pip and virtualenv a lightning talk for the "Python for beginners" meetup Barcelona 20/03/2014

1. and now, for something completely different…

2. pip & virtualenv
Alex Maneu !
@zouave
@PyBcn 20/03/2014

3. what is this about?
package management
when you need something
someone else has written

4. some examples
SciPy
lxml requests
django pymongo

5. jars gems eggs
(wheels)

6. where to find them?
PyPI
pypi.python.org
Python Package Index

7. pip
Recommended tool for
installing uninstalling upgrading
packages from PyPI

8. pip basic commands
pip install [—-upgrade] <package>
Installs a Python package or upgrades it to the latest
available version.
!
Examples
pip install pymongo=1.2
pip install /some/dir/mypackage.tgz
pip install http://someserver/mypackage.zip
pip install git+ssh://myserver/myrepo.git@feature#egg=MyPackage
!
!
pip uninstall <package>
Deletes an already installed package

9. pip basic commands
pip list [—-outdated]
Lists installed packages
!
!
pip search <string>
Searches for packages whose description contains the
specified string
> pip list --outdated
amqp (Current: 1.3.3 Latest: 1.4.4)
billiard (Current: 3.3.0.8 Latest: 3.3.0.16)
celery (Current: 3.1.5 Latest: 3.1.9)
…
Examples
> pip search cassandra
cqlengine - Cassandra CQL 3 Object Mapper for Python
CassandraLauncher - Command line utilities for launching Cassandra clusters in EC2
pycassa - Python client library for Apache Cassandra
…

10. what happens if…?
> pip install pymongo
!
(…)
error: could not create '/Library/Python/
2.7/site-packages/bson': Permission
denied

11. virtualenv
Tool for creating
Python environments
i s o l a t e d

12. virtualenv
v1 v2 v3
django
lxml
+
site packages
numpy=1.8.0
pymongo
requests>=2.2.0
site packages
pyOpenSSL, pip, numpy=1.6.2

13. creating a virtual env
virtualenv [options] <dest_dir>
Create a new virtual environment at the specified
path. It will contain a copy of all system-wide
packages.
!
Useful options
—-no-site-packages
Create a new empty virtual environment.
—-python=<python path>
Use the specified Python executable.

14. switching to a virtual env
> source <dir>/bin/activate
(v1)>
!
!
Exiting current virtualenv
(v1)> deactivate
>

15. cool stuff with pip +
virtualenv
!
pip freeze > requirements.txt
Create a description file with the packages and
versions installed under the current virtualenv.
!
pip install -r requirements.txt
Install all packages according to the specification
in requirements.txt.

16. summary
• Packages: code someone else has written
(SciPy, Django, lxml, pymongo)
• Find packages on PyPI: pypi.python.org
• Install them using pip
• Keep your environment clean by using
virtualenv

17. Thank you!
questions?