Python venv
last modified January 29, 2024
Python venv tutorial shows how to user virtual environments in Python using the venv module.
Virtual environment
Complex applications rely on a number of different dependencies. Various
applications may depend on a library, or different versions of the same library.
Since Python cannot differentiate between versions in its
site-packages directory, virtual environments were created as
a solution.
IDEs including Visual Code and PyCharm have extensive support for virtual environments.
A virtual environment is a self-contained directory tree that contains a Python installation for a particular version of Python and a number of additional packages.
Common installation tools such as setuptools and pip
work as expected with virtual environments. When a virtual environment is
active, they install Python packages into the virtual environment without
needing to be told to do so explicitly.
Python venv
The venv module enables to create lightweight virtual environments
with their own site directories. Each virtual environment has its own Python
binary (which matches the version of the binary that was used to create this
environment) and can have its own independent set of installed Python packages
in its site directories. (The site directories are directories where we install
third-party modules.)
Python create virtual environment
Next we show how to create a virtual environment.
$ python --version Python 3.8.5 $ python -m venv myenv . myenv/bin/activate
These commands create and activate a new virtual environment on Linux.
> py --version Python 3.8.1 > py -m venv myenv > myenv\Scripts\activate
These commands create and activate a new virtual environment on Windows.
$ ls myenv/ bin include lib lib64 pyvenv.cfg share
The bin directory contains tools that interact with the
virtual environment. The include directory contains C headers
that compile the Python packages. The lib directory contains
a copy of the Python version. It also includes the site-packages
subdirectory.
The pyvenv.cfg is a configuration file which stores information
about the virtual environment such as the original Python that the environment
was cloned from (and which will provide the standard library) and the version of
the interpreter.
$ cat myenv/pyvenv.cfg home = /usr/bin include-system-site-packages = false version = 3.8.5
This is a sample output of the pyvenv.cfg file.
Python activate virtual environment
Before we can use a virtual environment, we need to activate it first.
$ python -m venv myenv
We create a new virtual environment called myenv.
$ . myenv/bin/activate (myenv) $
We activate the virtual environment. We can see the name of the environment in the prompt.
(myenv) $ echo $PATH /janbodnar/Documents/prog/python/venv/myenv/bin:/janbodnar/.cargo/bin/:/janbodnar/ Documents/prog/go-workspace/bin/:/janbodnar/.config/composer/vendor/bin/: ...
The PATH environment is updated; the virtual environment's
bin directory is at the beginnig.
(myenv) $ which pip python /root/Documents/prog/python/venv/myenv/bin/pip /root/Documents/prog/python/venv/myenv/bin/python
The which command returns the path to the virtual environment's
pip and python.
(myenv) $ deactivate $
With the deactivate command, we terminate the virtual environment
and go back to the shell.
Python venv installing packages
After activating the created virtual environment, the pip tool
installs the packages into the environment.
(myenv) $ pip list Package Version ------------- ------- pip 20.0.2 pkg-resources 0.0.0 setuptools 46.1.3
We show the available packages with the pip list command. As we can
see, at this moment we have a bare minimum of packages.
(myenv) $ pip install requests urllib3
Into our new environment, we install the requests and the
urllib3 modules.
(myenv) $ pip list Package Version ------------- --------- certifi 2020.6.20 chardet 3.0.4 idna 2.10 pip 20.0.2 pkg-resources 0.0.0 requests 2.24.0 setuptools 46.1.3 urllib3 1.25.10
We list the available packages again. In addition to the requests
and urllib3 modules, we have additional modules installed by the
two installed modules.
(myenv) $ pip freeze --local | xargs pip uninstall -y
To go to a clean state and remove all installed packages, we can execute this command.
(myenv) $ deactivate $
To jump out of the virtual environment, we use the deactivate
command.
$ pip list Package Version ---------------------------- -------------- adblockparser 0.7 AdvancedHTTPServer 2.2.0 aiocmd 0.1.2 aiodns 2.0.0 aiohttp 3.6.2 aioredis 1.3.1 aiowinreg 0.0.3 ajpy 0.0.4 alembic 1.4.2.dev0 aniso8601 8.0.0 apispec 3.3.1 apispec-webframeworks 0.5.2 APScheduler 0.0.0 asciitree 0.3.3 asn1crypto 1.4.0 ...
Outside of a virtual environment, we refer to the standard Python installation. It has naturally many more packages.
$ rm -rf myenv/
If we do not need the virtual environment anymore, we can simply remove its directory.
Source
Python venv - creation of virtual environments
In this article we have created Python virtual environments using venv.
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