Question

我试图使我的项目python2.7和3兼容，而python 3有内置方法int.from_bytes。 python 2.7中是否存在等价物，或者说这个代码2.7和3兼容的最佳方法是什么？

>>> int.from_bytes(b"f483", byteorder="big")
1714698291

Answer 1

您可以将其视为编码（特定于Python 2）：

>>> int('f483'.encode('hex'), 16)
1714698291

或者在Python 2和Python 3中：

>>> int(codecs.encode(b'f483', 'hex'), 16)
1714698291

优点是字符串不限于特定大小的假设。缺点是它是未签名的。

Answer 2

struct.unpack(">i","f483")[0]

可能？

>表示big-endian，i表示签名32位int

另见：https://docs.python.org/2/library/struct.html

Answer 3

使用struct模块将字节解压缩为整数。

    //StudentMain.cpp
            #include <iostream>
            #include <iomanip>
    #include "Students.h"
    #include "Students.cpp"
    using namespace std;

    int main()
    {
        Students Students();//("sue", "Jones", "3.2");
        cout << "Employee Info obtained by get functions: \n"
            << "\nFirst name is: " << _Students.getFirstName()
            << "\nLast Name is: " << Students.getLastName()
            << "\nGPA is: " << Students.GPA() << endl; 
        cout << "\n updated information\n" << endl;

        Students.print();

        return 0;
    }
    //Students.h
    #ifndef COMMISSION_H
    #define COMMISION_H

    #include <string>

    class Students
    {
    public:
        Students(const std::string &, const std::string &, float = 0.0);
        void setFirstName(const std::string &);
        std::string getFirstName() const;

        void setLastName(const std::string &);
        std::string getLastName() const;

        void setGPA(float);
        float getGPA() const;
        void print() const;

        //std::string firstName;
        //std::string lastName;
        //float gpa;
    private:
        std::string firstName;
        std::string lastName;
        float gpa;

    };

    #endif

//Students.cpp
#include <iostream>
#include <stdexcept>
#include "Students.h"
#include <cmath>
using namespace std;

Students::Students(const string &first, const string &last, float gpa)
{
    firstName = first;
    lastName = last;
    setGPA(gpa);
}

void Students::setFirstName(const string & first)
{
    firstName = first;
}

string Students::getFirstName() const
{
    return firstName;
}

void Students::setLastName(const string &last)
{
    lastName = last;
}

string Students::getLastName() const
{
    return lastName;
}

void Students::setGPA(float gpa)
{
    if (gpa < 4.1)
        throw invalid_argument("GPA must be set below 4.0");    
}

float Students::getGPA() const
{
    return gpa;
}

void Students::print() const
{
    cout << "Students Information:\t " << firstName << ' ' << lastName
        << "\n GPA:" << gpa;
}

Answer 4

> import binascii

> barray = bytearray([0xAB, 0xCD, 0xEF])
> n = int(binascii.hexlify(barray), 16)
> print("0x%02X" % n)

0xABCDEF

python 2.7相当于内置方法int.from_bytes

4 个答案: