动态变量名

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最近的代码设计中, 需要用到动态变量名, 在此记录下
以下代码在win 10, python3.6版本下通过验证

In [1]: for i in range(4):
   ...:     exec(f'val{i} = {i+1}')
   ...:
In [2]: val0
Out[2]: 1

In [3]: val1
Out[3]: 2

In [4]: val2
Out[4]: 3

In [5]: val4
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-5-dd17f4ed2c2a> in <module>()
----> 1 val4

NameError: name 'val4' is not defined

以上用法可以通过,但是把它放到函数体中就会报错:

def test():
    for i in range(3):
        exec(f'val{i} = {i}')
    print(val0)
    print(val1)
    print(val2)
test()
#output
Traceback (most recent call last):
  File "D:\datawork\ti\apps\temp_scripts\test.py", line 132, in <module>
    test()
  File "D:\datawork\ti\apps\temp_scripts\test.py", line 129, in test
    print(val0, end='-----\n')
NameError: name 'val0' is not defined

解决办法是使用locals()或globals(), 使其变为局部变量或全局变量:

names = locals()
# names = globals()  这个也是OK的
def test1():
    for i in range(3):
        names[f'val{i}'] = i
    print(val0)
    print(val1)
    print(val2)
test1()
# output
0
1
2