python——面向对象

一、面向过程，是按照问题解决步骤，一步一步的进行，思路比较简单，但是不易维护，面向对象编程是将问题分块，各个模块搭建最后的总的解决方案

1、铅球问题的面向对象编程

from math import sin, cos, radians
 #创建类
class Projectile:
    def __init__(self, angle, velocity, height):
        
        #创建状态，根据给定的发射角度、初始速度和位置创建一个投射体对象
        self.xpos = 0.0
        self.ypos = height
        theta = radians(angle)
        self.xvel = velocity * cos(theta)
        self.yvel = velocity * sin(theta)

    #创建类的方法
    def update(self, time):
        #更新投射体的状态
        self.xpos = self.xpos + time * self.xvel
        yvell = self.yvel - 9.8 * time
        self.ypos = self.ypos + time * (self.yvel + yvell) / 2.0
        self.yvel = yvell
 
    def getY(self):
        #返回投射体的角度
        return self.ypos
 
    def getX(self):
        #返回投射体的距离
        return self.xpos

调用类

from Projectile import *
 
def getInputs():
    a = eval(input("Enter the launch angle (in degrees):"))
    v = eval(input("Enter the initial velocity (in meters/sec):"))
    h = eval(input("Enter the initial height (in meters):"))
    t = eval(input("Enter the time interval: "))
    return a,v,h,t
 
def main():
    angle,vel,h0,time = getInputs()#输入参数
    shot = Projectile(angle,vel,h0)#调用类，注意只用三个参数
    while shot.getY() >=0:
        shot.update(time)
    print("
Distance traveled:{0:0.1f}meters.".format(shot.getX()))
   
if __name__ == "__main__":
    main()

2、GPA

# 找到GPA最高的学生

 #定义类
class Student:
    def __init__(self, name, hours, qpoints):
        self.name = name
        self.hours = float(hours)
        self.qpoints = float(qpoints)
        
    #定义方法 
    def getName(self):
        return self.name
     
    def getHours(self):
        return self.hours
     
    def getQPoints(self):
        return self.qpoints
     
    def gpa(self):
        return self.qpoints/self.hours

#定义函数，获取每一行数据   
def makeStudent(infoStr):
    name, hours, qpoints = infoStr.split("	")
    return Student(name, hours, qpoints)
     
def main():
    # 打开输入文件
    filename = input("Enter name the grade file: ")
    infile = open(filename, 'r')
    # 设置文件中第一个学生的记录为best
    best = makeStudent(infile.readline())
 
    # 处理文件剩余行数据
    for line in infile:
        # 将每一行数据转换为一个记录
        s = makeStudent(line)
        # 如果该学生是目前GPA最高的，则记录下来
        if s.gpa() > best.gpa():
            best = s
    infile.close()
 
    # 打印GPA成绩最高的学生信息
    print("The best student is:", best.getName())
    print("hours:", best.getHours())
    print("GPA:", best.gpa())
 
if __name__ == '__main__':
    main()