python处理二进制数据的方法

#!/usr/env/env python 
#-*- coding: cp936 -*- 
''''' 
add Head Infomation for pcm file 
''' 
import sys 
import struct 
import os 
__author__ = 'bob_hu, hewitt924@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 = '\x52\x49\x46\x46' 
  fileLength = struct.pack('i',sampleNum + 36) 
  rHeadInfo += fileLength 
  rHeadInfo += '\x57\x41\x56\x45\x66\x6D\x74\x20\x10\x00\x00\x00\x01\x00\x01\x00' 
  rHeadInfo += struct.pack('i',sampleRate) 
  rHeadInfo += struct.pack('i',sampleRate * bits / 8) 
  rHeadInfo += '\x02\x00' 
  rHeadInfo += struct.pack('H',bits) 
  rHeadInfo += '\x64\x61\x74\x61' 
  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','\x66\x6D\x74\x20'))
  #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('\x3C\x9C\x00\x00\x57')
  #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()