Python二进制数据读取

Question

urllib2请求接收二进制响应，如下所示：

00 00 00 01 00 04 41 4D 54 44 00 00 00 00 02 41
97 33 33 41 99 5C 29 41 90 3D 71 41 91 D7 0A 47
0F C6 14 00 00 01 16 6A E0 68 80 41 93 B4 05 41
97 1E B8 41 90 7A E1 41 96 8F 57 46 E6 2E 80 00
00 01 16 7A 53 7C 80 FF FF

其结构是：

DATA, TYPE, DESCRIPTION

00 00 00 01, 4 bytes, Symbol Count =1

00 04, 2 bytes, Symbol Length = 4

41 4D 54 44, 6 bytes, Symbol = AMTD

00, 1 byte, Error code = 0 (OK)

00 00 00 02, 4 bytes, Bar Count =  2

FIRST BAR

41 97 33 33, 4 bytes, Close = 18.90

41 99 5C 29, 4 bytes, High = 19.17

41 90 3D 71, 4 bytes, Low = 18.03

41 91 D7 0A, 4 bytes, Open = 18.23

47 0F C6 14, 4 bytes, Volume = 3,680,608

00 00 01 16 6A E0 68 80, 8 bytes, Timestamp = November 23,2007

SECOND BAR

41 93 B4 05, 4 bytes, Close = 18.4629

41 97 1E B8, 4 bytes, High = 18.89

41 90 7A E1, 4 bytes, Low = 18.06

41 96 8F 57, 4 bytes, Open = 18.82

46 E6 2E 80, 4 bytes, Volume = 2,946,325

00 00 01 16 7A 53 7C 80, 8 bytes, Timestamp = November 26,2007

TERMINATOR

FF FF, 2 bytes,

如何读取这样的二进制数据？

提前致谢。

更新：

我用前面的代码在前6个字节上尝试了struct module：

struct.unpack('ih', response.read(6))

（16777216,1024）

但它应该输出（1,4）。 我看一下手册，但不知道出了什么问题。

Answer 1

所以这是我最好的解释你给出的数据......：

import datetime
import struct

class Printable(object):
  specials = ()
  def __str__(self):
    resultlines = []
    for pair in self.__dict__.items():
      if pair[0] in self.specials: continue
      resultlines.append('%10s %s' % pair)
    return '\n'.join(resultlines)

head_fmt = '>IH6sBH'
head_struct = struct.Struct(head_fmt)
class Header(Printable):
  specials = ('bars',)
  def __init__(self, symbol_count, symbol_length,
               symbol, error_code, bar_count):
    self.__dict__.update(locals())
    self.bars = []
    del self.self

bar_fmt = '>5fQ'
bar_struct = struct.Struct(bar_fmt)
class Bar(Printable):
  specials = ('header',)
  def __init__(self, header, close, high, low,
               open, volume, timestamp):
    self.__dict__.update(locals())
    self.header.bars.append(self)
    del self.self
    self.timestamp /= 1000.0
    self.timestamp = datetime.date.fromtimestamp(self.timestamp)

def showdata(data):
  terminator = '\xff' * 2
  assert data[-2:] == terminator
  head_data = head_struct.unpack(data[:head_struct.size])
  try:
    assert head_data[4] * bar_struct.size + head_struct.size == \
           len(data) - len(terminator)
  except AssertionError:
    print 'data length is %d' % len(data)
    print 'head struct size is %d' % head_struct.size
    print 'bar struct size is %d' % bar_struct.size
    print 'number of bars is %d' % head_data[4]
    print 'head data:', head_data
    print 'terminator:', terminator
    print 'so, something is wrong, since',
    print head_data[4] * bar_struct.size + head_struct.size, '!=',
    print len(data) - len(terminator)
    raise

  head = Header(*head_data)
  for i in range(head.bar_count):
    bar_substr = data[head_struct.size + i * bar_struct.size:
                      head_struct.size + (i+1) * bar_struct.size]
    bar_data = bar_struct.unpack(bar_substr)
    Bar(head, *bar_data)
  assert len(head.bars) == head.bar_count
  print head
  for i, x in enumerate(head.bars):
    print 'Bar #%s' % i
    print x

datas = '''
00 00 00 01 00 04 41 4D 54 44 00 00 00 00 02 41
97 33 33 41 99 5C 29 41 90 3D 71 41 91 D7 0A 47
0F C6 14 00 00 01 16 6A E0 68 80 41 93 B4 05 41
97 1E B8 41 90 7A E1 41 96 8F 57 46 E6 2E 80 00
00 01 16 7A 53 7C 80 FF FF
'''

data = ''.join(chr(int(x, 16)) for x in datas.split())
showdata(data)

这会发出：

symbol_count 1
 bar_count 2
    symbol AMTD
error_code 0
symbol_length 4
Bar #0
    volume 36806.078125
 timestamp 2007-11-22
      high 19.1700000763
       low 18.0300006866
     close 18.8999996185
      open 18.2299995422
Bar #1
    volume 29463.25
 timestamp 2007-11-25
      high 18.8899993896
       low 18.0599994659
     close 18.4629001617
      open 18.8199901581

...看起来非常接近你想要的东西，除了一些输出格式细节。 希望这可以帮助！-）

Answer 2

>>> data
'\x00\x00\x00\x01\x00\x04AMTD\x00\x00\x00\x00\x02A\x9733A\x99\\)A\x90=qA\x91\xd7\nG\x0f\xc6\x14\x00\x00\x01\x16j\xe0h\x80A\x93\xb4\x05A\x97\x1e\xb8A\x90z\xe1A\x96\x8fWF\xe6.\x80\x00\x00\x01\x16zS|\x80\xff\xff'
>>> from struct import unpack, calcsize
>>> scount, slength = unpack("!IH", data[:6])
>>> assert scount == 1
>>> symbol, error_code = unpack("!%dsb" % slength, data[6:6+slength+1])
>>> assert error_code == 0
>>> symbol
'AMTD'
>>> bar_count = unpack("!I", data[6+slength+1:6+slength+1+4])
>>> bar_count
(2,)
>>> bar_format = "!5fQ"                                                         
>>> from collections import namedtuple
>>> Bar = namedtuple("Bar", "Close High Low Open Volume Timestamp")             
>>> b = Bar(*unpack(bar_format, data[6+slength+1+4:6+slength+1+4+calcsize(bar_format)]))
>>> b
Bar(Close=18.899999618530273, High=19.170000076293945, Low=18.030000686645508, Open=18.229999542236328, Volume=36806.078125, Timestamp=1195794000000L)
>>> import time
>>> time.ctime(b.Timestamp//1000)
'Fri Nov 23 08:00:00 2007'
>>> int(b.Volume*100 + 0.5)
3680608

Answer 3

 >>> struct.unpack('ih', response.read(6)) (16777216, 1024) 

您正在小端机器上解压缩大端数据。 试试这个：

>>> struct.unpack('!IH', response.read(6))
(1L, 4)

这告诉unpack考虑网络顺序（big-endian）中的数据。 此外，计数和长度的值不能为负数，因此您应该在格式字符串中使用无符号变量。

Answer 4

看一下struct模块中的struct.unpack 。

Answer 5

使用“struct”包中的pack / unpack函数。 更多信息请访问http://docs.python.org/library/struct.html

再见！

Answer 6

正如已经提到的， struct是您需要使用的模块。

请阅读其文档以了解字节顺序等。

在您的示例中，您需要执行以下操作（因为您的数据是big-endian和unsigned）：

>>> import struct
>>> x = '\x00\x00\x00\x01\x00\x04'
>>> struct.unpack('>IH', x)
(1, 4)