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So now that we've actually installed and
configured Python and set up IntelliJ,

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it's time to start talking about and
using Python.

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First I wanna give you a little
bit of an introduction of Python.

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Now it's actually an object
orientated interpreted language.

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And really it's quite easy to
use in terms of other languages.

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And also runs on a lot of, many operating
systems, including Mac, Windows,

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Linux, and quite a few other ones as well.

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It's interesting, it's actually
named after the cult comedy show

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Monty Python's Flying Circus,
but [LAUGH] not after the snake.

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And you'll find actually various
references to Monty Python's sketches in

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the official documentation.

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The good thing about Python is that it
supports a lot of basic data types,

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such as numbers and strings.

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But also, it supports more complex types,
like lists and

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dictionaries, that can greatly
simplify data processing.

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And you'll find out more about that, and

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about those data types as
you move through the course.

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As I mentioned it's object-orientated,
so it does support that fully and

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allows multiple inheritance, which may be
nothing to you at this point in time, but

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believe me, it's a good feature, and

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you'll be learning about that
through the course as well.

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The other thing is that the data
in Python is strongly typed, so

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what I mean by that is for example,
if you attempt to add a number.

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And a string, you'll actually get an
error, but it's also dynamically topped,

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so you're free from worrying
about variable declarations,

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and again I'll be explaining that
fully as we go through the course.

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Now despite the fact that it's quite
easy to use, it's also very powerful.

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Interestingly enough, it's one of the
three official languages used to Google.

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Now the creator of Python, Guido van
Rossum, hope I got the pronunciation

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correct, he actually worked for
Google for over seven years and

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he was actually allowed to spend half his
time developing Python while he was there.

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Now one important consideration
before we get into the code, and

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I promise you we are getting into the code
is that the Python team decided to break

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backwards compatibility
when they created Python 3.

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So while it's very similar to Python 2,
and

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a lot of programs will work in Python 3,
there's no longer any guarantee

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that Python 2 programs will actually
work with the Python 3 interpreter.

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And the other thing to
know is that there's no

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further development
happening with Python 2.

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So in other words, version 2.7
of Python is the final version.

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But with that said, they're gonna continue
to support it until at least 2020.

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But, it's really for that reason that
we chose Python 3 as the way forward.

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And a lot of the code is going to work
okay for python 2, and many systems

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are running it, but there are differences
as you'll find in version 2 and version 3.

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So as they come up, we'll actually talk
about those differences in this course, so

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you can come away with a good
understanding if you are in the situation

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of having to get to the tricky part of two
code working after completing this course.

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Anyway enough with the introductions.

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Let's get into actually
creating some code.

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So have your InteliJ open.

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So we're gonna create a new project now,
so

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we can start playing around with Python.

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And to do that I'm gonna
click on Create New Project.

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And if you recall in the previous video
I actually configured the project SDK.

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So that we were able
to start using Python.

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So, that's configured.

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So make sure you're selecting Python
as the type we're going to be using.

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The project type.

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Click on Next.

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I'm not gonna click on
any of those options.

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I'm gonna leave them as the defaults.

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Click on Next.

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And next I need to know the folder
where I'm going to be putting my files.

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And what I'm going to do is create
a new folder structure to put all my

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Python code.

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I'm gonna click on these
three little buttons here.

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And I'm gonna click on a folder that
I've got from my various courses and

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I'm gonna click on PythonPrograms.

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So, that's my new folder that I'm going
to be creating all my projects in.

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And each time I create
another Python program,

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I'm gonna put it in it
s own separate folder.

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And notice when I did that the first time,

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IntelliJ doesn't quite get
this right cuz it's assuming,

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by the actual path that I created,
that that's what I wanna call above.

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What I need to do is actually delete
that and we'll call it HelloWorld.

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It's gonna be our very first program and
what I'll need to do is because I'm

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actually in here, I need to
actually type in HelloWorld there.

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So in other words,

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the path is Programs/PythonPrograms and
the project is HelloWorld.

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And what will happen is IntelliJ
will create that new folder for

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us automatically.

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Now, depending on whether you got this
button or this option clicked down here,

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that may be open or close, these
are the options that may come up, but

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you can safely ignore all of those.

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The main thing is the project location,
where you wanna save your files, and

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the project name.

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Again, this doesn't really matter to
this day, but we're gonna go ahead and

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call it HelloWorld.

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So we're gonna click on Finish.

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And IntelliJ will come and say,
do you want me to create that folder?

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Well, that's yes,
we do want you to do that.

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So I'm gonna click OK.

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And actually create it for
us and IntelliJ will open up.

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And what I'm gonna do is go
into presentation mode, so

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it's easy for you to see what I'm typing.

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And the other thing to do which, note that
IntelliJ has selected that anyway, but

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make sure that project view is selected.

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That's the easiest one to never get
through your various false trackers that

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you'll need to do doing this course.

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So I'm gonna click on that and
I'm gonna open this up.

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And we're actually ready to go.

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So what we're gonna do first, we're
gonna go and create a new python file.

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So we've created a project, and a project
can contain a number of different files.

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We're gonna create a python file, so
we can actually type some code in.

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So to do that, we're gonna click on,
go to the File menu.

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Click on New, and then select Python File.

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And notice that the kind is
automatically selected, python file.

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We're gonna type in HelloWorld.

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And we're gonna go press Enter or
I'm gonna click OK.

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>> And
we've now got some code on the screen.

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So you notice that in line 1,
IntelliJ has added that automatically.

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It's added the username for
the particular machine that you're on.

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So you can safely ignore that.

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That'll be added automatically.

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So let's actually put some code in.

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And we'll start off with the hello world.

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So we're gonna type in print.

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Which is a command to actually type or
to display something on the screen.

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And you notice as I'm typing
IntelliJ's actually coming up and

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giving us some options.

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So if I go back and
start to just type the letter p,

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we've got quite a few options there.

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And if I start typing,
the more I type the more,

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sort of filtered the list
of options come up.

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So eventually I've got
the exact command I wanna type,

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in this case it's gonna be print.

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So IntelliJ does do a lot of this work for

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you in terms of trying to figure
out what you're trying to do.

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And you don't actually have
to type things in full.

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If you're happy that that's the correct
option, you can just press Enter.

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And it actually fills in,
does the rest for you.

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The other thing is, you might be looking
at those green little messages appearing

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down the bottom of the screen,
you're wondering what they are.

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I've actually setup a special plugin for

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IntelJ to show you
the keystrokes that I'm trying.

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So you won't be seeing that when you're
actually this on your computer but

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it's there to help you out in case
you run another operating system and

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you wanna know what keystrokes
I'm actually pressing.

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So moving forward,
I'm going to type in Hello World.

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And to print we use single quote,
we just type hello world,

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like so, and we're ready to go.

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That's literally,

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that's probably the easiest Python
program you'll ever actually write.

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So you've got a couple
of options here now.

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To run it, we can actually
come up here and click on Run.

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Go to the Run menu and select Run.

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You can also here,
you can actually right-click,

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and we can actually click
on Run there as well.

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So it's really your personal preference
as to which way you wanna do it, so

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I'm gonna click on Run.

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And we notice that unsurprisingly,
little more space here.

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All our words are actually
shown on the screen.

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Now the other thing I wanna point out is
that you can actually choose where you get

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this little window,
this little Run window to appear.

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You may want the Run window for example
to appear down here, down the bottom,

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instead of to the right.

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I personally I prefer it to the right but
it is entirely up to you.

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And if you wanted to change locations you
could come over here to this little cog,

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and you can click on that and
you can actually move two,

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and choose the location.

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So I've currently got it selected to
the right, which is why right isn't a menu

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option, but if I select bottom,
I get the little run menu down the bottom.

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So it's a personal preference as
to which way you wanna go there.

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And if you wanna close the window,
you can actually press X as well and

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that actually closes the window down.

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And we'll be going through some of the
other various features of IntelliJ as and

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when needed.

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But probably the important one was
the Run menu that I actually showed you.

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When in doubt, there's lots of shortcuts
that you can learn in IntelliJ.

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And you can come up to the various menus
and when you click them you get various

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options as to the shortcuts and
what the actual commands do.

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And you'll be finding that there's
lots of different shortcuts that

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are built into IntelliJ really to
make your life easier as a developer,

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and I'll try and show you some of
those as we go through the course.

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Some of the shortcuts for
example with the project menu.

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I can hold down command and

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press 1 and you notice down in the bottom
it says Alt+1 for Windows or Linux.

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Press it again and
it actually shuts it down.

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So I haven't got that window there now.

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I can press it again to bring it back.

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And you can do the same for
a lot of the different windows.

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Tools > indows, these various windows, we
noticed before when we were running we had

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command four, that's not activated
now cuz it's not running.

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But that's how you open a window or
you can close a window.

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Anyway, getting back to the code.

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Now although this is really probably one
of the simplest programs you can actually

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write, there are actually a few
important basics to understand here.

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So firstly,
we've used the Python function for print.

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So Python, like many other programming
languages, has got many mathematical

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functions, like round, to round the number
of digits after the decimal point,

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char and ord, to convert characters
to the numerical representation,

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and vice versa and
many more that are built in.

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But you can also actually define your
own functions as you'll see later in

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the course as well.

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So to tell the print function
what you'd like printed,

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you provide a value in parentheses as you
saw there, as you saw me put Hello, World!

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in parentheses.

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Because we're using a string, we actually
have to put a single quote to the left and

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to the right of the string to tell
Python that this was a string.

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But we can also put in numerical
numbers if we want it to actually

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be computed by Python.

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For example, I can type in print 1 + 2 and
do a couple here.

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Print 7 * 6.

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We can do a print without
any parameters whatsoever,

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and which won't print anything.

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And we could actually print the end.

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And if we actually run this now.

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Again, I can right click
that I wanna run it.

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Down at the bottom you can see
hello world, for the first line,

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which we saw in the previous
time we ran the app.

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Print 1 + 2,
now to three there as you can see.

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Print 7 * 6, which is 42.

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And you notice print in
parenthesis without any primers,

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in other words, with nothing in there.

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Print in the blank line and
of course using the string again, the end,

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and surprisingly printed the end.

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So in regards to strings, strings
can be enclosed in either double or

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single quotes.

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So you saw that in the first example,
there had a single quote.

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But down here at the end
I used double quotes.

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So, Python doesn't mind which one you use.

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You can use either, but if you want to
include a single quote in a string you

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normally want it to surround
that in double quotes.

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What I mean by that is I can put something
like Python strings are easy to use.

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And that works okay because we've
got double quotes surrounding it and

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we can also do something like this.

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If we wanna use a double quote,

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then we can even include quotes and
strings.

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So basically if you wanna
use a particular a single or

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double quote, use the opposite quote
to actually create the string.

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To unlock other languages like Perl for
example,

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there's no difference between
using single or double quotes.

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So Python doesn't make any
distinction between those.

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That said,

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if you start a string with one type, then
you must finish it with the same type.

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So if you need to include
a single quote in a string,

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then use double quotes to enclose
a string like I mentioned.

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Similarly, if you wanna
include double quotes,

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then close the string in single quotes.

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The other thing you can also do
is you can concatenate strings.

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So in other words,

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you can make a string longer by
actually putting two strings together.

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So the way we can do that is we
can type print("hello" + World.

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So, that's actually a distinction
to this previous line here,

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where you've got one big stream.

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We've actually created two independent
streams, that one and that one.

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And the plus actually adds them both
together to form a master stream.

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So, that basically joins
the two words together.

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So I've actually got to run this now.

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Down the bottom of your
file that says hello world.

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And that's because it's actually joined
those two because we've used that plus to

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say add those two strings together.

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I'm just gonna move this run
window to the right hand corner,

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to the right hand side of the screen.

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Okay, so let's put in hello world.

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Hello plus world example that I showed you
above isn't really very impressive, but

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what we can also do is store
the strings in variables and

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it makes more sense to do that.

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So we can do something like this,
we can type greeting.

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Equals hello.

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Name equals Bruce.

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Print.

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Greeting plus name, and so, Enter.

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And the other thing is we can also
put a space between hello and Bruce,

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we could type print.

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greeting +, one space in there, + 9.

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I'm going to introduce
you now also to a comet.

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Now a comet is where you've got
something you want to add to

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sort of remind yourself perhaps, or

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give you some information about a
particular bit of code that you've added.

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If you put a hash, and type in something
like, some instructions for yourself.

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It then enables you to type that in there.

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Anything after the hash, that entire
line is ignored by the computer.

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So it's there entirely for

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your benefit to help you to help you to
understand a particular program better.

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It's always a good idea when you are
programming to put a comments in there and

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that's what this is.

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This is called a comment.

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Put as much information as you can in
there to remind yourself of why I've done

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something in a particular way,
to help you understand.

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And you'll find that when your reading
other people's program source code

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that actually happens as well,
that they comment it.

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You can read their comments and
actually understand it a bit better.

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Just to confirm, we're gonna run this.

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And you can see it's got
HelloBruce the first time.

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That's because we didn't have
a space on that line there.

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We had hello and Bruce without a space.

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And in the second line, we actually added
a space between the words hello and

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Bruce and
it actually correctly showed the space.

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All right, I'm gonna end this video here
now, because it's getting a little long.

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But when I come back we're gonna continue
on with our introduction to Python.

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And we're gonna actually have a look
at the input function which allows you

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read an unknown from a keyboard.

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So, I'll see you in that next video.