Modules, packages, oh my!!

In this third phase, we chop up our original election_results.py module into a legitimate Python package. The new directory structure is (hopefully) self-explanatory:

├── elex3
│   ├── __init__.py
│   ├── lib
│   │   ├── __init__.py
│   │   ├── parser.py
│   │   ├── scraper.py
│   │   └── summary.py
│   ├── scripts
│   │   └── save_summary_to_csv.py
│   └── tests
│       ├── __init__.py
│       ├── sample_results.csv
│       ├── sample_results_parsed.json
│       ├── sample_results_parsed_tie_race.json
│       ├── test_parser.py
│       └── test_summary.py

• lib/ contains re-usable bits of code.
• scripts/ contains...well..scripts that leverage our re-usable code.
• tests/ contains tests for re-usable bits of code and related fixtures.

Note that we did not change any of our functions. Mostly we just re-organized them into new modules, with the goal of grouping related bits of logic in common-sense locations. We also updated imports and “namespaced” them of our own re-usable code under elex3.lib.

Here’s where we start seeing the benefits of the tests we wrote in the elex2 phase. While we’ve heavily re-organized our underlying code structure, we can run the same tests (with a few minor updates to import statements) to ensure that we haven’t broken anything.

Note: You must add the refactoring101 directory to your PYTHONPATH before any of the tests or script will work.

$ cd /path/to/refactoring101
$ export PYTHONPATH=`pwd`:$PYTHONPATH

$ nosetests -v elex3/tests/*.py
$ python elex3/scripts/save_summary_to_csv.py

Check out the results of the save_summary_to_csv.py command. The new summary_results.csv should be stored inside the elex3 directory, and should match the results file produced by elex2/election_results.py.

Questions

• Do you like the package structure and module names? How would you organize or name things differently?
• Why is it necessary to add the refactoring101/ directory to your PYTHONPATH?
• What are three ways to add a library to the PYTHONPATH?
• What is a class? What is a method?
• What is an object in Python? What is an instance?
• What is the init method on a class used for?
• What is self and how does it relate to class instances?

Exercises

• Look at the original results data, and model out some classes and methods to reflect “real world” entities in the realm of elections.
• Examine functions in lib/ and try assigning three functions to one of your new classes.
• Try extracting logic from the summarize function and re-implement it as a method on one of your classes.