A virtual environment is an isolated Python environments. It has it's own
installed site-packages which can be different from the systems
site-packages.
TL;DR: pipenv is your friend; it allows you to forget about the others.
virtualenv
virtualenv was created by Ian Bicking. The first version on PyPI is from
2007.
pyvenv
Was deprecated in favour of python -m venv. It was removed with Python 3.8.
venv
The venv module was
added in Python 3.3 with PEP 405
(2012).
pyenv
pyenv lets you switch between multiple versions of Python.
Installation: See GitHub
Usage:
$ pyenv install --list
Available versions:
2.1.3
[...]
3.8.1
3.9-dev
activepython-2.7.14
activepython-3.5.4
activepython-3.6.0
anaconda-1.4.0
[... a lot more; including anaconda, miniconda, activepython, ironpython, pypy, stackless, ....]
$ pyenv install 3.8.1
Downloading Python-3.8.1.tar.xz...
-> https://www.python.org/ftp/python/3.8.1/Python-3.8.1.tar.xz
Installing Python-3.8.1...
Installed Python-3.8.1 to /home/moose/.pyenv/versions/3.8.1
$ pyenv versions
* system (set by /home/moose/.pyenv/version)
2.7.16
3.5.7
3.6.9
3.7.4
3.8-dev
$ python --version
Python 2.7.17
$ pip --version
pip 19.3.1 from /home/moose/.local/lib/python3.6/site-packages/pip (python 3.6)
$ mkdir pyenv-experiment && echo "3.8.1" > "pyenv-experiment/.python-version"
$ cd pyenv-experiment
$ python --version
Python 3.8.1
$ pip --version
pip 19.2.3 from /home/moose/.pyenv/versions/3.8.1/lib/python3.8/site-packages/pip (python 3.8)
pipenv
pipenv automatically creates and manages a
virtualenv for your projects, as well as adds/removes packages from your
Pipfile as you install/uninstall packages. It also generates the Pipfile.lock,
which is used to produce deterministic builds. It helps creating reproducible
environments.
pipenv uses virtualenv and pyenv.
Usage
First, create a virtual environment:
$ pipenv --python 3.8
Creating a virtualenv for this project…
Pipfile: /home/moose/GitHub/clana/Pipfile
Using /home/moose/.pyenv/versions/3.8.1/bin/python3.8 (3.8.1) to create virtualenv…
⠏ Creating virtual environment...Already using interpreter /home/moose/.pyenv/versions/3.8.1/bin/python3.8
Using base prefix '/home/moose/.pyenv/versions/3.8.1'
New python executable in /home/moose/.local/share/virtualenvs/clana-oPEDiD9W/bin/python3.8
Also creating executable in /home/moose/.local/share/virtualenvs/clana-oPEDiD9W/bin/python
Installing setuptools, pip, wheel...
done.
Running virtualenv with interpreter /home/moose/.pyenv/versions/3.8.1/bin/python3.8
✔ Successfully created virtual environment!
Virtualenv location: /home/moose/.local/share/virtualenvs/clana-oPEDiD9W
requirements.txt found, instead of Pipfile! Converting…
✔ Success!
Warning: Your Pipfile now contains pinned versions, if your requirements.txt did.
We recommend updating your Pipfile to specify the "*" version, instead.
Activate the environment:
$ pipenv shell
Launching subshell in virtual environment…
. /home/moose/.local/share/virtualenvs/clana-oPEDiD9W/bin/activate
$ pip --version
pip 20.0.2 from /home/moose/.local/share/virtualenvs/clana-oPEDiD9W/lib/python3.8/site-packages/pip (python 3.8)
Set your Pipfile.lock:
$ pipenv lock
Locking [dev-packages] dependencies…
Locking [packages] dependencies…
✔ Success!
Updated Pipfile.lock (310e7d)!
Make sure your environment has exactly the stuff installed that you need:
$ pipenv sync
Installing dependencies from Pipfile.lock (310e7d)…
🐍 ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 14/14 — 00:00:06
All dependencies are now up-to-date!
Docker
If you want more isolation, have a look at Docker.
I use the python:3.8-slim-buster (February 2020).
The Dockerfile can then look like this:
FROM python:3.8-slim-buster
# Update and install extra packages
RUN apt-get update && apt-get install -y git build-essential
# Install project dependencies
COPY requirements.txt /opt/app/requirements.txt
WORKDIR /opt/app
RUN pip install -r requirements.txt
# Install project
COPY . /opt/app
RUN pip install . --no-deps