How can I make a recursive function in Python return a value instead of None?

Question

I have this function that should return 1 once the input is 'x'. Why does this return None if the first input is 'y' and then the next input is 'x'?

def func():
    a = input('x or y\n')
    if a == 'x':
        return 1
    else:
        func()

print(func())

This is written in the command line:

x or y 
y         # My input
x or y
x         # My input 
None

Why does it return None and not 1?

write ``return func()`` in the ``else`` block. as for the "why" - every function in Python has a return value. If you do not set it explicitely, it will be ``None``. — Mike Scotty, Oct 19 '18 at 09:48
@MikeScotty- In Python 3.6, his/her code is working fine without `return` in else block. — shaik moeed, Oct 19 '18 at 09:56
@shaikmoeed did you try exactly as OP posted? First enter ``y`` and then ``x``? Or did you enter ``x`` on the first go? — Mike Scotty, Oct 19 '18 at 09:57

score 0 · Answer 1 · answered Oct 19 '18 at 09:51

functions always give output next to the return statement. You need to return your function as output for recursion.

def func():
    a = input('x or y\n')
    if a == 'x':
        return 1
    else:
        return func()

print(func())

will make your function recursive. Best regards...

score 0 · Answer 2 · answered Oct 19 '18 at 09:52

In the else statement you are calling the function but not returning from it. So the function returns none if it goes in the else statement.

def func():
a = input('x or y\n')
if a == 'x':
    return 1
else:
    return func()

print(func())

Writing it like this will fix the problem as you'll return the calculated value from func. And the function will always return something regardless of the input.

How can I make a recursive function in Python return a value instead of None?

2 Answers2