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
Now that we’ve got a virtual environment set up, we’ll install some libraries. We’ll see how these are only installed within our virtual environment and not outside of it.
Commands
To install a package
-
pip install [name]- replace[name]with what you want to install
To install a specific version of a package
-
pip install [name]==[version]- replace[version]with the version you want to install
To upgrade a package to the latest version
pip install --upgrade [name]
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
You may have noticed in your Python
adventures that the terms module, package
0:00
and library are all used to describe
third-party code that we can install.
0:05
A module is an executable.py file that
contains functions and variables.
0:11
A package is a group of modules, and
a library is a group of packages.
0:17
Just know that they all refer to a chunk
of code from a third party that we
0:23
can install and use.
0:28
Now that we have a virtual
environment set up,
0:30
we can install the necessary
third-party libraries.
0:34
For this project,
we'll install Flask and SQLAlchemy,
0:38
the two libraries our
app.py is trying to import.
0:42
These installed libraries are referred
to as the dependencies for
0:47
a project because a project
depends on them to run.
0:51
In your terminal, let's first
reactivate the virtual environment.
0:56
A neat trick to use a command
you've recently used is
1:01
to press the Up arrow to move
through your command history.
1:04
Here we just have to press it twice to get
to our activation command, press Enter.
1:09
Check that our command line
is now showing the myapp-env
1:18
prefix to make sure we're
inside the virtual environment,
1:23
then type pip install flask.
1:28
Let's break it down. pip is the built-in
package installer for Python.
1:35
The pip keyword tells Python that we're
about to do something with the packages
1:42
for this project.
1:46
Install is a pip command, which tells pip
that we want to install something and
1:49
flask is the name of
the package we want to install.
1:55
This part will be different depending on
what you want to install, for example,
2:00
SQLAlchemy or requests.
2:05
You may see a notice, like this one,
2:08
about a new release of pip being
available and it's extremely common.
2:11
Pip is a default package that gets
installed when Python was installed.
2:17
When a virtual environment is created,
this version of pip was used.
2:22
Since pip updates more
frequently than Python,
2:28
naturally our version of pip
will likely need updating.
2:31
You only need to update pip once for
your global installation of Python, but
2:36
you'll likely need to do this every
time a new environment is created.
2:41
Luckily, it's super easy, and
pip even provides the exact command for
2:47
us, so let's use it right away.
2:52
pip install –upgrade pip, this is also
2:54
the command format that
we use when we want
3:03
to update any of our other libraries.
3:04
Sometimes we may want to install
a specific version of a library, and
3:09
pip makes it super easy to do that.
3:14
We simply have to specify
the version number after the library
3:17
name joined by two equal signs.
3:22
Let's install version 2.0.8
3:24
of SQLAlchemy by using the command pip
3:28
pip install sqlalchemy==2.0.8, press Enter.
3:31
Now if you want to update
this to the latest version,
3:44
we'll just use that upgrade
command that we learned earlier,
3:48
pip install --upgrade sqlalchemy,
and Enter.
3:52
Now, let's try running our
project using python3 app.py.
4:02
And you'll see a success message,
nice work.
4:10
You now have a virtual environment
that has some libraries installed, and
4:14
we can start using these
libraries within our project.
4:18
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up