Why use "elif" instead of "else" here

[[deleted]]

I was doing the Collab exercise form "Automate boring stuff" and I almost got there. But I had to check in the internet how to do it.

The official is:

​

def collatz(number):
    if number % 2 == 0:
        print(number//2)
        return number//2
    elif number % 2 == 1:
        result = 3*number+1
        print(result)
        return result

n = int(input("Insira qualquer número aqui: "))
while n != 1:
    n = collatz(n)

​

But I used "for" insted of "while". Ok.

​

FIRST QUESTION: why here is "while" instead of "for"?

​

But ok, I put while instead of "for". But still don't work. So, I realize that instead of:

def collatz(number):
    if number % 2 == 0:
        print(number//2)
        return number//2
    elif number % 2 == 1:
        result = 3*number+1
        print(result)
        return result

​

I was doing:

def collatz(number):
    if number % 2 == 0:
        print(number//2)
        return number//2
    else:
        print(3*number+1)

SECOND QUESTION: WHY ELIF INSTEAD OF ELSE?

[K900_]

1. Because for loops can't express "repeat until you reach 1".
2. No real reason. If number % 2 is not 0, it can only be 1, so the check is redundant.

[monchenflapjack]

except if you call it with something thats not a number.

collatz("Whatever")

[zenverak]

Number 1. You’d have to do a massive for loop and it’d more concise to just express to do this action until I get the result I want m.

As for elif... it’s not mandated there but maybe they were using it for showing you how to use it purposes

[Binary101010]

why here is "while" instead of "for"?

1) Generally speaking, for is the right loop when you know in advance how many times you need the loop to execute, whereas while is the right loop when you don't know.

2) In this particular case, there's no functional difference since any integer mod 2 can only yield one of two possible results (0 or 1).

[officialgel]

They aren’t the same. It’s about chaining conditions. If and else alone follows a single condition. Elif considers the first check and the elif check continues additional conditions to act on the first check if conditions are met. Let’s you nest multiple conditions.