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

# All the mumbo jumbo aside, here is an experiment 
# to illustrate why this is something useful 
# in the language of Python:
a = 15    # This could be read-only, should check docs

def test_1():
    b = a + 10    # It is perfectly ok to use 'a'
    print(b)

def test_2():
    a = a + 10    # Refrain from attempting to change 'a'
    print(a)

test_1()    # No error
test_2()    # UnboundLocalError: ...