strip in Python: Trim End Characters without Removing a Prefix

Start with a small, explicit task

Normalize a fictional imported label with spaces and marker characters. Then compare strip("AB-") with removeprefix("AB-") on a code whose legitimate body also contains A and B at its edges. The task is to preserve the body rather than deleting every matching end character.

Run the complete example

This original example was checked with Python 3.12.14. Save it as python_strip.py and run it with Python 3.12. It uses only the standard library. The assertions check the stated results.

raw = "  ##Shelf 4##  "
cleaned = raw.strip().strip("#")
code = "AB-BAZA"
stripped = code.strip("AB-")
prefix_removed = code.removeprefix("AB-")
assert cleaned == "Shelf 4"
assert raw == "  ##Shelf 4##  "
assert stripped == "Z"
assert prefix_removed == "BAZA"
assert "left-middle-right".strip("-") == "left-middle-right"
print(cleaned)
print(stripped)
print(prefix_removed)

Explain the result

The first trim removes outer whitespace; the second removes hash characters now exposed at the ends. The original raw string is unchanged, so the returned value must be retained. strip does not search through the middle of a string to remove every occurrence of a character.

The code example exposes the token mistake. strip("AB-") can remove A, B and hyphen in any sequence from either edge, leaving only Z. removeprefix removes the single matching AB- token and leaves BAZA intact. These are both valid operations, but only one satisfies the stated prefix-normalization rule.

Avoid these mistakes

Do not chain broad trimming rules without deciding which meaningful characters they may delete. If only the right end should be cleaned, choose rstrip with an explicit rule; if a known suffix should disappear, use removesuffix. removeprefix is available in Python 3.9 and later, including the checked 3.12 runtime.