[Tutor] Valid Username Program

[Richard Damon]

On 10/8/20 7:29 AM, Aliyan Navaid wrote:
>    def valid_username(username):
>
>        if len(username) < 3:
>
>            print("Username must be atleast 3 characters long")
>
>        elif len(username) > 15:
>
>            print("Username is too long")
>
>        else:
>
>            print("Valid Username")
>
>     
>
>     
>
>    Dear Sir,
>
>    So this program checks the validity of a username.
>
>    I wanted to ask that instead of elif, I could’ve written another If
>    statement in this program right ?
>
>    And can you please also explain that when to use elif statement and when
>    to use multiple if statements.
>
If the elif had been an if, then the final else would be run for any
username <= 15 characters long, even if they are <3 characters long
(those would print:

Username must be at least 3 characters long

Valid Username


The key here is that an if / elif / else chain will only run exactly one
of the following code sections, but with if / if  / else the final two
are not eliminated by the success of the first.

-- 
Richard Damon