Keep a running total(budget)

[mcmxl22]

OK, I totally fudged the code so here is an update:

bal = 0.00
def budget():
    menu = ('1 Set Ballance', '2 Add Transaction', '3 Check Ballance')
    for m in menu:
        print '%s' % m
 
    what = raw_input('What do you want to do?\n> ')
 
    if what in {'1'}:
        enter = input('Enter amount.\n> ')
        print enter + bal 
    
budget()

How do I permanently change the value of bal ?

Output:
1 Set Ballance
2 Add Transaction
3 Check Ballance
What do you want to do?
> 1
Enter amount.
> 200
200.0