为什么在python3中运行exec内部函数失败？

Question

运行python3代码的结果：

------- input option 1 - exec code is executed --------
0 - for running inside function, 1 - for running in main programa: 1
option = 1
10

------- input option 0 - exec code not executed inside function ----
0 - for running inside function, 1 - for running in main programa: 0
option = 0
code inside execfunction => A = 10
Traceback (most recent call last):
  File "myexec.py", line 19, in <module>
    print(A)    
NameError: name 'A' is not defined
---------------------Code --------------------------

myexec.py

def execfunction(icode):
    print('code inside execfunction => %s' %(icode))
    exec(icode)

option = int(input("0 - for running inside function, 1 - for running in main programa: "))

print('option = %d' %(option))

code = 'A = 10'

if (option == 1):
    exec(code)
else:
    execfunction(code)  

print(A) 

Answer 1

Python编译器将在遇到print语句时加载GLOBAL，其中它作为未定义的变量“A”失败。如果您尝试反汇编代码[import dis]，您将看到后端进程调用的执行

本文给出了一个很好的解释 Creating dynamically named variables in a function in python 3 / Understanding exec / eval / locals in python 3

Answer 2

是因为exec是python3中的函数，而不是python2中的语句吗？ Have a look at this discussion

Answer 3

如果您真的想execfunction在全局范围内执行函数，您可以这样做

def execfunction(code):
    exec(code, globals())

然后，这将使对execfunction的调用在全局范围内执行，而不是只在函数的本地范围内执行

供参考：https://docs.python.org/3/library/functions.html#exec