Pip, Virtualenv, VirtualenvWrapper and other tools help isolate Python environments and dependencies to make project management and collaboration easier. Virtualenv creates isolated Python environments and VirtualenvWrapper provides additional tools to manage these environments. These tools help avoid issues with system packages conflicting with project packages, allow installing packages without sudo, and keep different projects and developers on the same page.

1. Pip, Virtualenv,
VirtualenvWrapper &
More
Django District
Wednesday, Nov. 7, 2012
Jackie Kazil
@jackiekazil

2. Where we all start
● easy_install Globally
● And it works! Yay!
● But then....
○ dependencies or versions
○ coordination w/ other developers
○ keeping different systems on same page
○ breaking sys python

3. Case study: Dependencies
Once upon a time in city, much like this one,
there was a newspaper...
….. over 90 Django applications updated
from 0.96 to 1.1.

4. Case study: Breaking sys python
From stackoverflow...
"Is there a way to ensure I can clean everything
up and start from zero?"
"If you remove everything in these 2 directories,
it should clear out all modules...."

5. Why Pip & Virtualenv
● Isolate
○ System packages from project packages
○ Projects from each other
● No sudo required - sys python requires sudo
access, project python doesn’t

6. Becoming the standard...
Pep 405
Python 3.3
http://www.python.org/dev/peps/pep-0405
"... proposes to add to Python a mechanism for
lightweight "virtual environments" with their own
site directories, optionally isolated from system
site directories...."

7. What is...
● pip - replaces easy_install
● virtualenv - creates isolated python
environments
● virtualenvwrapper - to be explained later

8. Basic setup
$ sudo easy_install pip
$ sudo pip install virtualenv
$ sudo pip install virtualenvwrapper
Add to bash settings...
source /usr/local/bin/virtualenvwrapper.sh
export WORKON_HOME=$HOME/.virtualenvs

9. Make environment
$ mkvirtualenv foo
You can add more to this... like setting python
version.
$ mkvirtualenv --python=python2.7

10. What is virtualenvwrapper?
Helps make things easier...
workon foo
vs
source ~/.virtualenvs/foo/bin/activate

11. Installing libraries
pip install django
pip install -r requirements.txt
pip install -U django

12. Where does it live? ~/.virtualenv/foo/...
…/bin
Binaries in your env. Example: ipython
.../include
Dev headers used by the #include directive in C.
…/lib
Where all your python libraries will live
lib/python2.7/site-packages
.../share
Mans & Docs

13. Wrappers
● mkvirtualenv (calls hooks)
● rmvirtualenv
● workon (calls hooks)
● add2virtualenv
● cdsitepackages
● cdvirtualenv
● deactivate (calls hooks)

14. Hooks
● postmkvirtualenv
● prermvirtualenv
● postrmvirtualenv
● postactivate
● predeactivate
● postdeactivate

15. Hook example: postactivate
proj_name=$(echo $VIRTUAL_ENV|awk -F'/' '{print $NF}')
if [ $proj_name = "foo" ]; then
cd /opt/foo/core/
export DJANGO_SETTINGS_MODULE='settings.
dev_settings'
echo "DJANGO_SETTINGS_MODULE set to:"
$DJANGO_SETTINGS_MODULE
fi

16. Hooks example: postmkvirtualenv
https://gist.github.com/4034103

17. Other helpful stuff
pip freeze
pip freeze > requirements.txt
yolk -l
python -c "import sys,pprint;pprint.pprint(sys.
path)"

18. More... virtualenv-burrito
https://github.com/brainsik/virtualenv-burrito
With one command.... BAM! (or maybe not)
... a virtualenv & virtualenvwrapper environment

19. More... virtualenv-tools
https://github.com/fireteam/virtualenv-tools
"This repository contains scripts we're
using at Fireteam for our deployment of
Python code."

20. More... Tox http://tox.testrun.org/latest/
Tox as is a generic virtualenv management and test
command line tool you can use for:
● checking your package installs correctly with different
Python versions and interpreters
● running your tests in each of the environments,
configuring your test tool of choice
● acting as a frontend to Continuous Integration servers,
greatly reducing boilerplate and merging CI and shell-
based testing.

21. More .... Keeping things fresh
Autoenv
https://github.com/kennethreitz/autoenv
"Magic per-project shell environments. Very pretentious."
Bundle Scout
http://bundlescout.com/
"Daily emails keep you on top of the latest updates from
your favorite libraries."

22. More .... Keeping things fresh
(cont)
Pip Lint
https://github.com/dcramer/piplint
"Piplint validates your current environment with the
requirements files you've specified."
Pip Tools
https://github.com/nvie/pip-tools
"A set of two command line tools to help you keep your pip-
based packages fresh, even when you've pinned them"

23. The End
Me: Jackie Kazil, @jackiekazil
W/ contributions from...
Chris Adams, @acdha
&
Members of Django-District :-)
http://www.django-district.org/