Official documentation at: https://packaging.python.org/en/latest/tutorials/installing-packages/#creating-and-using-virtual-environments.

There are two common tools for creating Python virtual environments:

• venv is available by default in Python 3.3 and later, and installs pip and setuptools into created virtual environments in Python 3.4 and later.
• virtualenv needs to be installed separately, but supports Python 2.7+ and Python 3.3+, and pip, setuptools and wheel are always installed into created virtual environments by default (regardless of Python version).

# to enable
export DIR=.venv
python3 -m venv "$DIR"
source "$DIR"/bin/activate
# to disable
deactivate

export DIR=.venv
python3 -m virtualenv "$DIR"
source "$DIR"/bin/activate

Using Python environments in VS Code: https://code.visualstudio.com/docs/python/environments.