Substitution in Python

Rewriting text with re.sub, including callbacks.

import re

messy = "call  me   maybe,  ok?"
tidy = re.sub(r"\s+", " ", messy)

redacted = re.sub(r"\d{3}-\d{4}", "XXX-XXXX", "ring 555-1234 now")


def shout_word(match):
    return match.group(0).upper()


emphatic = re.sub(r"\bmaybe\b", shout_word, tidy)
swapped = re.sub(r"(\w+)@(\w+)", r"\2 at \1", "ada@lovelace")

How it works

1. sub(r'\s+', ' ', ...) collapses whitespace.
2. A function replacement transforms each match.
3. Backreferences like \2 at \1 reorder captures.

Keywords and builtins used here

• def
• return
• shout_word

The run, in numbers

Lines

14

Characters to type

314

Tokens

111

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 63 seconds.

Type this snippet

Step 3 of 5 in Regular expressions, step 3 of 41 in Domain tools.

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