Python Audio library for fast, gapless looping of many short audio tracks
I am using PyAudio for a lot of things and are quite happy with it. If it can do this, I do not know, but I think it can. 
One solution is to feed sound buffer manually and control / set the needed latency. I have done this and it works quite well. If you have the latency high enough it will work. 
An other solution, similar to this, is to manage the latency your self. You can queue up and or mix your small sound files manually to e.g. sizes of 0.5 -1 sec. This will greatly reduce the requirement to the "realtimeness" and alow you to do some pretty cool transitions between "speeds" 
I do not know what sort of latency you can cope with, but if we are talking about train speeds, I guess they do not change instantaneous - hence latency of 500ms to several seconds is most likely acceptable.
I'm writing an application to simulate train sounds. I got very short (0.2s) audio samples for every speed of the train and I need to be able to loop up to 20 of them (one for every train) without gaps at the same time.
Gapless changing of audio samples (train speed) is also a Must-Have.
I've been searching for possible python-audio-solutions, including

PyAudio
PyMedia
pyaudiere

but I'm not sure which one suits best my use-case, so I do really appreciate any propositions and experiences!
PS: I did already try out gstreamer but since the 1.0 release is not there yet and I cant figure out how to get gapless playback to work with pygi, i thought there might be a better choice. I also tried pygame, but it seems like it's limited to 8 audio channels??