Python for Absolute Beginners Transcripts
Chapter: Writing your first lines of code
Lecture: Demo: Happy birthday to me
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Let's write a little bit of code
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play with some variables and even do a little calculation
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here in our Python REPL.
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Remember we get started by typing python3
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on Mac OS and Linux, sometimes on Windows
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we'll figure that out when we get there.
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We can get started by declaring a variable
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like we can say x = 7, y = 11.
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And then you can do just standard math.
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So the math operations, they're very much like, well
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what you will done in math class
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so x + y, we get 18, there's a prize there, right?
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And if we want to work with that value of it being added up
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we need to have another variable
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like let's say z = x + y.
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And then we can ask, what is the value of whoops
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that wasn't it, x + y.
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And then we can say, what is the value z?
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Again, it's 18.
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But then you could do things like add one more to z.
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Now what is z? z is 19.
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But then there is this little shortcut
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we can do a += to say
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take the value and increment by one.
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It's like z = z + 1, you'll see that all the time.
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So this is interesting.
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We can do basic things with these variables here
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we have x, y, we have now z, we can add them together
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we can even say z / y
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and get some sort of floating point number
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that comes out of it like that.
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Let's do something a little bit simpler and more fun maybe.
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What we're going to do is we're going to clear the screen
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and on Mac OS, you hit command K, and clear that.
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The other operating systems don't have that feature
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wish they did.
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So what we're going to do is we're going to a creative name.
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And I'll say my name is Michael.
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Now we want this to be text.
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And in programming language, in programming terms
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text always has to go into these quotes.
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We have double quotes, you can use single quotes
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or double quotes, it doesn't make any difference in Python.
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Some languages it does, Python, it doesn't matter.
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You can just use whichever you like.
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Often I actually use single quotes
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but sometimes double as well.
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So we're going to create this variable
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and ask what it is.
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Notice Python prefer single quotes
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when it refers back to us.
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It says, here's a piece of text.
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Now this type of data that we're working with
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when we have text is called a string.
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That's different than say numbers.
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So if we had like name, or we tried to add a number to it
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it'll say, oh, no, no, no
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you cannot put strings and numbers together.
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It's really important that you have a basic sense
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of the type of data you're working with
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because certain operations are allowed to be done on data
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like again, with x / y, or z / y
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you kind of can divide name by a number.
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We have a variable called name.
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And we have a piece of data, Michael, which is text
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and that's a string or str in programming syntax.
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Now, let's do something interesting with it.
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Let's say my age, I'm going to be 42, right?
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Let's put these pieces together.
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We already saw that if we try to say name + age
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it gives us an error, that's okay.
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We're going to make string, a piece of text
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out of those two pieces of data, those two variables
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though what we can do is we can create
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what's called an f-string.
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So I'll say that there's going to be a message
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and normally an f-string is like this or like this.
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But if you want to put other data into it
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like name and age, input just a little f at the beginning.
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These are format strings
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strings that take data as part of what they do.
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So we could say, Hi there, and we want to put the name
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we just put the name inside these curly braces.
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So we say name, you are, age years old. Like that.
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Though if we say what is the message?
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Hi there, Michael, you are 42 years old.
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Cool, right? So what we have is we have our string data
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which we stored into name, we have our integer data.
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That's what type? This is right?
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Notice this int here, integer age 42.
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And then we created a more interesting string using format
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a format, we said Hi there, whatever the value of name is
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you are, whatever the value of age is, years old.
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So that's cool.
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Let's go ahead and suppose I had a birthday, my age
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I could say equals age plus one, or again
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we could do that shortcut plus equals one.
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And now, if we go and do our format again
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we just hit up arrow to go back and run it.
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But if we recreate this message, we can ask what it is now.
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Hi there Michael, you are 43 years old.
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Cool, okay.
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So we can actually ask what type of data we're working with.
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It's very rare in Python that you would do this.
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But as we're kind of exploring this idea
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you can use this operator called type
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so I could say what type is message
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what type is name, what type is age.
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So you can see that it's a string, string and an integer.
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It's not important that you know the exact types
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or often that you even say them
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some programming languages
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I'd have to declare this variable as a string
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before I get assigned string values to it.
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I'd have to declare the age as an integer
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before I could assign integer values to it.
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Python is way more loose than that
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it just lets you write values and work with them.
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But as you can see, as we try to do these operations
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it does care about them.
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And so having a little bit of a sense
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that there are these different types of data
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that store different types of information
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numbers as integers and string as text.
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There's also different types of numbers
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like floating point numbers like 1.2.
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Integers just represent home numbers and so on.
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But having this little sense of a data type
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just is there in the background that you're working with
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tells you what you can do with the data
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the way you can combine it and so on.
