Python Virtual Environments

In Python, running pip install saves dependencies globally on your operating system by default. This can cause conflicts when different projects require different versions of the same library.

The solution to this problem is creating virtual environments. A virtual environment (venv) is a self-contained directory that acts as a secure bubble holding its own isolated Python binary and local dependencies.

1. Configuration (for Linux and macOS)

1.1 Create the environment

python3 -m venv .venv

Creates a hidden .venv folder containing the isolated Python environment.

1.2 Activate the environment

source .venv/bin/activate

1.3 Install packages

pip install requests paramiko

1.4 Save dependencies

Python does not auto-generate a dependency file. You must manually export your exact dependency tree to a plain text file named requirements.txt:

pip freeze > requirements.txt

To replicate the exact environment on a production server:

pip install -r requirements.txt

2. How to switch environments

2.1 Deactivate the current environment

deactivate

2.2 Activate the new environment

Change to the project directory, then run:

source .venv/bin/activate

3. Specify the Python version

To use a specific Python version for your project even if it is not installed on your machine, you can use a tool called pyenv.

3.1 Install pyenv

On macOS:

brew install pyenv

On Linux, follow the pyenv installation guide.

3.2 Download the Python version you need

pyenv install 3.11.8

3.3 Configure that version in your current directory

pyenv local 3.11.8

3.4 Create the virtual environment

python -m venv .venv