Hi, welcome to this new video. We are going to start
talking about iteration. And this is one of the kind of, the
cornerstones of, one of the things that we can do with programming is basically
repeating things over and over and not necessarily repeating
them exactly the same. But rather kind of how it can repeat and learn from every iteration
that we perform, right? So let's start understanding
the notion of iteration. We're going to be understanding the notion
of iteration as a sequence, right? So think about a sequence of
instructions for the code to be repeated a specific number of times to
achieve a particular result, right? As you saw in our last video, we were starting to understand primitives
that have a sequence of vertices, right? So you might be thinking, well, it's kind of quite manual to type those
vertices over and over and over again. What if I want to have 1000 vertices,
right? So it's clear that many
operations within computing between programming need to
be performed automatically. Or need to be displayed in such a way
that the computer would understand how to iterate or
go through a large amount of data or repeat something perhaps many many times,
right. So that's something that is actually
quite easy to do with specific constructs that we have for that. So we're going to be introducing
something called the for loop. A for loop is our first out of a few
different loops that we will evaluate, but the for loop really gives
us a simple way to iterate. So let's look at the syntax together. So it says four and we have a variable which is in this
case num representing a number. And then we use in range, range is going to give us
a series of numbers, right. We saying four,
because we want a range between 0 and 3. One of the things that we actually
will see within this kind of range function that we're using
is that we will start at 0. 0 it's by definition especially or
by convention in a way, the way we're starting
an iteration process. And you can see as we run this code and
we're using here an indentation in python. The indentation meaning the space
that is granted below the for loop, will suggest that all
the lines after the for loop that are indented belong to that for
loop, right? It's a series, it's a part of the code that specifically
will be repeated many times. And why do we need this variable of num? Because we want to keep track
in which iteration are we in so many times we can think of it as
a variable I standing for iterator, right. Because the first time we
loop through this variable, the variable will start at 0, and then we will move to the second loop
version of the loop, and it will be one. The third time will be two, and
the final time would be three, rihgt. And at that point we will conclude
the loop, because the variable is no longer within the range that we've
specified and we can continue our code. So whenever you see this kind
of structure, the for loop, think of it as a section of the code
in which the program will repeat itself until it concludes the task
established by the loop, right? So let's look at an example. We can look at something like a tuple,
like we haven't really kind of described data structures yet,
we're going to look that later. But if you have something like a series
of words together, like hello world, you can do a loop that evaluates each one
of the entities within that structure. So hello world, there are two
strings separated by a comma. So if we would actually print
each one of the entities within the hello world,
or the words within that, you would get first the line hello and
then the line world. Similarly, we could actually
loop through a string, right? So strings are a collection of letters,
and we could also think, well, what if we want to iterate
over each one of those strings? So in this case,
this example, the variable I, which again is an arbitrary name
that we're giving to this variable. Will select independently the different characters that exist within
the string hello, right? So as you can see,
the result of such print function, you would get the h, the e,
the l, the l, the o, right? So for loops are used in a variety
of contexts to repeat information, to go through information and
repeat some operation. We can do a large part of our code
within a loop structure, right, where we do kind of complex calculations. And we will start seeing that loops,
a very quick way for a computer to really start running, maybe slower and start kind
of using a lot of computation, right? But that's the nature of what
we can do with computing. How many things can we really
evaluate at a given frame? And are we doing those sequentially or
are we doing those distributedly? That's different paradigms of
programming than we might take. In this case, the for loop suggests that we will actually do
a repetition in a single frame, right? So within a single frame
of our computation, we will perform a series of calculations. So this is the foundation of our for loop. In the next videos, we'll start seeing
how to use them within processing.