def prod(iterable, ignore=False):
    """Takes the product sum of iterable. If ignore=True all elements except those that are None are multiplied. 
	If ignore=False, None is returned if any element is None. """
    x = None
    for i in iterable:
        if not i is None:
            if x is None:
                x = i
            else:
                x = x * i
        elif not ignore:
            return None
    return x
