New in version 1.1.1.
Return True when all elements in iterable l are numeric, otherwise False.
abjad> listtools.is_numeric([1, 2, 4.5, 5.5, Rational(13, 8)])
True
Defined equal to all([isinstance(x, (int, long, float, Rational)) for x in l]).
Note
implementation will probably change under Python 2.6.