python struct使用

简单读一个二进制文件:

# coding: utf-8

import struct

import sys

binfile=open('test.bin','rb')

buf = binfile.read()

unpackIndex = 0

a,b,c,d = struct.unpack_from('ifdh', buf, unpackIndex)

print a, b, c, d

unpackIndex += struct.calcsize('ifdh')

此文件存储一个结构体

struct abc{

int a;

float b;

double c;

short d;

};

c++代码为:

// writeandreadbin.cpp : 定义控制台应用程序的入口点。

//

#include "stdafx.h"

#include<fstream>

#include <iostream>

using namespace std;

void main()

    ofstream fwrite("test.bin", ios::out | ios::app | ios::binary);

    if(!fwrite){

        cout<<"File open error!\n";

        return;

    int a = 0x12345678;

    float b = 3.25;

    double c = 4.33;

    short d = 0x2468;

    fwrite.write((char*)&a, sizeof(a));

    fwrite.write((char*)&b, sizeof(b));

    fwrite.write((char*)&c, sizeof(c));

    fwrite.write((char*)&d, sizeof(d));

    fwrite.close();

    ifstream fread("test.bin", ios::in|ios::binary);

    if(!fread)

        cout<<"File open error!"<<endl;

        return;

    fread.read((char*)&a, sizeof(a));

    fread.read((char*)&b, sizeof(b));

    fread.read((char*)&c, sizeof(c));

    fread.read((char*)&d, sizeof(d));

    fread.close();

    cout<<a<<endl;

    cout<<b<<endl;

    cout<<c<<endl;

    cout<<d<<endl;

python用以做一些简单的结构文件的读取还是很不错的,如下读取的二进制文件,显示出相关字段值:

#!usr/bin/env python

# coding: utf-8

# read_codefilelist.py

'''

typedef struct SecuCodeNewFileItem

    unsigned int    SecuCode;       // 证券代码

    unsigned char    SecuName[20];   // 证券名称,

    unsigned int    MarketType;     // 新市场类型

    signed char        Jianpin[8];

    float            PervClose;      // 昨收

    float            Last5AV;        // 过去5日平均每分钟成交量,用于计算量比

    float            Circulation;    // 流通盘

}structSecuCodeNewFileItem;

'''

import struct

import sys

type = sys.getfilesystemencoding()

binfile=open('codelist_pad.dat','rb')

buf = binfile.read()

unpackIndex = 0

count = struct.unpack_from('i', buf, unpackIndex)

unpackIndex += struct.calcsize('i')

print 'count=', count[0]

for i in range(0, count[0], 1):

    SecuCode,\

    SecuName,    \

    MarketType,  \

    Jianpin, \

    PervClose, \

    Last5AV, \

    Circulation = struct.unpack_from('i20si8sfff', buf, unpackIndex)

    print '%06d'%SecuCode, MarketType, \

          SecuName.decode(encoding='UTF-8', errors='ignore').rstrip('\000')

    unpackIndex += struct.calcsize('i20si8sfff')

name = input("Please input any key to exit:\n")

后来想了一下,前面的写法还是有点麻烦,用python目的就是为了快,前面的写法在需要改结构的时候,显得很不方便,以下更快一点:

#!usr/bin/env python

# coding: utf-8

# read_codefilelist.py

'''

typedef struct SecuCodeNewFileItem

    unsigned int    SecuCode;       // 证券代码

    unsigned char    SecuName[20];   // 证券名称,

    unsigned int    MarketType;     // 新市场类型

    signed char        Jianpin[8];

    float            PervClose;      // 昨收

    float            Last5AV;        // 过去5日平均每分钟成交量,用于计算量比

    float            Circulation;    // 流通盘

}structSecuCodeNewFileItem;

'''

import struct

import sys

type = sys.getfilesystemencoding()

binfile=open('codelist_pad.dat','rb')

buf = binfile.read()

unpackIndex = 0

count = struct.unpack_from('i', buf, unpackIndex)

unpackIndex += struct.calcsize('i')

print 'count=', count[0]

for i in range(0, count[0], 1):

    data = struct.unpack_from('i20si8sfff', buf, unpackIndex)

    print '%06d'%data[0], data[2],\

          data[1].decode(encoding='UTF-8', errors='ignore').rstrip('\000')

    unpackIndex += struct.calcsize('i20si8sfff')

name = input("Please input any key to exit:\n")