[英]Why running exec inside function fail in python3?
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)
是因为exec是python 3中的函数,而是python 2中的语句吗? 看看这个讨论
Python编译器在遇到print语句时将加载GLOBAL,在该处,它作为未定义变量'A'失败。 如果您尝试反汇编代码[import dis],则将看到后端流程调用的执行情况。
本文在python 3中的函数中创建动态命名的变量/在python 3中了解exec / eval / locals中给出了一个很好且定义明确的解释
如果您确实希望execfunction
在全局范围内执行该函数,则可以执行
def execfunction(code):
exec(code, globals())
然后,这将使对execfunction
调用在全局范围内执行,而不是仅在函数的局部范围内执行。
供参考: https : //docs.python.org/3/library/functions.html#exec
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