Python for Absolute Beginners Transcripts
Chapter: Using external Python packages
Lecture: Demo: Creating a virtual env
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The first thing that we have to do
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to get started with these external packages is
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to set up a place where can install them and manage them.
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Now, this is really easy, but it's not entirely obvious.
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So, let me just tell you a little bit of background
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and give you an example about why we're doing this
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before we go down this path, when you're working
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with these external libraries, they have versions.
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And these versions change over time
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ideally as they go forward in time
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they're always able to run older code that was written
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on them, but this is not always the case.
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Sometimes, a version one of the library won't run stuff
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that was written against version .5.
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If you're working on two projects on your computer
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and let's say they both use the Flask web framework
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one has to you 1.1, another has to use 0.2
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and they're not compatible, how are you going
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to install the same library with two versions?
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You can't and it turns out that you also want
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to maybe know what are all the packages I'm using
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for this project by itself, not that I've happened
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to install for other projects, as well.
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So, because of that, Python has this thing called
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Virtual Environments, these are like little isolated copies
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of Python that let you install
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and manage it separately, so it's isolated.
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Now, the way we do this is pretty easy
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but let me put you at a quick article here
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this one at snarky.ca, this is Brett Cannon
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he's one of the core developers
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on Python and he talks about a
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Quick-and-Dirty Guide on How to Install Packages for Python
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talks about these virtual environments
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gives you some examples, so you might want to check that
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out for more reading, but let's just get started.
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I want to go to this folder here.
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This is our folder 10 for our Get Help Repository.
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I got this cool little plug-in or extension
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for our finder here called Go to Shell
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I think Windows has something like Go to Command Prompt
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or Power Tool or something like that
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I'm not sure what the best way
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on Windows is to do the same thing
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but you can always just CD over there.
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So, in here where our files and what not are
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we're going to run a command that will tell Python
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to make a little copy of itself.
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And it has this library called pip
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pip is how we install and manage these external systems
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and external libraries, but one of the things you can do
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is say, pip list, and here's a whole bunch of stuff
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that somehow got installed into my computer
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but I don't want those, I want it separate
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little tiny isolated one, so what I'm going to do
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is I'm going to say, python3 -m for run a module.
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venv the name of the module is virtual environment.
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venv then I'm going to give it a folder which I also
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by convention call venv. That's a little bit annoying
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that it kind of looks like that or unclear I don't know but
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it's fine you'll get used to it.
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So that's going to take a moment.
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And then if you take a look here
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there's a folder called venv and if we look in there
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there's a bin, and if we look in bin, you can see
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there's hey a little Python and then there's a little pip
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and so on. But what we care about is activate
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activate right there. So on Windows this is scripts not bin
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but otherwise it's basically the same.
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To make this active what we have to do in the Shell
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is we have to say dot space or you can say source space.
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One of those, either those are fine on Mac OS and on Linux
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on windows just don't put anything.
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I'll show you the Windows command in a second.
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We say venv/bin/activate. Now see my prompt here?
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It gets this in here now if I say pip list
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it's just those two. And it's kind of annoying
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but it always installs a version that it came with
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not the lastest version.
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So you usually want to run that little command
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now if we ask for pip list then we get that. Cool.
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So on Mac OS and Linux you say this and on Windows
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you say, you get the dot, you just say venv\script\activate
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which is activate dot that.
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And that will have the same effect.
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So now we've got this little isolated version of Python
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and we can install things in here. So right now as you saw
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we have our pip list. Just as these two.
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But we're going to use the colorama library.
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We can install that PyCharm or we can install that here.
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I'll do one library here and one library in PyCharm.
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So we can say pip install colorama.
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The library that lets us add color output.
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And now if we ask for pip list.
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You can see colorama is installed as well. Okay great.
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So now we're ready to get going with this environment
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and this program so I'm going to put that
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actually it's already ready over here
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let's load this up in PyCharm.
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Now one thing that can happen over here is the project
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interpreter it might not have detected this.
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Sometimes it does sometimes it doesn't.
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So you can see whether or not
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you can choose an exisiting one
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and browse over to it and so on.
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But you want to go and click add if it doesn't already
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find it because it selected it, it wasn't in the list.
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So here you can see colorama, pip, and, so on.
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You can even add stuff through PyCharm here, I can add
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request with a common library, or I can click the install
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or if there's an update I can hit like
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here this one has an update, okay hit that little up
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that and we give it a second. Move over to this side.
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Didn't mean to click that up sorry.
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Right here it's doing something now it was updated. Cool.
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So that's a nice visual way to manage that stuff as well.
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One thing you want to do with these virtual environments
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is make sure they're ignored.
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See how they're like grayed out? Whatever.
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Okay great. Alright so we're now ready to use this library
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we can come down here and we can say import colorama
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and because we pip installed it into
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our virtual environment, the virtual environment
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you can see down here, is active right there.
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That means that we can use this library
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and PyCharm won't give us an error
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it knows about it and we can start programming against it.
