String literals, str(value), and methods returning strings. All methods return copies; strings are immutable.
| Method | Meaning |
|---|
.length | Character count, same as len(s). Property: no parens |
.upper() / .lower() | All upper / lower |
.title() / .capitalize() / .swapcase() | Titlecase runs / first-char titlecase + rest lower / swap every character |
.casefold() | Unicode case folding for caseless comparison (stronger than lower() beyond ASCII) |
| Method | Meaning |
|---|
.strip(chars=None) / .lstrip / .rstrip | Trim whitespace, or a SET of characters (not a substring): "...hello...".strip(".") → "hello" |
.split(sep=None, maxsplit=-1) | sep=None: any whitespace separates, runs collapse; a literal non-empty separator preserves empty fields |
.splitlines(keepends=False) | Split on Python line boundaries (\n, \r\n, \r, vertical tab, form feed, NEL, line/paragraph separators) |
.join(iterable) | Concatenate strings with this string between: ",".join(["a","b"]) → "a,b" |
.partition(sep) / .rpartition(sep) | (before, sep, after) at the first / last occurrence; not-found returns (original, "", "") / ("", "", original) |
| Method | Meaning |
|---|
.find(sub, start=0, end=None) / .rfind | Lowest / highest index or -1 |
.index(sub, ...) / .rindex | Like find but raise when absent |
.count(sub, start=0, end=None) | Non-overlapping occurrences (empty sub returns length + 1) |
.replace(old, new, count=-1) | Replace occurrences, optionally limited |
.startswith(prefix, start=0, end=None) / .endswith(suffix, ...) | Accept a single string or a tuple of strings |
.removeprefix(prefix) / .removesuffix(suffix) | Strip only if present |
| Method | Meaning |
|---|
.zfill(width) | Leading zeros; preserves a leading sign |
.center(width, fill=" ") / .ljust / .rjust | Pad to width with a single fill character |
.format(*args, **kwargs) | {} auto-numbered, {0} positional, {name} keyword. For format specs ({x:>10}, {x!r}) prefer f-strings |
.isdigit() · .isalpha() · .isalnum() · .isspace() · .islower() · .isupper() · .istitle(): all require a non-empty string (case predicates require at least one cased character).
