Why does this function return "None"?

Question

def search(number, element, lista):
    if number >= len(lista):
        return "not find."
    elif lista[number] == element:
        return number
    else:
        search(number +1, element, lista)

r = search(0, 12, [2,5,1,6,8,12,24,3,7])
print(r)

Answer 1

The else branch doesn't return anything explicitly, and therefore it implicitly returns None. Add a return there and you should be OK:

def search(number, element, lista):
    if number >= len(lista):
        return "not find."
    elif lista[number] == element:
        return number
    else:
        return search(number +1, element, lista) # Here!