Welcome back everyone, let's talk about variables now. Now you can probably guess
by the name a variable is something that is variable meaning that the name
the value of it is not always going to be constant. So by explicitly
stating strings they're not reusable as well. If I wanted to you know say let's
jump into a Python console, alright. If I wanted to create a string not using
variables,
"This is a string" I could create that. However, there's no way now for me to
reuse it to do something else so I'd have to do "This is a string" + "Hello"
and then there's no way for me to reuse that one and see you can see the problem.
Now that's a one reason why we use variables is so we can reuse the variables,
now another reason is because when you pass values into functions
it's going to take on the form of variable through the parameter list of
the function, we will get more functions later.
Now the difference between Python and some other programming languages is some
programming languages are typed, and you might say well hey aren't all programming
languages typed? Yes, you type them with your fingers on the keyboard,
however a typed language basically means that you need to define the type of
variable. So as we learned in the previous videos the different types are
integers, strings, booleans and stuff like that. So if you're setting a string
variable you would have to explicitly tell the program that it's a string but with
Python you don't need to do that. All you need to do is give your variable a name
and a value. So, let's go ahead and let's create a variable called greeting and
it's going to equal a string that's going to say "greeting = "hello world""
Now you'll notice when I hit enter it didn't print anything on the screen and
it didn't do anything noticeable and it's because setting a variable doesn't
have
have any type of response, so it just creates variable and it's there. Now we
can use it by using greeting. So I could type "print(greeting)" and it's going to
print "hello world" Now also now that I've got it in a variable we can manipulate
that variable in a number of ways. So i'm going to type
"greeting = greeting.split(" ")[0]"
So basically what we're doing here, and I can't use double quotation or
double equal sign there, we're setting greeting to a new value which is going
to be greeting which we're gonna split at the space, so we're going to split it
right here, and we're going to get the first item in there. So it's going to turn
greeting into just Hello.
So let's hit enter here. We've assigned it a new value so if we
now go ahead and "print(greeting)" you're going to see that it says Hello.
So now what we can do is now concatenate this with something else. So, we can do
that in a number of ways we can reuse the previous example where we just let's
just print it out first, we can "print(greeting + " Nick")" and it's going to
say Hello Nick.
Now if we wanted to store that in a variable we could do the same thing that
we did before, or you can continue using this variable for different people. So I
could say "print(greeting + "someone else""
and so that's how that works. Now if i did want to make the
greeting equal to concatenate a string all you have to do is redefine it as
"greeting = greeting + "Nick" Now when we print out greeting you'll see
that it says Hello Nick.
So that's a variable and the useful things that you can do with it, now you
can also assign values of other types.
So we can say number is going to equal 1 and then second number is going to equal
2. So now we've got number and second number stored in variables.
Let's do something with that. So, what we're just going to do is add these
two numbers together in a print statement. So, "print(number * secondnumber
+ secondnumber * number)" and this is going to print out 4. So
essentially what the print statement is doing is before it prints it out it's
calculating this because we've stored these as integers, and so it's going
1*2+2*1 So it's essentially saying 1*2 + 1*2 and it's coming up
with this, so. And as well you can set "check = True" So, that's how to set
variables,
it's pretty simple and we're going to be doing a lot of this so this is a concept
that you're going to have to be very familiar with, and get used to using it.
In the next video, we're going to be talking about some built-in functions,
and we've already actually talked about some of them.