比较:4字节bytearray转化为int

Jacky <[email protected]>
to      "python-cn`CPyUG`华蟒用户组(中文Py用户组)" <[email protected]>
cc      [email protected],
[email protected]
date    Mon, Aug 16, 2010 at 22:10
subject 方案比较：快速将4字节bytearray转化为int

代码

{{{#1python

import struct import ctypes

def test_struct(buf, offset):

• return struct.unpack_from("I", buf, offset)[0]

def test_ctypes(buf, offset):

• return ctypes.c_uint32.from_buffer(buf, offset).value

def test_multi(buf, offset):

• return buf[offset] + (buf[offset+1] << 8) + (buf[offset+2] << 16) +(buf[offset+3] << 24)

buf_w = bytearray(5) buf_w[1] = 1 buf_r = buffer(buf_w)

if name == 'main':

• import timeit t1 = timeit.Timer("test_struct(buf_r, 1)",

  • "from main import test_struct, buf_r")

  t2 = timeit.Timer("test_ctypes(buf_w, 1)",

  • "from main import test_ctypes, buf_w")

  t3 = timeit.Timer("test_multi(buf_w, 1)",

  • "from main import test_multi, buf_w")

  print t1.timeit(number=1000) print t2.timeit(number=1000) print t3.timeit(number=1000)

}}}

结果

number = 10000
0.0081958770752
0.012549161911
0.0112121105194

number = 1000
0.00087308883667
0.00125789642334
0.00110197067261

number = 100
0.0000917911529541     # 9.17911529541e-05
0.000133991241455
0.00011420249939

number = 10
1.69277191162e-05
2.19345092773e-05
1.69277191162e-05

number = 1
1.00135803223e-05
1.00135803223e-05
5.96046447754e-06

为什么运行次数不同，结果也有差异呢？

• 测试环境，ubuntu 10.04，我把number调到100w

反馈

创建 by -- ZoomQuiet [2010-08-17 03:44:33]