
this one
"game_01

To add an explanation to what this does:

re.findall():

Return all non-overlapping matches of pattern in string, as a list of strings

re.escape()

Escape all the characters in pattern except ASCII letters and numbers. This is useful if you want to match an arbitrary literal string that may have regular expression metacharacters in it

(.*?)

.*? matches any character (except for line terminators)

*? Quantifier — Matches between zero and unlimited times, as few times as possible, expanding as needed (lazy)

So our regular expression matches any character (not including line terminators) between two arbitrary escaped strings, and then returns the shortest length string from the list that re.findall() returns.