by Christian Strappazzon

1. The hitchhicker's guide to PIP
and Virtualenv (wrapper)...
Maybe...

2. Knowing where one's towel is
"Hey, you sass that hoopy Ford Prefect? There's a frood who really
knows where his towel is." (Sass: know, be aware of, meet, have sex
with; hoopy: really together guy; frood: really amazingly together
guy.)

3. Index
PIP virtual
env
r
r appe
l envw
v irtua
mabye...
and e
veryt
hing
:)
wers
ans

4. Prerequisites
It (maybe) works also
in other *nix and
with a little effort on
● Python :) Windows ;)
● linux ( unfortunately or fortunately :P )
● comfort with shell
● patience required
● internet connection ( not now, but we
work on the web, in the coils of the Python! )

5. What is PIP?
- pip installs packages. Python packages. -
pip is a tool for installing and
managing Python packages, such as
those found in the Python Package
Index (PyPI).
It’s a replacement for easy_install.

6. But... what is Easy Install?
Easy Install is a python module
(easy_install) bundled with
setuptools that lets you
automatically download, build, install,
and manage Python packages.

7. So what?
ea
sy
_i
ns
I P ta
P ll

9. PIP installation
Using package manager, the installer or from source
(root)# apt-get install python-pip
# or
(root)# curl http://python-distribute.org/distribute_setup.
py | python
(root)# curl https://raw.github.
com/pypa/pip/master/contrib/get-pip.py | python
# or
$ curl -O http://[...]/pip-1.0.tar.gz
$ tar xvfz pip-x.y.tar.gz ; cd pip-1.0
# or
$ git clone https://github.com/pypa/pip.git ; cd pip
(root)# python setup.py install

10. PIP usage - base options
$ pip install SomePackage
pip install /path/to/SomePackage.1.1.1.tar.gz
pip install http://myrepo.it/SomePakage-1.4.0.zip
pip install -e git+http://github.com/django/django.git#egg=django
pip install -e path/to/SomePackage
pip install django==1.1.1
==, >=, >, <, <=
$ pip install --upgrade package-name
$ pip uninstall package-name another way for
querying installed
packages given from
$ pip search "query" yolk
$ pip freeze > requirements.txt
Django==1.1.2
ipdb==0.2
$ pip install -r requirements.txt ipython==0.10.1
...

11. PIP configuration
- quickest look -
*nix $HOME/.pip/pip.conf [global]
timeout = 60
windows %HOME%pippip.ini [freeze]
timeout = 10
$ export PIP_DEFAULT_TIMEOUT=10 [install]
$ pip install django find-links =
http://mirror.com
Env. variables
override config file
Each command line options have a
PIP_<UPPER_NAME> environment variables
$ pip --default-timeout=60 install django

12. PyPI
- the Python Pakage Index -
PyPI is a repository of software for Python
and currently count 20481 packages.
The PyPI repository provides alternative locations that store the
packages.
[install]
use-mirrors = true
$ pip --use-mirrors ... mirrors =
$ export PIP_USE_MIRRORS=true http://d.pypi.python.org
http://b.pypi.python.org
You can create your own mirror, following the PEP 381 or using a tool
such as pep381client

13. Want to know more?
Read the docs!
( Luke! :D )
PIP
http://www.pip-installer.org/en/latest/index.html

14. WHY virtual environments?
● Isolation - Python packages and even version live
in their own 'planet' :)
● Permissions - No sudoers, the environment is
mine!!!
● Organization - each project can maintain its own
requirements file of Python packages.
● No-Globalization - don't require installing stuff
globally on the system.

15. PIP + virtualenv
● it's not recommended install packages
globally, but you can :)
● pip works fine with virtualenv!
● used in conjunction to isolate your
installation
Well... step forward: setup and play with
virtual environments!

16. What is virtualenv?
Is a tool to create isolated Python
environments.
Every virtualenv has pip installed in
it automatically (also easy_install)
under bin directory.
Does not require root access or
modify your system.

17. Installation
Using package manager, pip, the installer or using single file
(root)# apt-get install python-virtualenv
# or
(root)# pip install virtualenv
# or
$ curl -O
https://raw.github.com/pypa/virtualenv/master/virtualenv.py

18. Basic Usage
$ virtualenv ENV
This creates a folder ENV in the $PWD
You'll find python packages on ENV/lib/pythonX.X/site-packages
Interesting options!
$ virtualenv --no-site-packages --python=PYTHON_EXE ENV
Doesn't inherit global site-packages and use a different Python interpreter

19. Activate and Using ENV
$ cd ENV ; . bin/activate
(ENV) $ pip install django
Downloading/unpacking django
Downloading Django-1.4.tar.gz (7.6Mb): 5.2Mb downloaded
...
Also virtualenv has a config file
and its looks like pip.conf

20. Extending virtualenv
# django-day.py
import virtualenv, textwrap
output = virtualenv.create_bootstrap_script(textwrap.
dedent())"""
def after_install(options, home_dir):
subprocess.call([join(home_dir, 'bin', 'pip'),
'install',
'django'])
"""
f = open('django-bootstrap.py', 'w').write(output)
extend_parser(optparse_parser):
# add or remove option The script created is an
adjust_options(options, args):
# change options or args
extension to virtualenv
after_install(options, home_dir): and inherit all its options!
# after install run this

22. virtualenvwrapper
by Doug Hellmann
is a set of extensions to Ian Bicking’s
virtualenv tool for creating isolated
Python development environments.
Features, taken verbatim from website:
● Organizes all of your virtual environments in one place.
● Wrappers for managing your virtual environments (create, delete, copy).
● Use a single command to switch between environments.
● Tab completion for commands that take a virtual environment as argument.
● User-configurable hooks for all operations.
● Plugin system for more creating sharable extensions. Your homework ;)

23. Installation
(root)# pip install virtualenvwrapper
$ cd ~
$ mkdir ~/.virtualenvs
Include environment vars needed into ~/.bashrc
export WORKON_HOME=$HOME/.virtualenvs
source /usr/local/bin/virtualenvwrapper.sh
export PIP_VIRTUALENV_BASE=$WORKON_HOME
export PIP_RESPECT_VIRTUALENV=true
A little tips: add to ~/.virtualenvs/postactivate
export PYTHONPATH=$PYTHONPATH:$VIRTUAL_ENV

24. Basic Commands
A brief introducion to manage virtual enviroment
$ mkvirtualenv --no-site-packages --python=PYTHON_EXE ENV
# same as virtualenv!
$ workon ENV (ENV) $ cdvirtualenv
# set virtualenv environment # go to home environment
(ENV) $
(ENV) $ deactivate
# deactivate current environment
$ rmvirtualenv ENV
# remove selected environment

25. More Commands :)
(ENV) $ lssitepackages
# list packages on current environment
(ENV) $ cdsitepackages
# go to site-packages directory
(ENV) $ add2virtualenv directory...
# adds the specified directories to the Python path
(ENV) $ toggleglobalsitepackages
# enable/disable global site-packages
Much more commands & options at
http://www.doughellmann.com/docs/virtualenvwrapper/command_ref.html

26. Simple Sample :P
$ mkvirtualenv --no-site-packages djangoday-rulez
(djangoday-rulez) $ deactivate
$ workon djangoday-rulez
(djangoday-rulez) $ cdvirtualenv
(djangoday-rulez) $ pip install django
... do some cool stuff ...
(djangoday-rulez) $ lssitepackages
(djangoday-rulez) $ deactivate
... do other stuff or switch project
... --- ...
... if it's not so cool ;) ...
$ rmvirtualenv djangoday-rulez

27. Tips & Hooks
virtual environment with "requirements.txt" file
$ mkvirtualenv --no-site-packages
--python=PYTHON_EXE -r django-requirements.txt
$ mkvirtualenv --no-site-packages
-r other-requirements.txt
Under ~/.virtualenvs you'll find the hook scripts that running pre/post
create, activate environments.
postmkvirtualenv
Hooks are simply plain-text files with shell commands. prermvirtualenv
You can customize them to change their behavior when an postrmvirtualenv
postactivate
event occurs. predeactivate
postdeactivate
See extending virtualenv-wrapper: http://bit.ly/IMP0vh

28. Not entirely unlike...
virtualenv virtualenvwrapper
http://bit.ly/141dCr
http://bit.ly/jbFVCe

29. which python ?
Latest stable
2.4.6, 2.5.6,
2.6.8, 2.7.3
Images comes from
Wikipedia

31. pythonbrew !
pythonbrew is a program to automate the
building and installation of Python in the
users $HOME.

32. Installation
Recommended way
$ curl -kL http://xrl.us/pythonbrewinstall | bash
Add the following line into ~/.bashrc
[[ -s $HOME/.pythonbrew/etc/bashrc ]] && source $HOME/.
pythonbrew/etc/bashrc
Last News!!!
The original project seems to be unmantained, but there is
a fork https://github.com/saghul/pythonz
(forked last week... Wait! I have a presentation to do! :D )
Long live pythonz!

33. Usage
Crash course!
$ pythonbrew install VERSION $ pythonbrew off
# install python VERSION # turn off pythonbrew
$ pythonbrew list -k $ pythonbrew use VERSION
# list available pythons # use specified python
$ pythonbrew list $ pythonbrew uninstall VERSION
# list installed pythons # uninstall python VERSION
$ pythonbrew switch VERSION
# permanently use specified python

34. which python
$ pythonbrew use 2.6.5
$ which python
/home/cstrap/.pythonbrew/pythons/Python-2.5.6/bin/python
$ pythonbrew off
$ which python
/usr/bin/python
Cool! And you can create isolated python environments
(it uses virtualenv) ...

35. Create and use pythonbrew
Always use
the --force,
Luke!
$ pythonbrew install --force 2.5.6
... wait... This could take a while...
$ pythonbrew use 2.5.6
$ pythonbrew venv init
$ pythonbrew venv create djangoday-proj
$ pythonbrew venv list # list all environments
$ pythonbrew venv use djangoday-proj
(djangoday-proj) $ pip install django
... do some cool stuff ...
... if it's not so cool ;) ...
$ pythonbrew venv delete djangoday-proj

36. Mostly Harmles...
● virtualenv & virtualenvwrapper
allow you to create and manage
environments using the system default
Python interpreter
● pythonbrew allow you to install
different Python interpreter, create
and manage virtual environments
...

38. Basic Combo
$ pythonbrew install --force 2.6.7
... wait...
$ mkvirtualenv --no-site-packages
-p $HOME/.pythonbrew/pythons/Python-2.6.7/bin/python
djangoDay
... wait...
(djangoDay) $ cdvirtualenv
(djangoDay) [djangoDay] $ pip install django
... wait...
(djangoDay) $ which python ; python -V
/home/cstrap/.virtualenvs/djangoDay/bin/python
Python 2.6.7
(djangoDay) [djangoDay] $ deactivate
$ which python ; python -V
/usr/bin/python
Python 2.7.2

39. Super Combo
$ pythonbrew install --force 2.7.3 ... wait...
$ pythonbrew install --force 2.5.6 ... wait...
$ pythonbrew use 2.7.3
$ pip install virtualenv && pip install virtualenvwrapper
# configure .bashrc
export WORKON_HOME=$HOME/.virtualenvs
export
VIRTUALENVWRAPPER_PYTHON=$HOME/.pythonbrew/pythons/Python-2.7.3/bin/python
source $HOME/.pythonbrew/pythons/Python-2.7.3/bin/virtualenvwrapper.sh
export PIP_VIRTUALENV_BASE=$WORKON_HOME
$ mkdir ~/.virtualenvs
$ mkvirtualenv --no-site-packages
-p $HOME/.pythonbrew/pythons/Python-2.5.6/bin/python djangoDay
(djangoDay) $ which python ; python -V
/home/cstrap/.virtualenvs/djangoDay/bin/python
Python 2.5.6
(djangoDay) [djangoDay] $ deactivate
$ which python ; python -V
/home/cstrap/.pythonbrew/pythons/Python-2.7.3/bin/python
Python 2.7.3
$ pythonbrew off; python -V
# Your current system version of Python

40. Share and Enjoy! :P

41. lab@strap.it
@cstrap

42. Answers?
Thanks for your patience! ;)