Python string methods — a quick reference

Cleaning

• .strip() / .lstrip() / .rstrip() — remove surrounding whitespace.
• .replace(old, new) — swap substrings.

Casing

• .lower(), .upper(), .title(), .capitalize().
• .casefold() — aggressive lowercasing for comparisons.

Searching and testing

• .startswith() / .endswith() — boolean checks.
• .find() vs .index() — find returns -1, index raises.
• .count(sub) — how many times it appears.

Splitting and joining

",".join(["a", "b", "c"])   # 'a,b,c'
"a,b,c".split(",")          # ['a', 'b', 'c']

Strings are immutable, so every method returns a new string rather than changing the original.