The :func:`locale.localeconv` function now sets temporarily the LC_CTYPE locale to the LC_NUMERIC locale to decode decimal_point and thousands_sep byte strings if they are non-ASCII or longer than 1 byte, and the LC_NUMERIC locale is different than the LC_CTYPE locale. This temporary change affects other threads.

Same change for the :meth:`str.format` method when formatting a number (:class:`int`, :class:`float`, :class:`complex`, :class:`decimal.Decimal` and subclasses) with the n type (ex: '{:n}'.format(1234)).