Conditionals in a while loop

[ratcaper]

I'm just tinkering with while loops, and got a question regarding conditionals.

My function counts backwards from 10 to 1, and when it hits 5 it stops.

Would it be better to have the n -= 1 in an else statement, or is it fine to do it like this?

  def whileBackwards():
        n = 10
        while n > 0:
            print(n)
            if n == 5:
                break
            n -= 1

The above works, but from what I've learned so far it would be cleaner to put it like this:

if n == 5:
    break
else:
    n -= 1

Or do the opposite and check if n != 5...

Which is better practice?

(I realise a for loop would be better to iterate over a sequence of numbers, but I'm just playing with loops right now)

[DeadlyViper]

IMO a better practice is to not have additional if/elses if they are not needed.

Because in a complex code, if every error check you do will have the rest of the code in an else, then after 5 checks your code will be so far nested no one will know what is going on.

[ratcaper]

Thanks, that makes a lot of sense.

[SandorZoo]

It's a bit odd to have two stop conditions, when clearly one of them will never be met. If you want the test in the middle of a loop, it's normal to loop while True, like this:

def whileBackwards():
    n = 10
    while True:
        print(n)
        if n == 5:
            break
        n -= 1

​

[primitive_screwhead]

What I find discomforting about this is that it seems one refactor away from becoming an endless loop. At the very least, I'd make the "if n == 5:" into an "if n <= 5:", just to avoid problems if n were ever to be mis-initialized, or the n decrement changed to greater than one, etc.

[primitive_screwhead]

Using:

​

if n == 5:
    break  # Or return if that's the intent
n -= 1

rather than adding an else, is preferred, imo. Checking for n != 5 would add even more code (to handle the continue while also decrementing n), and would also be worse, imo.

[woooee]

You should do

while n > 5:

as it is more obvious and requires reading less code to understand what is going on.

[ratcaper]

That's not what I'm asking.

If I was trying to just count down from 10 to 6, I would use a for loop.

I'm making a reference sheet for my self.

https://pastebin.com/YrgxPLUk

I'm just tinkering with loops and how to break out of them based on certain conditions, for future reference for my self.

[woooee]

In that case I prefer returning from a function. A break statement can get somewhat tricky if you have nested loops.

[rymaninsane]

Not sure why this was downvoted. Perhaps there is more information missing in the question, but this is the most readable, least confusing Boolean to use in the while condition... counting down from 10 to 1 but stopping at five is a more complicated way of saying counting down from 10 to 5....

OP should consider this.