If I have an MP3 file how can I convert it to a WAV file? (preferably, using a pure python approach)
Answer
I maintain an open source library, pydub, which can help you out with that.
from pydub import AudioSegment
sound = AudioSegment.from_mp3("/path/to/file.mp3")
sound.export("/output/path/file.wav", format="wav")
One caveat: it uses ffmpeg to handle audio format conversions (except for wav files, which python handles natively).
note: you probably shouldn't do this conversion on GAE :/ even if it did support ffmpeg. EC2 would be a good match for the job though