数组

class Array(object):

    def __init__(self,size=32):
        self._size = size
        self._items = [None] * size
    
    def __getitem__(self,index):
        return self._items[index]

    def __setitem(self,index,value):
        self._items[index] = value
    
    def __len__(self):
        return self._size

    def clear(self,value=None):
        for _ in range(self._items):
            self._items[_] = value
    
    def iter(self):
        for _ in self._items:
            yield _