Python 3, an illustrated tour Transcripts
Chapter: Virtual Environments
Lecture: Walk-through: Virtual Environments and Pip (Unix)

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0:00 In this video, we're going to look at the venv test assignment
0:03 and we're going to do on Unix system so that'll work on Linux or Mac systems.
0:08 I've got the files downloaded from the labs here.
0:12 Let's look at the venv test lab
0:15 and you can see there's the assignment in that comment
0:17 under the test venv function that says
0:20 use pipenv to create a virtual environment and install pytest
0:22 activate your virtual environment and run pytest on this file
0:26 by invoking python venv test.py
0:30 You'll note that this will run pytest because at the bottom there
0:34 we've got the check for if the __name__ attribute is the string __main__
0:37 import pytest and invoke pytest.main on the file.
0:41 So let's do that, I'm going to create what's called a user install.
0:46 If you don't have access right to your system or install into your system python,
0:51 you might need to do a user install, it has a few more steps, so this is how we do it.
0:55 We say Python 3 -m pip install --user and we're going to install pipenv.
1:03 Okay, it looks like that installed.
1:07 Now what I need to do is be able to access the pipenv command-line utility
1:12 and because I installed that in a user install, python installed in a certain place,
1:17 I'll show you where it came. Python -m I'm going to invoke the site module
1:21 and say user-base, that says that it put it in my home directory
1:28 in library Python 3.
1:30 So in there, I should see a bin pipenv executable.
1:35 Let's see if that exists in the bin directory and there is a pipenv.
1:41 So now what I want to do is I want to make sure that this bin directory is in my path.
1:45 So I'm going to update my .bash profile.
1:48 I'll just show you how I update it.
1:54 It looks like that, and once you've updated that
1:57 you can source that file and you should be able to say which pipenv
2:05 and it should tell you that it's using the user-installed pipenv.
2:09 Great, at this point, I'm ready to use pipenv
2:12 and note that I'm in my directory, where I want to create the virtual environment,
2:16 I want to do it in the lab directory.
2:18 If you don't create it from inside the directory you want to
2:21 you might have problems activating it automatically using the pipenv tool.
2:26 So make sure you're in the right directory here.
2:28 All you have to say is pipenv install pytest.
2:33 So it says it's creating a virtual environment for the project and it's installing pytest.
2:41 You can see up at the very top it says
2:44 where the directory is in the virtual environment,
2:46 it's in my home directory in the .local folder.
2:49 So if I just list the contents of the home directory,
2:52 I'm not going to see that because it starts with a period
2:55 so I have to do an ls-al to actually get the local directory there.
3:05 And you can see up at the top here,
3:09 there's a .local directory there.
3:14 Okay, so inside of that local directory,
3:20 there's a shared directory and then there's virtual environments inside of there
3:23 and it created this guy right here, talkpy3 -labs
3:26 and if you look, there's a bin directory and there's an activate guy in there.
3:31 We're not going to run this the traditional way,
3:33 we're going to use the pipenv tooling to activate this.
3:35 So how we activate with pipenv is we say pipenv shell.
3:39 And you'll see that it says it's spawning an environment
3:43 and it says use exit to leave.
3:45 So in this case, we don't use deactivate
3:47 which is the traditional virtual environment command to leave the shell
3:50 we're going to use exit and also note that it updated our prompt here
3:54 and it said that we're using this environment here.
3:57 You'll also note that when we ran pipenv,
4:00 it created these two files here pipfile and pipfile.lock
4:03 Let's just look at pipfile and you can see that it says that it has installed pytest,
4:10 we can look at the lock file.
4:14 The lock file has hashes for all the different libraries that we've installed.
4:18 So if we want to get specific libraries reinstalled,
4:21 it's going to check those hashes to make sure that they're the same versions,
4:24 nice little feature here.
4:26 Okay at this point, I should have pytest, let's see if pytest is found
4:30 and it's found in my virtual environment, cool.
4:34 Let's say which python to make sure that I'm using
4:38 the python from my virtual environment,
4:40 which Python, and in this case, I don't need to say Python 3 anymore
4:43 because when we created the virtual environment
4:47 it made an executable called python that is Python 3 there.
4:49 I can also say Python 3, but those should be the same,
4:52 just to show you if I type python now it says Python 3.6.
4:58 Okay, and finally, let's run venv test
5:01 and it says it ran one passed in 0.1 seconds.
5:06 So that's how you create a virtual environment and install pytest using pipenv.
5:12 I'm also going to exit from this.
5:14 I'm going to say exit and you'll see that now I am out of my virtual environment.
5:19 So this video showed you how to use pipenv to create a virtual environment
5:24 and to install files, how to activate the virtual environment and how to exit from it.