unpack需要一个长度为2

Question

我无法弄清楚我的代码是什么问题

import wave,struct,math

waveFile = wave.open("F:/mayaSound/ChillingMusic.wav", "rb") 
volume = []

frames = waveFile.getnframes()
rate = waveFile.getframerate()
length = frames / int(rate)


for i in range (0,length):
    waveData = waveFile.readframes(1)

    data = struct.unpack("<h",waveData)
    temp = (int(data[0])-128) / 128
    volume.append(20*math.log10(abs(temp) + 1))


print volume

waveFile.close() 

它给了我

Error: error: file <maya console> line 14: unpack requires a string argument of length 2 #