In recursion, what does this statement mean..'return not'?

Question

Here is a code:
def is_even(x):
if x==0:
return True
else:
return is odd_(x-1)

def is_odd(x)
return not is_even(x).

print(is_odd(17)) yields True.

Now,i understand the whole code till the point of 'return not'. What does it mean exactly? And how is it related to the output?

Answer 1

I've done extensive handtracing on this. In case you need it.

https://www.sololearn.com/Discuss/1333646/?ref=app

Answer 2

not inverts a boolean
True -> False
False -> True

Answer 3

Because it returns a boolean, return not will return opposite of it's boolean it returns. if
is_even(x) returns False, not converts it to True and vise versa.