Python3 exec,为什么返回None?
问题描述
当下面这段代码的代码,并返回结果None 为什么?
When the code below this text, and returns the result None why?
with open('exx.py', 'rb') as file:
ff = compile(file.read(), 'exx.py', 'exec')
snip_run = exec(ff, locals())
if 'result' in locals():
print(snip_run, result)
else:
print(snip_run)
结果:
777777
None
模块代码 exx.py:
Module code exx.py:
print('777777')
解决方案
问题当然不只是print
返回None
,而是exec 返回无,总是.
The problem of course is not only that print
returns None
, it is that exec returns None, always.
>>> exec('42') is None
True
如果你需要返回值,你可以使用 eval
:
If you'd need the return value, you'd use eval
:
>>> eval('42')
42
之后您会注意到 print
仍然返回 None
...
after which you'd notice that print
still returns None
...
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