Python venv: Virtual Environments

Python virtual environments, also known as venv, are a way to isolate different Python environments. This is especially useful during development, as it allows you to install packages with pip separately for each project. This setup eliminates the risk of version conflicts, which can arise when one project requires a specific version of a package, while another project needs a newer version of the same package. Previously, this issue might have been addressed by creating a separate virtual machine or container for each project, a time-consuming and resource-intensive approach. Here’s how to set up venv quickly and easily.

Creating a venv Environment

A venv environment is essentially a folder that you point Python to as the location for installing packages. You can create this folder anywhere you want, such as within the project directory you’re working on. However, remember to add this folder to .gitignore if you’re using version control. Personally, I prefer to keep all environments in a single directory.

The following example applies to Python 3.4 and higher. Prepare a folder for the development environment of your project:

py@e73a39cc4acc:~$ mkdir -p .venvs/pocket-tools

py@e73a39cc4acc:~$ ls -al .venvs/
total 16
drwxrwxr-x 4 py py 4096 Nov  8 18:58 .
drwxr-x--- 4 py py 4096 Nov  8 18:58 ..
drwxrwxr-x 2 py py 4096 Nov  8 18:58 pocket-tools

Now create the environment itself:

py@e73a39cc4acc:~$ python3 -m venv .venvs/pocket-tools

Activating the venv Environment

Use the source command to activate the environment by specifying the /bin/activate file inside the environment directory:

py@e73a39cc4acc:~$ source .venvs/pocket-tools/bin/activate
(pocket-tools) py@e73a39cc4acc:~$

Note that the name of the active environment appears before the username in the bash prompt. Now let’s install some packages for Python and compare them with those in another environment. Clone the pocket-tools project and install the dependencies defined in the requirements.txt file:

(pocket-tools) py@e73a39cc4acc:~$ git clone https://github.com/skaczmarek-dev/pocket-tools
(pocket-tools) py@e73a39cc4acc:~$ pip install -r pocket-tools/requirements.txt

List all the packages installed by PIP:

(pocket-tools) py@e73a39cc4acc:~$ pip freeze
certifi==2024.8.30
charset-normalizer==3.4.0
idna==3.10
requests==2.32.3
urllib3==2.2.3

Now exit the active venv environment and list the packages installed by PIP in the default Python environment:

(pocket-tools) py@e73a39cc4acc:~$ deactivate
py@e73a39cc4acc:~$ pip freeze
setuptools==68.1.2
wheel==0.42.0

As you can see, the default Python environment contains different packages than the pocket-tools environment, and the deactivate command is used to exit the active environment.