python继承list类

class FrequencyList(list):def __init__(self, members):super().__init__(members)def frequency(self):counts = {}for item in self:counts.setdefault(item, 0)counts[item] += 1return countsfoo = FrequencyList(['a', 'b', 'a', 'c', 'b'])
print(len(foo))
print(foo.frequency())
print(foo.pop())
print(foo.frequency())