二. python数组和列表

class Array(object):
    def __init__(self, size=32):
        self._size=size
        self._item=[None]*size
    def __getitem__(self, item):
        return self._item[item]
    def __setitem__(self, key, value):
        self._item[key]=value
    def __len__(self):
        return self._size
    def clear(self):
        for i in range(self._size):
            self._item[i]=None
    def __iter__(self):
        for i in self._item:
            yield i

def test_array():
    size=10
    a=Array(size)
    a[0]=1
    assert a[0]==1

    a.clear()
    assert a[0] is None