Python内建模块struct实例详解

#!/usr/bin/python# -*- coding:utf-8 -*-'''测试struct模块'''from struct import *import arraydef fun_calcsize():  print 'ci:',calcsize('ci')#计算格式占内存大小  print '@ci:',calcsize('@ci')  print '=ci:',calcsize('=ci')  print '>ci:',calcsize('>ci')  print '<ci:',calcsize('<ci')  print 'ic:',calcsize('ic')#计算格式占内存大小  print '@ic:',calcsize('@ic')  print '=ic:',calcsize('=ic')  print '>ic:',calcsize('>ic')  print '<ic:',calcsize('<ic')def fun_pack(Format,msg = [0x11223344,0x55667788]):  result = pack(Format,*msg)  print 'pack'.ljust(10),str(type(result)).ljust(20),  for i in result:    print hex(ord(i)), # ord把ASCII码表中的字符转换成对应的整形,hex将数值转化为十六进制  print  result = unpack(Format,result)  print 'unpack'.ljust(10),str(type(result)).ljust(20),  for i in result:    print hex(i),  print def fun_pack_into(Format,msg = [0x11223344,0x55667788]):  r = array.array('c',' '*8)#大小为8的可变缓冲区,writable buffer  result = pack_into(Format,r,0,*msg)  print 'pack_into'.ljust(10),str(type(result)).ljust(20),  for i in r.tostring():    print hex(ord(i)),  print  result = unpack_from(Format,r,0)  print 'pack_from'.ljust(10),str(type(result)).ljust(20),  for i in result:    print hex(i),  printdef IsBig_Endian():  '''判断本机为大/小端'''  a = 0x12345678  result = pack('i',a)#此时result就是一个string字符串，字符串按字节同a的二进制存储内容相同。  if hex(ord(result[0])) == '0x78':    print '本机为小端'  else:    print '本机为大端'def test():  a = '1234'  for i in a:    print '字符%s的二进制:'%i,hex(ord(i))#字符对应ascii码表中对应整数的十六进制  '''  不用unpack()返回的数据也是可以使用pack()函数的,只要解包的字符串符合解包格式即可,  pack()会按照解包格式将字符串在内存中的二进制重新解释(说的感觉不太好...,见下例)  '''  print '大端:',hex(unpack('>i',a)[0])#因为pack返回的是元组,即使只有一个元素也是元组的形式  print '小端:',hex(unpack('<i',a)[0])if __name__ == "__main__":  print '判断本机是否为大小端?',  IsBig_Endian()  fun_calcsize()  print '大端:'  Format = ">ii"  fun_pack(Format)  fun_pack_into(Format)  print '小端:'  Format = "<ii"  fun_pack(Format)  fun_pack_into(Format)  print 'test'  test()  '''  result:  判断本机是否为大小端? 本机为小端  ci: 8  @ci: 8  =ci: 5  >ci: 5  <ci: 5  ic: 5  @ic: 5  =ic: 5  >ic: 5  <ic: 5  大端:  pack    <type 'str'>     0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88  unpack   <type 'tuple'>    0x11223344 0x55667788  pack_into <type 'NoneType'>  0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88  pack_from <type 'tuple'>    0x11223344 0x55667788  小端:  pack    <type 'str'>     0x44 0x33 0x22 0x11 0x88 0x77 0x66 0x55  unpack   <type 'tuple'>    0x11223344 0x55667788  pack_into <type 'NoneType'>  0x44 0x33 0x22 0x11 0x88 0x77 0x66 0x55  pack_from <type 'tuple'>    0x11223344 0x55667788  test  字符1的二进制: 0x31  字符2的二进制: 0x32  字符3的二进制: 0x33  字符4的二进制: 0x34  大端:0x31323334  小端:0x34333231  '''