python：item系列(__getitem__ __setitem__ __delitem__)

class B:
    def __str__(self):
        return ‘123456‘
    def __getitem__(self, item):
        print(self, item)
        return getattr(self, item)
    def __setitem__(self, key, value):
        print(self, key, value)
        setattr(self, key, value)
    def __delitem__(self, key):
        print(self, key)
        delattr(self, key)
b = B()
b[‘k‘] = ‘v1‘
print(b[‘k‘])
# del b[‘k‘]
print(b[‘k‘])
print(b)

class B:
    def __init__(self, lst):
        self.lst = lst
    def __getitem__(self, item):
        return self.lst[item]
    def __setitem__(self, key, value):
        self.lst[key] = value
    def __delitem__(self, key):
        self.lst.pop(key)
b = B([‘111‘,‘222‘,‘333‘,‘444‘,‘555‘])
print(b.lst[0])
print(b[0])
b[0] = ‘1111‘
print(b.lst)
del b[1]
print(b.lst)