Regular expressions (regex) are a tool for finding patterns in strings. The standard library's re module defines functions for using regex patterns.
Example We can use regex to pull out all the numbers in a sentence:
>>> import re
>>> text = "On Oct 18 1963 a cat was launched aboard rocket #47"
>>> regex_pattern = r"[0-9]{1,3}" # Matches 1-3 digits
>>> re.findall(regex_pattern, text)
['18', '196', '3', '47'] # Notice the year is cut off