Python——Something about exec()

Asked Feb 12 '21 at 10:35

Active Feb 12 '21 at 10:40

Viewed 27 times

def function():
    exec('a=2')
    print(vars())
    print(a)
function()

a=1
def function():
    global a
    exec('a=2')
    print(vars())
function()
print(a)

Above: The output was {'a': 2}, but then the error message said name 'a' is not defined.
Below: I still got {'a': 2}, the a outside was still 1.

Well, what's the difference between a = 2 and exec('a = 2')?

edited Feb 12 '21 at 10:40

asked Feb 12 '21 at 10:35

SkyLian

Check the second and third parameter of [`exec`](https://docs.python.org/3/library/functions.html#exec). Example: `exec('a=2', globals())` – Matthias Feb 12 '21 at 10:39
4

The solution to nearly every problem with exec is "stop using exec". – khelwood Feb 12 '21 at 10:44
How fool I am! Thanks! @Matthias – SkyLian Feb 12 '21 at 10:46
Anything bad with exec()? @khelwood – SkyLian Feb 12 '21 at 10:47
[Why should exec and eval be avoided?](https://stackoverflow.com/q/1933451/3890632) – khelwood Feb 12 '21 at 10:59
I could explain what you had to do to make it work, but I must admint that I never used `exec` in over 15 years of Python programming. – Matthias Feb 12 '21 at 15:23
@Matthias Sounds like exec() is really a trivial function. – SkyLian Feb 15 '21 at 03:26
Sounds like I've already had a lot of programming experience and knew which evil language features to avoid. :) – Matthias Feb 15 '21 at 10:56

Python——Something about exec()

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