这是否是 Python 官方解释器的 bug？

[ziseyinzi]

Python 3.5.4rc1，Deepin 64 位系统。刚学 python，遇到一个奇怪的 bug，不知道是我的问题还是解释器的问题，代码如下。

L1=[1,2,1]
L2=[1,2,1]
#L2=L1
for i in range (1,3):
    L1[i]=L2[i]+L2[i-1]
print (L1)

这样执行的是预期的结果，但如果去掉第三行的注释，并把第二行注释掉，得到的结果就无法理解了。 理论上这两种写法不是等价的吗？

[kindjeff]

关键字：『 Python 不可变对象』

[TuringGunner]

不一样啊，你现在是两个单独的对象

第三行的写法，实际指向的是同一个，也就是说你改了 L1，L2 也会跟着变

[wellsc]

日经

[rabbbit]

L1=[1,2,1]
L2=L1
L2[0] = 3
print L1
// [3, 2, 1]

[lmqdlr]

当然不一样，引用类型，值类型了解一下

[LokiSharp]

'''
def a():
L1 = [1, 2, 1]
L2 = [1, 2, 1]
# L2=L1
for i in range(1, 3):
L1[i] = L2[i] + L2[i - 1]
print(L1)


def b():
L1 = [1, 2, 1]
L2 = [1, 2, 1]
L2 = L1
for i in range(1, 3):
L1[i] = L2[i] + L2[i - 1]
print(L1)

from dis import dis

dis(a)
print("==================================================")
dis(b)

2 0 LOAD_CONST 1 (1)
2 LOAD_CONST 2 (2)
4 LOAD_CONST 1 (1)
6 BUILD_LIST 3
8 STORE_FAST 0 (L1)

3 10 LOAD_CONST 1 (1)
12 LOAD_CONST 2 (2)
14 LOAD_CONST 1 (1)
16 BUILD_LIST 3
18 STORE_FAST 1 (L2)

5 20 SETUP_LOOP 42 (to 64)
22 LOAD_GLOBAL 0 (range)
24 LOAD_CONST 1 (1)
26 LOAD_CONST 3 (3)
28 CALL_FUNCTION 2
30 GET_ITER
>> 32 FOR_ITER 28 (to 62)
34 STORE_FAST 2 (i)

6 36 LOAD_FAST 1 (L2)
38 LOAD_FAST 2 (i)
40 BINARY_SUBSCR
42 LOAD_FAST 1 (L2)
44 LOAD_FAST 2 (i)
46 LOAD_CONST 1 (1)
48 BINARY_SUBTRACT
50 BINARY_SUBSCR
52 BINARY_ADD
54 LOAD_FAST 0 (L1)
56 LOAD_FAST 2 (i)
58 STORE_SUBSCR
60 JUMP_ABSOLUTE 32
>> 62 POP_BLOCK

7 >> 64 LOAD_GLOBAL 1 (print)
66 LOAD_FAST 0 (L1)
68 CALL_FUNCTION 1
70 POP_TOP
72 LOAD_CONST 0 (None)
74 RETURN_VALUE
==================================================
11 0 LOAD_CONST 1 (1)
2 LOAD_CONST 2 (2)
4 LOAD_CONST 1 (1)
6 BUILD_LIST 3
8 STORE_FAST 0 (L1)

12 10 LOAD_CONST 1 (1)
12 LOAD_CONST 2 (2)
14 LOAD_CONST 1 (1)
16 BUILD_LIST 3
18 STORE_FAST 1 (L2)

13 20 LOAD_FAST 0 (L1)
22 STORE_FAST 1 (L2)

14 24 SETUP_LOOP 42 (to 68)
26 LOAD_GLOBAL 0 (range)
28 LOAD_CONST 1 (1)
30 LOAD_CONST 3 (3)
32 CALL_FUNCTION 2
34 GET_ITER
>> 36 FOR_ITER 28 (to 66)
38 STORE_FAST 2 (i)

15 40 LOAD_FAST 1 (L2)
42 LOAD_FAST 2 (i)
44 BINARY_SUBSCR
46 LOAD_FAST 1 (L2)
48 LOAD_FAST 2 (i)
50 LOAD_CONST 1 (1)
52 BINARY_SUBTRACT
54 BINARY_SUBSCR
56 BINARY_ADD
58 LOAD_FAST 0 (L1)
60 LOAD_FAST 2 (i)
62 STORE_SUBSCR
64 JUMP_ABSOLUTE 36
>> 66 POP_BLOCK

16 >> 68 LOAD_GLOBAL 1 (print)
70 LOAD_FAST 0 (L1)
72 CALL_FUNCTION 1
74 POP_TOP
76 LOAD_CONST 0 (None)
78 RETURN_VALUE
'''

[juoyi]

注释打开后，两个变量指向同一片内存地址