How to change a variable after it is already defined?

Question

I\'m trying to add or subtract from a defined variable, but I can\'t figure out how to overwrite the old value with the new one.

a = 15

def test():
    a =          


        

Answer 1

Your error has nothing to do with is being already defined… A variable is only valid inside it's so called scope: If you create a variable in a function it is only defined in this function.

def test():
   x=17
   print(x) # returns 17

test()
print(x) # results in an error.