Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Preview
Start a free Courses trial
to watch this video
`virtualenv` is a tool that allows us to segregate our Python projects from each other. In this video, I'll show you how to use Python 3.5's built-in `venv` module to create virtual environments.
The command to create a new virtualenv is python -m venv <virtualenv name>.
You can refer to the docs for more information about the venv module.
Inside of your virtualenv, you'l likely use the python and pip commands instead of python3 and pip3.
So virtual env is a tool that lets us have
separate worlds of python libraries for
0:01
separate projects.
0:06
So for instance,
0:07
right now I am in a thing called new
project, super duper creative name.
0:08
And so I want to make a new virtual env so
that I can install my stuff here for
0:13
new project, so
it doesn't conflict with old project.
0:18
Normally when you install something
with Pip, it gets installed to
0:22
a global repository of libraries,
usually called site packages.
0:25
But what if you do one
project with Django 1.8, and
0:30
your next project is with Django 1.9?
0:33
You'd have to make sure that your
1.8 project still works with
0:35
1.9 once you upgrade.
0:39
Or you'd have to decide
not to use Django 1.9.
0:41
You'd have to decide not to upgrade and
just build everything with Django
0:45
1.8 from now on forever and
ever because you never upgrade.
0:49
Or for the best of all the worlds,
you use virtual env for
0:53
each of your projects and you just
install whatever that project needs.
0:57
Now, back in the days of Python 2, and
even the first couple of versions of
1:02
Python 3, you had to install
a separate tool to use virtual env.
1:06
So you'd see instructions
like pip3 install virtualenv.
1:10
But as of Python 3.3,
1:15
virtual env has actually been merged
into the Python standard library.
1:17
So now you can use it without
having to install anything.
1:22
This is awesome.
1:25
So how do we create a virtual env?
1:27
So I've gone ahead and I've made a place
to do my treehouse Python learning.
1:31
I'm just inside of documents and
I've what is it, where am I?
1:35
Whatever.
1:41
Anyway, I'm inside of [LAUGH],
you can see I went into documents and
1:42
I just made a folder called, new project.
1:45
You know,
maybe you'd wanna do like treehouse, and
1:48
then let's move idle and
new project inside treehouse.
1:54
Alright so, maybe you'd want to do that.
2:02
And I'm gonna pretend that I'm about
to start on the flash basics course.
2:04
Maybe you're already done with that
course, maybe you haven't started it yet
2:09
or you know, or maybe you did it or
2:12
you're going to do it in workspaces and
that's a great idea.
2:14
Let's make a directory for our course.
2:17
You do this for each of your projects too.
2:20
Maybe you're building a library website or
2:22
something, you'd make a directory for
that.
2:25
So we're going to make a directory for
flask basics and we're gonna go in there.
2:27
And now, let's clear my screen.
2:32
Now I need to make the virtual env.
2:35
I can call the virtual
env anything I want, but
2:36
generally you want to avoid the names of
libraries that you're likely to install,
2:39
or the virtual env module itself,
which is actually named VEMV.
2:43
So this is for flash basics,
I'm going to use the initials fb.
2:47
So python three dash mvemv.
2:52
And now it expects a name.
2:55
We're gonna put in fb.
2:57
So that dash m flag,
this thing right here,
2:59
that actually tells Python
to use a particular module.
3:04
Modules have or can have a bit of special
code written in them that when they're
3:08
used this way, which the venv module
has of course, it knows what to do.
3:12
It has like a special invocation.
3:18
So what this does is it expects
the name of a virtual env to create,
3:21
which it got and
then it creates a virtual env using that.
3:26
So if we look,
we'll see here that we have fb, and
3:29
if we do ls of fb, then we see
the virtual env bits and pieces.
3:33
Now we don't want to make
our code inside of fb.
3:38
This is where libraries get installed too.
3:42
We don't want to write
our own code in there.
3:44
The reason is because at any point,
I should be able to just do that.
3:46
And that, and other than installing
some packages, I'm right back to normal.
3:50
Nothing's new.
3:57
OK, now, before we can use the virtual
env, we have to activate it.
3:58
So we'll do source fb,
then activate, and that's it.
4:02
It's activated.
4:09
I know it's activated because I have
this little parentheses fb parentheses
4:10
over here, and that says hey you're
working in the fb virtual env.
4:15
Which, for
4:19
example if I do which Python you see
that it's the Python inside fb bin.
4:20
Right?
4:25
It's not one way on the outside.
4:25
And if I do Python version, it's 3.5.
4:27
So even though it was Python
3 outside of the virtual env,
4:31
inside the virtual env it's just Python.
4:35
And now if I want to install things
I can just use pip to install them.
4:38
So we'll do pip install Flask, which is
the thing I'm probably gonna need for
4:42
Flask basics.
4:44
And it downloads and installs this stuff.
4:46
And I just go on making
code like I normally would,
4:49
just like the course tells me to.
4:52
You need to sign up for Treehouse in order to download course files.
Sign up