import base64, wave, array

# Input ...

h = open("data")
a = array.array("c", base64.b64decode(h.read()))
a.byteswap()
h.close()

# ... Processing ...

h = wave.open("modified.wav", "wb")
h.setnchannels(1)
h.setsampwidth(1)
h.setframerate(22050)

# ... Output

h.writeframes(a.tostring())
h.close()