3.2.7. Python virtual environments#
A virtual environment is a self-contained directory tree containing Python and some additional packages.
Advantages#
These are some advantages of using virtual environments.
No administrator privileges#
You do not need administrator privileges to create a virtual environment or install packages in an environment.
Multiple environments#
Multiple virtual environments can be created with each containing their own sets of packages.
These are isolated and packages in an environment can be installed, updated or removed without affecting other environments.
Creating a virtual environment#
First, using The quick and easy method, search and
install the python3-venv package. This includes the
venv module necessary for creating virtual environments.
You can create a virtual environment in any directory where you have write privileges, for example, your home directory.
To demonstrate, I will create a virtual environment called
py3env in my home directory.
python3 -m venv py3env
If successful, you will find a directory named py3env
in the current directory. No messages will be displayed.
Note
python3 is the command to run the Python 3
interpreter. Its complete path is /usr/bin/python3.
venv is the Python module to create virtual
environments.
The -m option runs the venv module as a script.
Before you can use a virtual environment, you will need to activate it.
Activating a virtual environment#
You will need to activate a virtual environment before you
can start using it. To do so, use the source command
with the path to the virtual environment’s activate
script.
For example, to activate py3env created in the
previous step, use:
source py3env/bin/activate
Your shell prompt will now change to indicate that
the virtual environment is now active.
Note the (py3env) label at the beginning of the
prompt:
(py3env) user@cookbook:~$
You can now start using this virtual environment.
Note
Before you start installing packages…
It is a good idea to install (or upgrade) Python build tools — pip, setuptools, and wheel in a new virtual environment.
These build tools are necessary for building and installing packages from PyPI and other sources.
Installing them will ensure that additional packages will build and install without errors.
Installing Python build tools#
Use pip3 install to install or upgrade the
required packages:
pip3 install -U pip setuptools wheel
The -U option of pip3 install, will upgrade
listed packages, if newer versions are available.
Output:
Collecting pip
Downloading pip-21.0.1-py3-none-any.whl (1.5 MB)
...
Installing collected packages: pip, setuptools, wheel
...
Successfully installed pip-21.0.1 setuptools-54.2.0 wheel-0.36.2
Deactivating a virtual environment#
To exit a virtual environment, use the command:
deactivate
Your shell prompt will change to its original appearance:
user@cookbook:~$