r"""
The examples below are Py2/3 compatible

>>> assert next(filter(None, [0,1,0,0,1]).__iter__()) == 1
>>> next(filter(None, [0,0,0,0,0]).__iter__())
Traceback (most recent call last):
    ...
StopIteration
>>> next(filter(None, [         ]).__iter__())
Traceback (most recent call last):
    ...
StopIteration


>>> def func(L, default=None):
...     for i in filter(None, L):
...         return i
...     return default
>>> assert func([0,1,0,0,1]) == 1
>>> assert func([0,0,0,0,0]) == None
>>> assert func([         ]) == None


>>> assert (list(filter(None, [0,1,0,0,1])) or [None])[0] == 1
>>> assert (list(filter(None, [0,0,0,0,0])) or [None])[0] == None
>>> assert (list(filter(None, [         ])) or [None])[0] == None
"""