import copy
a = [1,2,3,4]
b = []
c = []
d = []
b.append(a[:])
d.append(copy.deepcopy(a)) # 和[:] 等价
c.append(a)
a.pop()
print(b)
print(c)
print(d)
print(id(a[:])) # id不一样
print(id(a))