square wave python

import wave
w = wave.open('sig.wav', 'r')
newwave = wave.open('sig2.wav','w')
for i in range(w.getnframes()):
    frame = w.readframes(i)


    for j in range(len(frame)):
        # check if amplitude is greater than 0
        if (ord(frame[j]) > 0
            newwave.writeframes(MAX_AMPLITUDE)
		else if (ord(frame[j]) < 0
            newwave.writeframes(MIN_AMPLITUDE)
		else
	    newwave.writeframes(0)

newwave.close()
w.close()