Check if string in the exact form of “,” in Python

Question

I\'m converting a string of two integers into a tuple. I need to make sure my string is formatted exactly in the form of \",\" with the comm

Answer 1

Sounds like a job for regular expressions.

import re
re.match("^\d+,\d+$", some_string)

• ^ matches start of string
• \d+ matches one or more digits
• , matches comma literal
• $ matches end of string

Some testcases:

assert re.match("^\d+,\d+$", "123,123")
assert not re.match("^\d+,\d+$", "123,123 ")  # trailing whitespace
assert not re.match("^\d+,\d+$", " 123,123")  # leading whitespace 
assert not re.match("^\d+,\d+$", "a,b")  # not digits
assert not re.match("^\d+,\d+$", "-1,3")  # minus sign is invalid

Return value of re.match is either MatchObject or None, fortunately they behave as expected in boolean context - MatchObject is truthy and None is falsy, as can be seen is assert statements above.