All language subtitles for 16. While Loops 2

So when should you use a while loop and when should you use a for loop.

And it really depends on the problem you're trying to solve.

For example in a for loop I could do four item in let's say a list.

One two three.

And just looking at this code you know right away that it's going to be looped over three times.

Right.

And I could say here print item but he can do this in a while loop as well.

I can say I equals to zero.

And then while I is less than let's say the length of the list that is one two three well in that case

I want you to print I or the item and then increment I by 1 if I run this I see that.

Well technically here we're incrementing the eye which is the value but let's say we had a list up here.

So my list and this list will be 1 2 3.

Well my list can be iterated with a for loop or can be iterated with a while loop and we simply say

my list at index of I and if I run this I get the same results.

But which one do you think is better first off while loops are very flexible.

We can do a lot because we have this conditionals team and we can loop more than three times if we really

wanted to.

So in that case while loops are more powerful but for loops are simpler.

Right.

Like this code reads it really nicely and really well it makes sense.

We just want to loop over something that we already know how many times we want to loop over three times

with a while loop.

We have to create this variable and we have to make sure we remember to increment the variable so we

don't get an infinite loop so with a while loop you need to make sure we remember to halt the loop at

some point.

So my rule is usually this for simple loops or iterating over editable objects for loops are great but

let's say you're not sure how many times you want to loop over something you're not really sure how

long it's going to take for looping.

So you want to say while something is true just keep looping.

For example let's say we're trying to go through an email list that we've collected on a Web site and

for each email list we want to send an email.

Well while the list is still there let's just keep sending emails.

There are many many cases but one of the most useful ways to use the while loop is like this.

It's to say while true do something and make sure that at the end we break hold on.

What's happening here.

I'm saying while true wouldn't that create an infinite loop.

I mean true is always going to be true and you'd be right if you noticed that.

But again we have a break statement here.

So at the end after rerun line 3 it's going to break but now we can do something powerful like input

here.

And if you remember an input is going to ask us for a prompt to enter something so I can say hey input

say something and if I click run it's going to say Hey say something you know let's add semicolon here

or call in here and illustrate that again and look at that it's saying Say something.

I'm on line 3 right now.

So I'm going to say hi

and just see that we just broke out of the loop.

It only asked me once.

Even though this was true as soon as we got to line four I was done.

But what if I remove this and I click run if I say something I say hi.

And then in asking me again.

Hi hi I'm telling Hi.

And it keeps asking me asking me asked me.

And we have an infinite loop.

But the interesting thing here is that we can use conditional logic right.

What if we said response here and collect whatever the responses and say if the response is equal to

let's say by then I'm going to break so that if I run this again I say hi.

Keeps asking me and you know what I'm getting annoyed with you machine I'm going to say bye.

It's going to exit it out for me.

How cool is that.

So while loops are extremely useful for tasks like this where looping can happen for a long time you

don't know how many times it's going to happen.

But this is something that you're just going to have to get used to with practice eventually.

And I promise you this happens where you'll figure out when to use while when to use for loop but at

the end of the day use whatever solves your problem.

I'll see in the next one by.