python - How to get value in nested function

Question

Suppose there is such a piece of code:

def demo():
    a = 1
    b = 0
    c = a / b

def main():
        try:
            demo()
        except Exception as e:
            print(e)
main()

Now we hope that the values ​​of a and b in the demo can be obtained without making any modifications to the code in the demo function when an exception occurs.

Answer 1

Referred to this problem and solved it.
Nested function gets calling function

Answer 2

Can be achieved using global variables global

a = b = 0
def demo():
    global a, b
    a = 1
    b = 0
    c = a / b

def main():
        try:
            demo()
        except Exception as e:
            print 'a: %d, b: %d' % (a, b)
            print(e)
main()

Answer 3

Function plus reference, this is the knowledge of variable scope

a = None
b = None
def demo():
    global a, b
    a = 1
    b = 0
    c = a / b

def main():
    try:
        demo()
    except Exception as e:
        print(e)
main()

print a
print b

Or put a and b in a dictionary variable, so that global is not needed

g = {"a":0,"b":0}
def demo():
    g['a'] = 1;
    g['b'] = 0
    c = g['a'] / g['b']