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