Use Python struct

Python struct module

The main content from: http://blog.163.com/sywxf@126/blog/static/50671196201011319507710/

 

Simply read a binary file:

 

# 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')

 

This file stores a struct

Struct ABC {

Int;

Float B;

Double C;

Short D;

};

 

The C ++ code is:

// Writeandreadbin. cpp: defines the entry point of the console application.

//

#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 is used to read some simple structure files. The following binary files are read and related field values are displayed:

#!usr/bin/env python

# coding: utf-8

# read_codefilelist.py

'''

typedef struct SecuCodeNewFileItem

{

Unsigned int secucode; // securities code

Unsigned char secuname [20]; // securities name,

Unsigned int markettype; // New Market Type

    signed char        Jianpin[8];

Float pervclose; // collect

Float last5av; // average volume per minute in the past 5 days, used for computing Ratio

Float circulation; // circulation Disk

}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")

 

Later, I thought about it. The previous writing method is still a little troublesome. The purpose of using python is to speed up. The previous writing method is inconvenient when the structure needs to be changed. The following is faster:

#!usr/bin/env python

# coding: utf-8

# read_codefilelist.py

'''

typedef struct SecuCodeNewFileItem

{

Unsigned int secucode; // securities code

Unsigned char secuname [20]; // securities name,

Unsigned int markettype; // New Market Type

    signed char        Jianpin[8];

Float pervclose; // collect

Float last5av; // average volume per minute in the past 5 days, used for computing Ratio

Float circulation; // circulation Disk

}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")