Python Environment (notes)

(Snippets taken from the Python Manual)
To create a virtual environment, decide upon a directory where you want to place it, and run the venvmodule as a script with the directory path:

python3 -m venv tutorial-env

This will create the tutorial-env directory if it doesn’t exist, and also create directories inside it containing a copy of the Python interpreter, the standard library, and various supporting files.

Once you’ve created a virtual environment, you may activate it. On Unix or MacOS, run:

source tutorial-env/bin/activate

(This script is written for the bash shell. If you use the csh or fish shells, there are alternateactivate.csh and activate.fish scripts you should use instead.)

Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using, and modify the environment so that running python will get you that particular version and installation of Python.

Managing Packages with PIP

From within the virtual environment:

(tutorial-env) $ python -m pip install novas
(tutorial-env) $ python -m pip install requests==2.6.0
(tutorial-env) $ python -m pip install --upgrade requests

pip uninstall followed by one or more package names will remove the packages from the virtual environment.
pip show will display information about a particular package
pip list will display all of the packages installed in the virtual environment
pip freeze will produce a similar list of the installed packages, but the output uses the format that pip install expects

(tutorial-env) $ pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
(tutorial-env) $ python -m pip install -r requirements.txt

To run a script without pre-loading the virtual environment

tutorial-env/bin/python script.py

Or, using the activate script:

tutorial-bin/bin/activate
python script.py