7.1. Module venv

7.1.1. Rationale

  • Bundled with Python since 3.3

  • Isolated Python environment

  • Allows to have multiple versions of Python for one project

  • For testing on different versions: py37, py38, py39, py310a1

  • Test libraries and frameworks before upgrading (create venv, install requirements, run tests, delete if fails)

  • Allows to have different versions of libraries and frameworks for each project

7.1.2. Create

  • DIRECTORY is the name of venv folder (see "Directory Naming Convention" below)

$ cd PROJECT
$ python3.9 -m venv DIRECTORY

Example:

$ cd PROJECT
$ python3.9 -m venv venv-3.9.5

7.1.3. Activate

  • Scripts for Windows

  • bin for macOS, Linux, BSD

  • Note the direction of slash and backslash (OS dependent)

Windows:

$ cd PROJECT
$ venv-3.9.5\Scripts\activate.bat

macOS, Linux, BSD:

$ cd PROJECT
$ venv-3.9.5/bin/activate

7.1.4. Directory Naming Convention

  • No standard naming convention

  • Naming directory like module (venv) name is a good idea

  • Adding Python version is also a good practice

  • Optionally naming per main framework/library version

  • Dot at the beginning hides directory on Linux and macOS (but doesn't work on Windows)

  • Underscore is Python convention for private/protected, but does not work for OS and Git

venv/
.venv/
_venv/

virtualenv/
.virtualenv/
_virtualenv/

py
python
py-3.9
python-3.9
python-3.9.5

.py
.python
.py-3.9
.python-3.9
.python-3.9.5

venv-3.6/
venv-3.7/
venv-3.8/
venv-3.9/
venv-3.10/

venv-3.8.0/
venv-3.8.1/
venv-3.8.2/
venv-3.8.3/

venv-3.9.0/
venv-3.9.1/
venv-3.9.2/
venv-3.9.3/
venv-3.9.5/
venv-3.9.5/

venv-3.10-alpha1/
venv-3.10-alpha2/
venv-3.10-beta1/
venv-3.10-beta2/
venv-3.10-rc1/

venv-django-2.1
venv-django-2.2
venv-django-2.3
venv-django-3.0
venv-django-3.1
venv-django-3.2
venv-django-4.0a1
venv-django-4.0a2
venv-django-4.0b1
venv-django-4.0b2
venv-django-4.0rc1
venv-django-4.0rc2

venv-py39-dj33
venv-python39-django33
venv-python310alpha1-django40a1

This convention is from virtualenv-wrapper module (mostly used in Python 2):

~/.virtualenv/PROJECT_NAME/

7.1.5. Good practices

  • name as version venv-3.9.5

  • place in your project directory and add folder to .gitignore (important!)

  • otherwise place it in ~/.virtualenv/, but some meaningful name is required

  • Append at the end of venv-3.9.5/bin/activate:

    project_name='My Project'

red='\[\033[00;31m\]'
green='\[\033[00;32m\]'
blue='\[\033[00;36m\]'
white='\[\033[00;39m\]'

export PS1="\n${blue}${project_name}> ${white}"

7.1.7. Assignments

Todo

Convert assignments to literalinclude

7.1.7.1. Virtualenv

  • Assignment: Virtualenv

  • Complexity: easy

  • Lines of code: 0 lines

  • Time: 2 min

English:

  1. Create venv

  2. Add venv as a Python interpreter in your IDE

  3. Run doctests - all must succeed

Polish:

  1. Stwórz venv

  2. Dodaj venv jako interpreter Python w Twoim IDE

  3. Uruchom doctesty - wszystkie muszą się powieść