Okay, welcome to this new video. I'm excited to share with you
the notion of nested loops. And nested loops are a bit
of a tricky concept, but let's just break it down together and
see what it means, right? So the idea of a nested loop is that
you could actually use a loop within a loop, right? Meaning that you have a for loop or
any particular kind of loop, and within that you can create another one,
right? You might be wondering,
why is that necessary? Well, there are certain constructs,
like a grid, for instance, that makes sense to be thinking of
it as a loop within a loop, right? For any number of rows, you have
a certain number of columns, right? And so we'll see examples
of how that works, right? But for that first, let's just
create a bit of a definition and understanding that we have something that
we would call the outer loop, right? Which is the first loop that
we basically describe, and then within that we would
have an inner loop, right? Let's see an example of how
those two loops would actually work with each other, right? In this particular example,
we have a variable, i, that represents the outer loop
that goes between 1 and 3. So we have the number 1 and 2, right? As you can see on the top, and the j
variable, which is a convention that we tend to use whenever you have
a nested loop, you use I and j. This is, again, up to you but
you could use x and y. But you'll see i and j kind of quite regularly within code that
other people might use conventions, right? So the j variable goes from 4 to 7. So we have 4, 5 and 6. So let's see, what would be
the execution of the print function that prints at every stage of the loop i,
j, right? And the diagram that you can see
on the right represents that i initially will be stuck at 1, right? So I will be 1. So we would initially print 1 and 4, 1,4. We would stay with one and
iterate over the j, right? I mean, the inner loop will be iterating. So we're going to have 1,5 and
continue to iterate over j. And we're going to have 1, 6. Once we finish with the inner loop, we're
going to go back to the outer loop, right? And we're going to move
the outer loop to 2. So in this case we have 2, and then we
go back to the inner loop once more. So we're going to have 2,4,
2,5, and 2,6, right? So it's important to understand that
the final sequence that you're going to end up is 1,4, 1,5, 1,6,
2,4, 2,5, 2,6, right? That's the order in which those
loops are going to execute, right? You basically freeze the first loop
while you execute the inner loop first. Then you move to the second
iteration of the outer loop and you execute the inner loop first. So it might be a concept that is
more easy to kind of grasp as we use it within the code and
we see some kind of graphic examples. So we're going to do
that in the next video.