深浅拷贝

深浅拷贝
浅拷贝，只会拷贝第一层b = a.copy()
深拷贝，相当于克隆一份import copy
b = copy.copy()#shallow copy
c = copy.deepcopy()#deep copy
a = [[1,2],3,4]
c=a
b = a.copy()#和赋值还是有区别的，赋值指向整体地址
b[1]=5#浅拷贝，只会拷贝第一层
print(a,'---',b,'---',c)#[[1, 2], 3, 4] --- [[1, 2], 5, 4]
b[0][1]=9#
print(a,'---',b,'---',c)#[[1, 9], 3, 4] --- [[1, 9], 3, 4]