Python for Absolute Beginners Transcripts
Chapter: Writing your first lines of code
Lecture: Using a built-in library

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0:00 Now before we ramp up this chapter
0:02 let's write one more program
0:04 in our Python REPL, and again
0:06 it doesn't really make sense to call it a program
0:08 but it kind of is.
0:10 We're going to cover two new concepts
0:13 in this video here.
0:14 We're going to talk about using libraries.
0:17 Now, Python has an incredible amount
0:20 of features built into it.
0:23 It has ways to get stuff off the internet
0:25 to work with the calendars
0:27 and the clock, and date/times
0:28 and work with collections
0:30 and do all sorts of interesting things.
0:32 You could even create a little web server
0:34 out of the stuff that comes bundled in Python
0:37 but it's not immediately available for you.
0:39 You have to ask for it as part of your program.
0:41 So, let's see how that goes.
0:42 We're going to start up our Python REPL again.
0:45 Remember, macOS and Linux, you type python3
0:48 Windows 10, you might type python3
0:50 if you got it from the Window's store
0:51 otherwise you type python.
0:53 So, here we are and what we want to do is
0:55 we want to work with this library called sys.
0:57 Now sys comes with Python
0:59 you don't have to do anything to get it.
1:00 Once you have Python, you have sys.
1:02 But if I type that, it says
1:03 Whoa, we don't know what sys is.
1:06 So, let's fix that.
1:08 The way that you work with these libraries is
1:10 you use the import keyword.
1:12 So we're going to say import
1:14 we want to work with import sys.
1:17 If that doesn't crash, if that works
1:19 then that means that sys was loaded.
1:20 You could ask for import
1:22 some random set of characters
1:24 and it would crash because
1:25 there is no library called that, right?
1:27 But there is a library called sys
1:29 so that worked and we loaded it.
1:30 Now if we ask what sys is
1:31 It's a built-in module
1:34 and sys has a bunch of cool stuff.
1:35 So we could say sys.versioninfo
1:39 and here you can see it gives some kind of
1:41 complicated response that seems to indicate
1:44 there's a major version is 3, minor version is 7
1:47 micro version is 6, releaselevel is final
1:50 and serial equals 0.
1:51 That should correspond pretty closely to 3.7.6
1:55 which is the version of Python that we have.
1:56 But now that we have this library loaded
1:58 we can actually use it, all right?
2:01 This isn't going to be super interesting
2:02 but we could come up with
2:03 some kind of string or message
2:05 where we want to print out a message
2:07 that Python says, Hello
2:09 instead of just, Hello, and welcome to Python
2:11 it'll be, Hello, and welcome to Python version 3.7.6
2:14 on my machine, but maybe it would say 3.8.1 on yours.
2:17 It will say whatever the version of that, is.
2:19 So, remember we want a string
2:20 which we go like this, there's our string
2:23 and we want to format it, so we put the f.
2:25 Let's say, Hello from Python
2:28 you can just say it like that
2:29 and, Hey, hello from Python
2:31 but we want is the version info in here.
2:34 Now remember, we need to say
2:36 sys.versioninfo.major
2:43 and then we say. And this is not going to be pretty
2:46 we're going to do a better version here.
2:48 sys.versioninfo.minor
2:52 let's just say from Python 3.7
2:54 okay 'cause, it's gettin' long.
2:55 Hello from Python 3.7, well
2:58 this is a lot to type and you might
2:59 want to work with those numbers elsewhere and so on.
3:01 So, we could say ma equals the major version
3:05 so sys.versioninfo
3:09 like that.
3:10 We could check what ma is, it's 3
3:11 and then mi for minor.
3:17 Here we go, and that will let us
3:19 I'm just using up arrow to get the history back.
3:22 That'll let us write something way nicer here.
3:23 So we can say, ma.mi
3:27 like this.
3:28 Same thing, but this, I think
3:30 is a little bit more clear.
3:31 You don't want to try to cram too much
3:33 to have too much going on in there.
3:35 So, I kind of like to do it this way
3:36 but you can do whatever works for you.
3:38 Here we go, Hello from Python 3.7.
3:42 If you'd written on your machine
3:43 and you had a different version
3:44 let's say you had 3.8.
3:46 This exact same code would say
3:48 Hello from Python 3.8.
3:50 Pretty cool, huh?
3:51 Now remember, the reason that that works
3:53 is because we're using this library.
3:55 It happens to be
3:56 this library is built into Python and comes with it.
3:58 You can get others and add it to Python
4:00 that's something awesome and we're going to do that
4:02 and really take advantage of some cool stuff
4:04 but for the moment, we're just sticking with
4:07 the so called, Built-ins.
4:08 Let's see why they're called built-ins.