Can't write floating point aiff file in Python

Question

I'm an audio developer and would like to read and write 32 bit floating point audio files from python for test purposes. After hours of farting around, I've managed to realize that the problems I'm having are restricted to the floating point format. I can successfully write a 16 bit fixed point file from a numpy array (even though there are no examples in the aifc documentation).

I also saw a couple other libraries PySoundFile and Audiolab, though they were either really old and/or didn't install properly.

What is the right way to get this done in python? There are a shocking lack of google results on the subject of writing sound files in python.

The following code does not work, but is based on very similar code which does work for 16 bit fixed point data.

 def write_test_float_aiff(data):
   f = aifc.open('test.aiff', 'w')
   f.setframerate(44100)
   f.setnchannels(1)
   f.setsampwidth(4)
   f.writeframes(data)
   f.close()

r = np.arange(0,1000,.1)
s = np.sin(r)
write_test_float_aiff(s.byteswap().tostring())