How to change variables in functions (python)

Question

When I make a code like:

n = 0

def add_1 ():
n += 1

print(n)

It would give an UnboundLocalError.

How do I fix this?

Answer 1

You need to call the function, which needs a parameter and should return a value. This works:
n = 0
def add_1(n):
n += 1
return n
print(add_1(n))

Answer 2

You can also add a global declaration in the function before using it.
global n.
However in real world programs usage of global variables is discouraged.