def is_number(a):
if isinstance(a, (int, float, long, complex,
sage.rings.all.CommutativeRingElement)):
return True
elif hasattr(a, 'parent'):
numgen = sage.rings.number_field.number_field.NumberField_generic
parent = a.parent()
return CC.has_coerce_map_from(parent) or \
isinstance(parent, numgen) or \
(hasattr(parent, "is_field") and hasattr(parent, "is_finite")
and parent.is_field() and parent.is_finite())
else:
return False
