nessita

def one(iterable):
    """Return the object in the given iterable that evaluates to True.

    If the given iterable has more than one object that evaluates to True,
    or if there is no object that fulfills such condition, return None.

    >>> one((True, False, False))
    True
    >>> one((True, False, True))
    >>> one((0, 0, 'a'))