[Tutor] returning None from function definition

[Mats Wichmann]

On October 24, 2020 12:24:16 AM MDT, Manprit Singh <manpritsinghece at gmail.com> wrote:
>Dear Sir ,
>
>Consider a problem :
>WAP a program that accepts two integers as user input from keyboard (a
>and
>b), and then prints all prime numbers within the range(a, b+1).
>
>def prime(x):
>    if x < 2:
>        return None
>    else:
>        for i in range(2, int(x**0.5) + 1):
>            if x % i == 0:
>                return None
>    return True


Consider if you decided to annotate this function, because you want to be clear about the intent.  What would you write?

def prime(x: int) -> bool:

would be a declaration that the return is a boolean. If you now run one of the host of checkers available, it would complain that in two places the return type is not expected.  Here's a case where the type checking actually can be a bit useful. 

-- 
Sent from a mobile device with K-9 Mail. Please excuse my brevity.