Python中a和a[:]有什么区别?

[]是引用 传址调用[:] 是复制 传值调用

发现用b=a[:], 再给b赋值, 不会影响a; 直接给a[:]赋值却会影响a

a=5b=aprint(a,b)b=3print(a,b)a=6print(a,b)5 55 36 3c=[1,2,3,4]d=cprint(c,d)c[0]=5print(c,d)d[0]=6print(c,d)[1, 2, 3, 4] [1, 2, 3, 4][5, 2, 3, 4] [5, 2, 3, 4][6, 2, 3, 4] [6, 2, 3, 4]c=[1,2,3,4]d=c[:]print(c,d)c[0]=5print(c,d)d[0]=6print(c,d)[1, 2, 3, 4] [1, 2, 3, 4][5, 2, 3, 4] [1, 2, 3, 4][5, 2, 3, 4] [6, 2, 3, 4]c=[1,2,[1,2,3],3,4]d=c[:] # 没有限制条件的分片表达式（L[:]）能够复制序列，但此法只能浅层复制; 在有嵌套情况跟着一起变化print(c,d)c[0]=5c[2][0]=7print(c,d)d[0]=6print(c,d)[1, 2, [1, 2, 3], 3, 4] [1, 2, [1, 2, 3], 3, 4][5, 2, [7, 2, 3], 3, 4] [1, 2, [7, 2, 3], 3, 4][5, 2, [7, 2, 3], 3, 4] [6, 2, [7, 2, 3], 3, 4]import copyc=[1,2,3,4]d=copy.deepcopy(c)print(c,d)c[0]=5print(c,d)d[0]=6print(c,d)[1, 2, 3, 4] [1, 2, 3, 4][5, 2, 3, 4] [1, 2, 3, 4][5, 2, 3, 4] [6, 2, 3, 4]a = [0, [1, 2], 3]b = a[:]a[0] = 8a[1][1] = 9print(a,b)[8, [1, 9], 3] [0, [1, 9], 3]

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