Mahotas: A continuous improvement example

Last week, I tweeted:

Again & again, I find that you don’t get to something good by doing it well from the start, but by constant incremental improvements.

— Luis Pedro Coelho (@luispedrocoelho) July 25, 2013

Let me highlight a good example of continuous improvement in mahotas and the advantages of eating your own dog food.

I was using mahotas to compute some wavelets, but I couldn’t remember the possible parameter values. So I got some error:

[1]: mh.daubechies(im, 'db4')

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-6-2e939df57e6a> in <module>()
----> 1 mh.daubechies(im, 'db4')

/home/luispedro/work/mahotas/mahotas/convolve.pyc in daubechies(f, code, inline)
    492     '''
    493     f = _wavelet_array(f, inline, 'daubechies')
--> 494     code = _daubechies_codes.index(code)
    495     _convolve.daubechies(f, code)
    496     _convolve.daubechies(f.T, code)ValueError: 'db4' is not in list

I could have just looked up the right code and moved on. Instead, I considered the unhelpfulness of the error message a bug and fixed it (here is the commit)

Now we get a better error message:

ValueError: mahotas.convolve: Known daubechies codes are ['D2', 'D4', 'D6',
'D8', 'D10', 'D12', 'D14', 'D16', 'D18', 'D20']. You passed in db4.

You still get an error, but at least it tells you what you should be doing.

Good software works well. Excellent software fails well too.

Related articles

• Mahotas software paper published (metarabbit.wordpress.com)
• Making Your Mistakes in Public (metarabbit.wordpress.com)