Pitfall12 recursive

def get_input():
    my_var = input('Enter "a" or "b":')
    if my_var !='a' and my_var !='b':
        print('You did not type "a" or "b". Try again.')
        get_input()
    else:
        return my_var
    
print('got input:', get_input())


def get_input():
    my_var = input('Enter "a" or "b":')
    if my_var !='a' and my_var !='b':
        print('You did not type "a" or "b". Try again.')
        return get_input()
    else:
        return my_var
    
print('got input:', get_input())


so while the recursion does happen, the return value gets discarded, and then you fall off the end of the function. 
Falling off the end of the function means that pyhton implicitly return None, just like this:

def (x): 
  pass
print(f(2)) ---> None

-----------------------------------------------------

# in which the recursive calls misses a return. It thus evaluates to None whenever it recurses.

def recurse(n):
    if n == 0:
        return "Done"
    recurse(n-1)   # missing return

print(recurse(5))  # prints None
---> 
None