50 – Dynamic regex replacements

50 – Dynamic regex replacements#

The module re allows you to do dynamic string replacements. That is, search and replace for certain patterns and then replace them with other things that are not constant.

For this, you need a function that accepts a regex match and returns a replacement.

For example, the function replace below (admittedly, a poorly-named function), accepts a match and returns a string of asterisks that is as long as the full match:

def replace(match):
    return "*" * len(match.group(0))

Then, when using re.sub, pass it the function that does the replacements instead of specifying a fixed string:

import re

text = "I know Python, C, C++, JavaScript, and Haskell."

bad_words = r"C(\+\+)?|JavaScript"

print(re.sub(bad_words, replace, text))
# I know Python, *, ***, **********, and Haskell.