Python for Absolute Beginners Transcripts
Chapter: Writing your first lines of code
Lecture: Concept: Variables and types
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Let's review this idea of variables
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data values, and types.
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We saw that we can create variables
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just by saying their name, and then giving them a value.
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Though, in our Python REPL, Read, Eval, Print, Loop
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we were able to type x = 42.
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Notice this green dip with a hash
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in Python you can make comments
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that are meant for people that have no effect
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on how code runs.
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So we're going to say hash if we were to run Typhon X
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but what we'd get back is this class inch.
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Remember we said there's a way in Python to ask
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What type of data are we working with?
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And here when you work with whole numbers in Python
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that's an integer.
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We came up with another variable, 19, also an integer
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then we saw we can use them in expressions
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like what is x + 7 * y?
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Then if we don't assign it to a value
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that just kicks out whatever the response
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or the evaluation, the value of it is, so 175.
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We can also create text base data
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and these are strings.
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They go in single quotes, or double quotes.
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Like we have here, so we said name = 'Michael'.
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Now if we asked the type again
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this one has changed from int to str.
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And you can combine strings and numbers
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by adding them together
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but if you try to mix these types
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it doesn't really like it so much.
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Here we saw that there was an error
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if we said name + x.
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We got an exception.
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The program sort of crashed
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and if it was a real program that we were running
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it wouldn't continue, it would just stop and say
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Something's broken, we're done.
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But in the REPL it just prints out the error
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and carries on.
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If we didn't want to combine numbers and strings
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we can use a format string.
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We know we have a format string
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because it has that little f at the beginning.
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So here we say, Hi, pearly name.
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And that just takes the value, currently Michael.
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Looks like you did math, and then we want to restate
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the equation and then the value.
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So x, {x + 7 * y}
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is going to be whatever that value is.
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Now, I could've assigned that response
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or that evaluation to a variable.
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We could've said something like
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z = x + 7 * Y
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and that's probably the best thing to do actually.
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But I wanted to make the point
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that it's not just variables
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that can go into these format strings
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inside those curly braces.
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More general Python expressions can go in there.
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So, if you wanted to compute something
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or you wanted to call a function
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get some behavior out of a piece of data
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we'll see how to do that later.
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You can do that there.
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So, these are very very flexible.
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And we run this code, we get Hey Michael
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looks like you did math, 42 + 7 * 19 is 175.
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Aright, so here we've created a bunch of variables
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we've set their data and we've set their data values
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which implies a data type.
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We saw that we don't say the type in Python
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but that it is important to know about it.
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Like for example, name plus X, we should know
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that we can't do those things.
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We need to do the thing at the bottom.
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Create that cool little string that we got in the end.
