参考了这个问题,然后解决了。
嵌套函数获取调用函数

用全局变量 global 可以实现

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()

函数外加引用, 这是变量作用域的知识

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

或者把a,b放一个字典变量里, 这样就不需要global了

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