Here, we'll enable the virtualenv package, which will illustrate how to install packages from the PyPI site. We'll also configure our first environment, which we'll use throughout the book for the rest of our examples and code illustrations.
As a user with administrative privileges, install
virtualenvfrom the system command line by runningeasy_install virtualenv. If you have the correct permissions, your output should be similar to the following.Searching for virtualenv Reading http://pypi.python.org/simple/virtualenv/ Reading http://virtualenv.openplans.org Best match: virtualenv 1.4.5 Downloading http://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.4.5.tar.gz#md5=d3c621dd9797789fef78442e336df63e Processing virtualenv-1.4.5.tar.gz Running virtualenv-1.4.5/setup.py -q bdist_egg --dist-dir /tmp/easy_install-rJXhVC/virtualenv-1.4.5/egg-dist-tmp-AvWcd1 warning: no previously-included files matching '*.*' found under directory 'docs/_templates' Adding virtualenv 1.4.5 to easy-install.pth file Installing virtualenv script to /usr/bin Installed /usr/lib/python2.6/site-packages/virtualenv-1.4.5-py2.6.egg Processing dependencies for virtualenv Finished processing dependencies for virtualenv
Drop administrative privileges as we won't need them any longer. Ensure that you're within your home directory and create a new virtual instance by running:
$ virtualenv --no-site-packages text_processingStep into the newly created
text_processingdirectory and activate the virtual environment. Windows users will do this by simply running theScripts\activateapplication, while Linux users must instead source the script using the shell's dot operator.$ . bin/activateIf you've done this correctly, you should now see your command-line prompt change to include the string (
text_processing). This serves as a visual cue to remind you that you're operating within a specific virtual environment.(text_processing)$ pwd /home/jmcneil/text_processing (text_processing)$ which python /home/jmcneil/text_processing/bin/python (text_processing)$
Finally, deactivate the environment by running the deactivate command. This will return your shell environment to default. Note that once you've done this, you're once again working with the system's Python install.
(text_processing)$ deactivate $ which python /usr/bin/python $
Note
If you're running Windows, by default python.exe and easy_install.exe are not placed on your system %PATH%. You'll need to manually configure your %PATH% variable to include C:\Python2.6\ and C:\Python2.6\Scripts. Additional scripts added by easy_install will also be placed in this directory, so it's worth setting up your %PATH% variable.
We installed the virtualenv package using the easy_install command directly off of the Python Package index. This is the method we'll use for installing any third-party packages going forward. You should now be familiar with the easy_install process. Also, note that for the remainder of the book, we'll operate from within this text_processing virtual environment. Additional packages are installed using this same technique from within the confines of our environment.
After the install process was completed, we configured and activated our first virtual environment. You saw how to create a new instance via the virtualenv command and you also learned how to subsequently activate it using the bin/activate script. Finally, we showed you how to deactivate your environment and return to your system's default state.
Now that you know how to set up your own isolated Python environment, you're encouraged to create a second one and install a collection of third-party utilities in order to get the hang of the installation process.
Create a new environment and name it as of your own choice.
Point your browser to http://pypi.python.org and select one or more packages that you find interesting. Install them via the
easy_installcommand within your new virtual environment.
Note that you should not require administrative privileges to do this. If you receive an error about permissions, make certain you've remembered to activate your new environment. Deactivate when complete. Some of the packages available for install may require a correctly configured C-language compiler.