`string`

Character class constants, a Formatter extension point for str.format, and Template for $identifier substitution.

Source-of-record: Lib/string.py, string docs.

Character classes

Constant	Value
`ascii_lowercase`	`'abcdefghijklmnopqrstuvwxyz'`.
`ascii_uppercase`	`'ABCDEFGHIJKLMNOPQRSTUVWXYZ'`.
`ascii_letters`	Concatenation of the two above.
`digits`	`'0123456789'`.
`hexdigits`	`'0123456789abcdefABCDEF'`.
`octdigits`	`'01234567'`.
`punctuation`	ASCII punctuation.
`whitespace`	Space, tab, newline, return, formfeed, vertical tab.
`printable`	Digits + letters + punctuation + whitespace.

Backbone of str.format / f-strings. Override to customise.

Method	Override role
`format(format_string, args, *kwargs)`	Top-level entry.
`vformat(format_string, args, kwargs)`	Bypass packing.
`parse(format_string)`	Iterator of `(literal, field_name, spec, conversion)`.
`get_field(field_name, args, kwargs)`	Resolve `0.attr[key]`.
`get_value(key, args, kwargs)`	Look up by name or position.
`check_unused_args(used_args, args, kwargs)`	Validation hook.
`format_field(value, format_spec)`	Apply format spec.
`convert_field(value, conversion)`	Apply `!s`, `!r`, `!a`.

Template performs $identifier and ${identifier} substitution without invoking str.format's richer mini-language.

Method	Effect
`Template(template)`	Construct.
`substitute(mapping={}, /, **kwargs)`	Replace; missing keys raise `KeyError`.
`safe_substitute(mapping={}, /, **kwargs)`	Leave missing placeholders intact.
`get_identifiers()`	Names referenced (3.11+).
`is_valid()`	Predicate (3.11+).

Customise via Template.delimiter, Template.idpattern, Template.braceidpattern, Template.flags.

string.capwords(s, sep=None) splits on whitespace and capitalises each word. Equivalent to sep.join(x.capitalize() for x in s.split(sep)).

Area	State
All character class constants	Complete.
`Formatter` API	Complete.
`Template` (incl. `is_valid`)	Complete.
`capwords`	Complete.