So, did those problems take a while?

I feel like the while-loop is a bit of a simpler concept than the for-loop,

probably because it's just a condition with no variable or iteration needed.

Let's look at how I solve these problems.

The first problem, heating the oven is a pretty normal use case for

a while-loop, so we'll say while current_oven_temp < 350.

So as long as it's under 350, we can go ahead and increase it, right,

so current_oven_temp + = 25, and then print current_oven_temp.

Now, you could do these in either order depending on how you read

the instructions.

Maybe you feel like you should print it before you increase it or

increase it before you print it.

It really doesn't matter though and if it's not less than 350,

so this would be where else comes in, then we want to print out, the oven is ready.

Now, we could do this without using the else, but

I like to include them as it makes it a bit more obvious what's going on.

So let's go ahead and test this one, so we'll do python while.py.

And we can see we've got 100, 125, 150 and so on, until we get to 350 and

then the oven is ready.

Great, so it looks like we're getting all those intermediate degrees.

Onto problem number two.

Okay, so the first thing that I have to do is have an infinite loop.

So I'm gonna go ahead and do while true, which is a loop that will never end.

You could also do say while one, or while a, or

anything that's always going to evaluate as true.

So then I'm gonna ask for a number.

Now, I'm gonna go ahead and I'm gonna lowercase it, which, of course, won't have

any effect on the numbers, but it makes the queue comparison a little easier.

So I'm gonna say, num = input.

And i'm gonna say, give me a number or q to quit,

and then I'm going to call lower on that.

All right, so now let's do that comparison.

So if num == 'q' then break.

Now, I'm gonna use break here to immediately end the while-loop.

Now, like I said,

you could do this without the break, but I like to have the break in there.

Okay, so now, let's try to turn it into a number,

to be a bit more flexible, I'm just gonna turn them all into floats.

But you could make whatever decision you want here, if you wanna make them ints,

floats, whatever, as appropriate.

So I'm gonna do, try: numbers.append(float(num)),

the float version of the num.

And then the exception that I'm going to catch is, ValueError.

And if the ValueError comes up, then I'm gonna do, continue, so

I'm just gonna start that loop over again, okay?

So if anybody gives me something that's not a number and it's not q,

then we're just gonna ignore it.

We're gonna pretend it didn't even happen and we're just gonna go on to the next

step of the loop, which comes right back to the input, all right.

Now, I could leave out the continue, I could put in, say, pass instead.

They're effectively the same in this case, but

continue is like the more obvious thing.

Okay, so now, we're done with the loop's code.

Because at this point they have either, they've even wanna put in a new number, or

they've give us a q and they wanna quit.

So, I can't use the else here that I would normally have used, because this

break counts as the loop ending early and so, that makes it skip the else clause.

So I'm just going to do the code that I wanted to do here.

So I'm gonna print out you entered, That, and then the numbers that they entered,

and then I will print out the total is, and then the sum of the numbers.

And sum, if you haven't heard of this function before.

We'll take a list of numbers, and it will add them all together,

and then I will print, the average is, and

then we will print sum(numbers)/len(numbers).

And all right, so now that should do it.

So this is gonna call total_and_average for us, so

let's go ahead and python while.py.

Give a number, okay.

So, let's do 5, 5, 5, and 5, and then let's do a queue.

So we entered 5, 5, 5, and 5.

The total is 20 and the average of that is 5, cool.

So that's handy I guess, depending on your needs for calculating averages and sums.

Okay, so now, let's try problem number 3, this is our last problem.

Now, this one needs us to skip over numbers that aren't evenly divisible by

three or five.

Now, initially, I was thinking that I'd want to use continue on this, but

there's really no reason to.

Much like problem number one, we need a condition in our loop.

So we're gonna say while current > 101.

Then we'll check the division, or divisibility of the number.

Now to do this,

I'm going use the modulo operator, which returns the remainder from division.

So, if not, current % 3, or

current % 5 == 0, then print(current).

So you probably don't wanna do this exactly like me.

I'm showing you deliberately two different ways of testing this right now.

You pick which ever one's more obvious to you.

So first we have the not current % 3, and

this one will evaluate the true if the remainder is 0.

Because 0 is falsy and the not swaps it.

So instead of being falsy, it becomes truthy because of the not,

and then the current % 5 is equal to 0.

It should be pretty obvious, but we're comparing to see if when I do modulo of

modulo 5 against current if that comes out to 0.

So if so, that becomes true.

So if this is true or

if this is true, if either one of them is true then print out the current number.

Now, finally, we need to increment the number.

So move up to the next number, and that should do it, let's test that out.

So python while.py, now, I'm gonna get asked for a number.

I'm gonna put in a 1 and q, and then we get our numbers in here.

So like 99 is divisible by three, 96 is divisible by three, 100s divisible by 5,

90s divisible by three.

But we're not getting like say 82 which isn't divisible by 5 or 3.

So awesome that's all of our numbers.

Thanks for practicing loops with me.

Hopefully, this will help you get

more comfortable with these super useful constructs.

Be sure to let us know if any other topics that you'd like to see a bit

more practice on.