Python字典的初始化，字典参数引用传递等问题

Python字典的初始化，字典参数引⽤传递等问题# 字典初始化⽅法⼀：

1 a = {}

2 b, c = {}, {}

3 d =dict(a="a", b="b") # b = {"a": "a", "b": "b"}

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# ⽅法⼆：通过函数全局初始化

1def change():

2global a, b, c # 完全修改 a, b, c 要使⽤ global, 部分修改键值不需要 global

3 a = {"1": "1}

4 b = {"2": "2}

5 c = {"3": "3"}

6

7 a, b, c = {}, {}, {}

8 change()

9

10# 打印

11 >> a = {"1": "1}

12 >> b = {"2": "2}

13 >> c = {"3": "3"}

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# ⽅法三：通过函数返回值初始化

1def change():

2 a = {"1": "1"}

3return a

4

5 a = change()

6

7# 打印

8 >> a = {"1": "1"}

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# 错误⽅法：通过引⽤传参完全修改字典

1def change(a): # 传递引⽤参数，试图⽤新的字典覆盖原来的字典

2 a = {"1": "1"}

3

4 a = {}

5 change(a)

6

7# 打印

8 >> a = {} # 没有修改成功

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# 这个 bug 找了好久才发现，⽤ c / c++ 引⽤传参来理解 python 不完全正确