Are Python strings mutable?

No. Python str objects are immutable, so every method that appears to change a string actually returns a new string and leaves the original unchanged. For example s.upper() does not modify s; you must assign the result, like s = s.upper(). This is why methods such as replace and strip return a value rather than acting in place.

What is the difference between strip, lstrip, and rstrip?

strip removes leading and trailing characters, lstrip removes only leading ones, and rstrip removes only trailing ones. By default they remove whitespace, but you can pass a string of characters to remove any of those from the relevant end. The argument is a set of characters, not a prefix or suffix, so strip('ab') removes any a or b, not the literal 'ab'.

How do I remove a prefix or suffix instead of characters?

Use removeprefix and removesuffix, added in Python 3.9. Unlike strip, they remove the exact substring once if it is present and otherwise return the string unchanged. So 'test.py'.removesuffix('.py') gives 'test', whereas rstrip('.py') would strip any trailing p, y, or dot character and corrupt the result.

What is the difference between find and index?

Both locate the first occurrence of a substring and return its position. The difference is on failure: find returns -1 when the substring is absent, while index raises a ValueError. Use find when a missing substring is expected and you want to test the result; use index when absence is a genuine error you want to surface.

Is this the complete list of str methods?

It covers every standard str method in current Python 3 across case, search, split and join, trim and pad, testing, and encoding. A few rarely-used methods like maketrans are noted. For exact version availability and edge-case behavior, consult the official Python documentation's Text Sequence Type page.

Python String Methods Reference

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Python’s str type is immutable, so every method here returns a new string rather than changing the original. The methods cover case conversion, searching, splitting and joining, trimming, testing, and encoding. This is a searchable offline reference.

How it works

Each method lists its signature and return type. Because strings are immutable, a call like s.upper() produces a new string — you must assign it (s = s.upper()) to keep the result. The groups are:

Case — upper, lower, title, capitalize, casefold, swapcase.
Search — find, index, count, startswith, endswith. find returns -1 on failure; index raises ValueError.
Split / join — split, rsplit, splitlines, partition, join.
Trim / pad — strip, lstrip, rstrip, removeprefix, removesuffix, center, ljust, rjust, zfill.
Test — isalpha, isdigit, isalnum, isspace, isidentifier, etc.
Transform — replace, translate, format, format_map, encode.

Example

"  Hello, World  ".strip().lower().replace(",", "")
# -> 'hello world'

"file.tar.gz".removesuffix(".gz")  # -> 'file.tar'

Note strip('.py') would remove any trailing ., p, or y character — use removesuffix('.py') to drop the exact substring once.

Notes

strip/lstrip/rstrip take a set of characters, not a prefix — use removeprefix/removesuffix (Python 3.9+) for exact substrings.
str.join is called on the separator: ", ".join(items).
This reference covers the standard str methods. For exact version availability consult the official Python docs.