Installing Requirements

Let’s get our tutorial environment setup. Most of the setup work is in standard Python development practices (install Python, make an isolated environment, and setup packaging tools.)

This Quick Tutorial is based on:

• Python 2.7.
• setuptools and easy_install. We use setuptools and its easy_install for package management.
• Virtual environment. Our home directory will contain a Python virtual environment that we’ll use to run commands, and which will also serve as a directory in which we can dump stuff.
• Unix commands. Commands in this tutorial use UNIX syntax and paths. Windows users should adjust commands accordingly, although examples are given for Windows users in this chapter too.

Install Python 2.7

If you use Linux or Mac OS X, download the latest standard Python 2.7 release (not development release) from python.org.

Windows users should also install the Python for Windows extensions. Carefully read the README.txt file at the end of the list of builds, and follow its directions. Make sure you get the proper 32- or 64-bit build and Python version.

Linux users can either use their package manager to install Python 2.7 or may build Python 2.7 from source.

Set an Environment Variable

This tutorial will refer frequently to the location of the virtual environment. We set an environment variable to save typing later.

Mac OS X and Linux:

$ export VENV=~/pytesting

Windows:

c:\> set VENV=c:\pytesting

Install setuptools (Python packaging tools)

The following command will download a script to install setuptools, then pipe it to your environment’s version of Python.

On Mac OS X or Linux:

$ wget --no-check-certificate https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py -O - | $VENV/bin/python

On Windows:

# Use your web browser to download this file:
# https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py
# ...and save it to c:\ez_setup.py
# Then run the following command:

c:\> %VENV%\Scripts\python ez_setup.py

Create a Virtual Environment

virtualenv is a tool to create isolated Python 2.7 environments, each with its own Python binary and independent set of installed Python packages. Let’s install virtualenv.

Mac OS X and Linux:

$ sudo easy_install virtualenv

Windows:

c:\> c:\Python27\Scripts\easy_install virtualenv

Let’s create a virtualenv, using the location we just specified in the environment variable.

Mac OS X or Linux:

$ virtualenv $VENV

Windows:

c:\> c:\Python27\Scripts\virtualenv %VENV%

Activate Your Virtual Environment

“Activate” your virtual environment so that when you type python, it means “execute my virtual environment’s Python interpreter instead of the system Python interpreter”:

On Linux/Mac OS X:

$ source ~/pytesting/bin/activate

On Windows:

c:> c:/pytesting/Scripts/activate

Checking It’s Working

Execute:

$ python -c "import sys; print sys.prefix"

It should spit out something like:

``/home/chrism/pytesting``

Or, on Windows:

``c:\pytesting``

If instead, it spits out anything like /usr or c:\, it’s not activated properly.

Conclusion

We’re now ready to go.

We’ll be putting all the files we create into ~/pytesting (Linux/Mac) or c:\pytesting (Windows) from here on in.

There will be a bin (or Scripts on Windows) dir in the directory, a lib dir, and possibly an include dir in there. No worries, we’ll put the files and directories we create next to those. Just don’t accidentally delete them.

Why Not Python 3?

Cars.com uses Python 2.7 primarily, so that’s what we’re using in this class. That said, almost all of the examples, code snippets, and frameworks used in this class will work as-is under Python 3, so you won’t need to relearn much when you move to that version.