Python, “print” and “return” resulted in different boolean logic

I recently started learning python through Sololearn and got to Recursion. To get better understanding of the code, I simplified it to:

def is_even(x):
    return x
def is_odd(x):
    return not is_even(x)
print(is_odd(2))

The return not is_even(x) is boolean and will resulted it as False and when it passed to the def is_even(x): it still would return as False. However, when I change the return x to print(x)

def is_even(x):
    print (x)
def is_odd(x):
    return not is_even(x)
print(is_odd(2))

The result would be:

2
True

How did this happen? What is going on between the return not is_even(x) and print (x). Thank you

Answer

Maybe this will get you on track:

def returning(x):
    return x

def printing(x):
    print(x)

returning(2)
# 2

printing(2)
# 2

a = returning(2)
a
# 2

b = printing(2)
2
b
# None

The difference is that return returns a value from a function which can be used to pass to another function / variable. print just prints out the information but does not return any value, this is why b holds no value, but during the assigment b = printing(2) it immediately printed out what was passed to it, when a = returning(2) did not, it assigned the value to variable a.

And None is falsly in python.

None == False
# False

None == True
# False

not None == True
# True

What you are lacking is for is_even to return a bool instead of the argument passed:

def is_even(x):
    return x % 2 == 0
def is_odd(x):
    return not is_even(x)

is_odd(3)

# True