Python 3.15 discourages re.match(), adds re.prefixmatch()

Python 3.15 marks re.match() as discouraged for new code, its release manager Hugo van Kemenade says. The function anchors at the start of a string but not the end, a gap that's confused developers for about 25 years. Anyone who reads re.match('foo', 'foobar') and expects a full-string check gets burned when trailing characters slide through unchecked, per Simon Willison's writeup.

3.15 doesn't change what any of the four functions do. re.search() matches anywhere in the string. re.fullmatch() matches the whole string. The new re.prefixmatch() does exactly what re.match() already does, just under a name that says so.

Anyone starting new code should default to re.fullmatch() or re.search() and treat re.match() as a legacy call, even though it isn't going anywhere.

Python's fix renamed the confusing function and left the original in place, rather than changing what it does. Existing re.match() calls keep running with no forced migration, so the old name doesn't disappear either. It just sits next to a clearer one.