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This is the code base behind Publican, a prototype small business accounting application for the web.

I have just written this Publican prototype as my entry in the Django Dash 2012. You can currently see a demonstration here:

I have tried to direct my effort towards creating a beautiful and extensible core for further development. There were three main ideas that I wanted this prototype to illustrate.

  • The idea of the timeline that lives on the main page is the vision that first popped into my head, several months ago, and that eventually led to my choosing this project. It is, in miniature, exactly what I need: a view that lets me step back and look at the big picture of what tax obligations are approaching and what I will need to do to satisfy them. Of course, in the vision, there are more than two supported tax forms; but at least this prototype let me assemble all of the working pieces for the first time!

  • The interface that tax-form code uses to traverse business data was another major focus of attention. The last thing I want is to burden the authors of future Publican tax-form modules with a finicky and fragile interface; instead, I want to hide the database from them completely, and give them an easy way to view its data without getting tangled up in ORM details. I also wanted tax-form computation logic to be strongly decoupled from the rest of the application — you will note, if you review the Python code for Form 940 and Form 941, that the interface is completely functional, and persists no state at all between calls. Tax form modules do not even define any classes; they simply define functions, along with a few data structures to support HTML and PDF rendering!

  • The most exciting stunt that I had been looking forward to was filling out and rendering the PDF tax forms themselves. It really surprised me that my scheme worked, on its first try, without any complaint. Some day the process might fall over if we try giving it some obscure state tax form produced by a poor PDF export program, but for federal forms it is a staggeringly clean process. The trick is that it took two separate PDF libraries to make the process so elegant: ReportLab is the expert at producing PDF, but pyPdf is the king when it comes to assembling documents out of other pieces.

You can run the project tests — which currently ignore the web interface and instead exercise the tax form computation logic — by checking the project out and running:

$ python -m unittest

Finally, a note on terminology: a publican was the Roman term for a tax collector. You can think of Publican as an old patrician, well versed in all of the details of tax law, looking over your situation and helping you figure out what needs to be filed next.

Thanks for reading, and let me know if you have any questions!


Prototype small business tax calculation for Django Dash 2012




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