Python for Absolute Beginners Transcripts
Chapter: Writing your first lines of code
Lecture: Concept: Variables and types

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0:00 Let's review this idea of variables
0:02 data values, and types.
0:04 We saw that we can create variables
0:06 just by saying their name, and then giving them a value.
0:09 Though, in our Python REPL, Read, Eval, Print, Loop
0:12 we were able to type x = 42.
0:15 Notice this green dip with a hash
0:17 in Python you can make comments
0:19 that are meant for people that have no effect
0:21 on how code runs.
0:22 So we're going to say hash if we were to run Typhon X
0:26 but what we'd get back is this class inch.
0:29 Remember we said there's a way in Python to ask
0:31 What type of data are we working with?
0:34 And here when you work with whole numbers in Python
0:36 that's an integer.
0:37 We came up with another variable, 19, also an integer
0:41 then we saw we can use them in expressions
0:43 like what is x + 7 * y?
0:47 Then if we don't assign it to a value
0:48 that just kicks out whatever the response
0:50 or the evaluation, the value of it is, so 175.
0:54 We can also create text base data
0:58 and these are strings.
0:59 They go in single quotes, or double quotes.
1:01 Like we have here, so we said name = 'Michael'.
1:04 Now if we asked the type again
1:06 this one has changed from int to str.
1:08 And you can combine strings and numbers
1:12 by adding them together
1:13 but if you try to mix these types
1:15 it doesn't really like it so much.
1:16 Here we saw that there was an error
1:18 if we said name + x.
1:20 We got an exception.
1:21 The program sort of crashed
1:23 and if it was a real program that we were running
1:24 it wouldn't continue, it would just stop and say
1:26 Something's broken, we're done.
1:28 But in the REPL it just prints out the error
1:30 and carries on.
1:31 If we didn't want to combine numbers and strings
1:34 we can use a format string.
1:36 We know we have a format string
1:37 because it has that little f at the beginning.
1:38 So here we say, Hi, pearly name.
1:42 And that just takes the value, currently Michael.
1:44 Looks like you did math, and then we want to restate
1:47 the equation and then the value.
1:48 So x, {x + 7 * y}
1:52 is going to be whatever that value is.
1:54 Now, I could've assigned that response
1:57 or that evaluation to a variable.
2:00 We could've said something like
2:01 z = x + 7 * Y
2:04 and that's probably the best thing to do actually.
2:06 But I wanted to make the point
2:08 that it's not just variables
2:10 that can go into these format strings
2:12 inside those curly braces.
2:14 More general Python expressions can go in there.
2:16 So, if you wanted to compute something
2:18 or you wanted to call a function
2:20 get some behavior out of a piece of data
2:22 we'll see how to do that later.
2:23 You can do that there.
2:25 So, these are very very flexible.
2:26 And we run this code, we get Hey Michael
2:28 looks like you did math, 42 + 7 * 19 is 175.
2:34 Aright, so here we've created a bunch of variables
2:35 we've set their data and we've set their data values
2:39 which implies a data type.
2:41 We saw that we don't say the type in Python
2:43 but that it is important to know about it.
2:45 Like for example, name plus X, we should know
2:48 that we can't do those things.
2:49 We need to do the thing at the bottom.
2:51 Create that cool little string that we got in the end.