python处理二进制数据的一段代码

    #!/usr/env/env python
    #-*- coding: cp936 -*-
    '''''
    add Head Infomation for pcm file
    '''
    import sys
    import struct
    import os
     
    __author__ = 'bob_hu, jbxue123@gmail.com'
    __date__ = 'Dec 19,2011'
    __update__ = 'Dec 19,2011'
     
    def geneHeadInfo(sampleRate,bits,sampleNum):
        '''''
        生成头信息，需要采样率，每个采样的位数，和整个wav的采样的字节数
        '''
        rHeadInfo = 'x52x49x46x46'
        fileLength = struct.pack('i',sampleNum + 36)
        rHeadInfo += fileLength
        rHeadInfo += 'x57x41x56x45x66x6Dx74x20x10x00x00x00x01x00x01x00'
        rHeadInfo += struct.pack('i',sampleRate)
        rHeadInfo += struct.pack('i',sampleRate * bits / 8)
        rHeadInfo += 'x02x00'
        rHeadInfo += struct.pack('H',bits)
        rHeadInfo += 'x64x61x74x61'
        rHeadInfo += struct.pack('i',sampleNum)
        return rHeadInfo
           
    if __name__ == '__main__':
        if len(sys.argv) != 5:
            print "usage: python %s inFile sampleRate bits outFile" % sys.argv[0]
            sys.exit(1)
         
        fout = open(sys.argv[4],'wb') #用二进制的写入模式
        #fout.write(struct.pack('4s','x66x6Dx74x20')) #写入一个长度为4的串，这个串的二进制内容为 66 6D 74 20
        #Riff_flag,afd,fad,afdd, = struct.unpack('4c',fin.read(4)) #读入四个字节，每一个都解析成一个字母
        #open(sys.argv[4],'wb').write(struct.pack('4s','fmt ')) #将字符串解析成二进制后再写入
        #open(sys.argv[4],'wb').write('x3Cx9Cx00x00x57') #直接写入二进制内容：3C 9C 00 00 57
        #fout.write(struct.pack('i',6000)) #写入6000的二进制形式
     
        #check whether inFile has head-Info
        fin = open(sys.argv[1],'rb')
        Riff_flag, = struct.unpack('4s',fin.read(4))
        if Riff_flag == 'RIFF':
            print "%s 有头信息" % sys.argv[1]
            fin.close()
            sys.exit(0)
        else:
            print "%s 没有头信息" % sys.argv[1]
            fin.close()
            #采样率
            sampleRate = int(sys.argv[2])
            #bit位
            bits = int(sys.argv[3])
             
            fin = open(sys.argv[1],'rb')
            startPos = fin.tell()
            fin.seek(0,os.SEEK_END)
            endPos = fin.tell()
            sampleNum = (endPos - startPos)
            print sampleNum
            headInfo = geneHeadInfo(sampleRate,bits,sampleNum)
            fout.write(headInfo)
            fin.seek(os.SEEK_SET)
            fout.write(fin.read())
            fin.close()
            fout.close()