You're on the trail of a regex that's gone rogue. Last seen near the 'import' statement, its last match was a '/^\\d+/'.
Regular Expressions Are Our Friends - A guide to capturing the truth.
Escape from Regex - A tale of backslashes and escapes.
But be careful, regex can be deadly, especially if you're not careful.
import re
s = "12345"
match = re.search(r"\\d+", s)
if match:
print(match.group())