[py] improve style for demo_filterbank.py

diff --git a/python/demos/demo_filterbank.py b/python/demos/demo_filterbank.py
index 54aff57..ec29d11 100755 (executable)
--- a/python/demos/demo_filterbank.py
+++ b/python/demos/demo_filterbank.py
@@ -1,30 +1,44 @@
 #! /usr/bin/env python
 
-from aubio import filterbank, fvec
-from pylab import loglog, show, xlim, ylim, xlabel, ylabel, title
-from numpy import vstack, arange
+"""Create a filterbank from a list of frequencies.
 
-win_s = 2048
+This demo uses `aubio.filterbank.set_triangle_bands` to build a set of
+triangular filters from a list of frequencies.
+
+The filterbank coefficients are then modified before being displayed."""
+
+import aubio
+import numpy as np
+import matplotlib.pyplot as plt
+
+# sampling rate and size of the fft
 samplerate = 48000
+win_s = 2048
 
+# define a list of custom frequency
 freq_list = [60, 80, 200, 400, 800, 1600, 3200, 6400, 12800, 24000]
+# number of filters to create
 n_filters = len(freq_list) - 2
 
-f = filterbank(n_filters, win_s)
-freqs = fvec(freq_list)
+# create a new filterbank
+f = aubio.filterbank(n_filters, win_s)
+freqs = aubio.fvec(freq_list)
 f.set_triangle_bands(freqs, samplerate)
 
+# get the coefficients from the filterbank
 coeffs = f.get_coeffs()
-coeffs[4] *= 5.
-
+# apply a gain to fifth band
+coeffs[4] *= 6.
+# load the modified coeffs into the filterbank
 f.set_coeffs(coeffs)
 
-times = vstack([arange(win_s // 2 + 1) * samplerate / win_s] * n_filters)
-title('Bank of filters built using a simple list of boundaries\nThe middle band has been amplified by 2.')
-loglog(times.T, f.get_coeffs().T, '.-')
-xlim([50, samplerate/2])
-ylim([1.0e-6, 2.0e-2])
-xlabel('log frequency (Hz)')
-ylabel('log amplitude')
-
-show()
+# display the band gains in a loglog plot
+freqs = np.vstack([np.arange(win_s // 2 + 1) * samplerate / win_s] * n_filters)
+plt.title('filterbank built from a list of frequencies\n'
+          'The 5th band has been amplified by a factor 6.')
+plt.loglog(freqs.T, f.get_coeffs().T, '.-')
+plt.xlim([50, samplerate/2])
+plt.ylim([1.0e-6, 2.0e-2])
+plt.xlabel('log frequency (Hz)')
+plt.ylabel('log amplitude')
+plt.show()