Python----面向对象---组合

先看一段代码：

class People:
    school = 'luffycity'

    def __int__(self, name, age, sex):
        self.name = name
        self.age = age
        self.sex = sex


class Teacher(People):

    def __init__(self, name, age, sex, level, salary):
        super().__int__(name, age, sex)
        self.level = level
        self.salary = salary

    def teach(self):
        print('%s is teaching' % self.name)


class Student(People):

    def __init__(self, name, age, sex, class_time):
        super().__int__(name, age, sex)
        self.class_time = class_time

    def learn(self):
        print('%s is learning' % self.name)


teacher1 = Teacher('alex', 18, 'male', 10, 3000)
student1 = Student('张三', 28, 'female', '08:30:00')
print(teacher1.__dict__)
print(student1.__dict__)

结果为：

{'name': 'alex', 'age': 18, 'sex': 'male', 'level': 10, 'salary': 3000}
{'name': '张三', 'age': 28, 'sex': 'female', 'class_time': '08:30:00'}

 如果要为，teacher类添加老师所教的课程信息，如课程名，课程价格，课程周期等，可以在init函数里面增加，但是如果多个老师教同一门课程，就会出现代码重复的问题，如下

代码所示：

class People:
    school = 'luffycity'

    def __int__(self, name, age, sex):
        self.name = name
        self.age = age
        self.sex = sex


class Teacher(People):

    def __init__(self, name, age, sex, level, salary, course_name, course_price, cource_period):
        super().__int__(name, age, sex)
        self.level = level
        self.salary = salary
        self.course_name = course_name
        self.course_price = course_price
        self.course_period = cource_period

    def teach(self):
        print('%s is teaching' % self.name)


class Student(People):

    def __init__(self, name, age, sex, class_time):
        super().__int__(name, age, sex)
        self.class_time = class_time

    def learn(self):
        print('%s is learning' % self.name)


teacher1 = Teacher('alex', 18, 'male', 10, 3000, 'python', 3000, '3mons')
teacher2 = Teacher('egon', 28, 'male', 30, 2000, 'python', 3000, '3mons')
student1 = Student('张三', 28, 'female', '08:30:00')
print(teacher1.__dict__)
print(teacher2.__dict__)
print(student1.__dict__)

结果为：

{'name': 'alex', 'age': 18, 'sex': 'male', 'level': 10, 'salary': 3000, 'course_name': 'python', 'course_price': 3000, 'course_period': '3mons'}
{'name': 'egon', 'age': 28, 'sex': 'male', 'level': 30, 'salary': 2000, 'course_name': 'python', 'course_price': 3000, 'course_period': '3mons'}
{'name': '张三', 'age': 28, 'sex': 'female', 'class_time': '08:30:00'}

怎样解决代码重复问题，可以新加一个course类：如下所示：

class Course:
    def __init__(self, course_name, course_price, course_period):
        self.course_name = course_name
        self.course_price = course_price
        self.course_period = course_period

但是，course类和teacher类并没有继承关系，而是一种老师有课程的关系，这样就讲到了组合的用处，就是为了teacher这样的类访问course这样的类的方法，实例如下：

python = Course('python', 3000, '3mons')

teacher1.course = python
teacher2.course = python

print(python)
print(teacher1.course)
print(teacher2.course)

把teacher1的course属性指向一个course实例化对象python，这样执行teacher1.course.就相当于执行python.

结果如下：

<__main__.Course object at 0x000001F01BFC3BA8>
<__main__.Course object at 0x000001F01BFC3BA8>
<__main__.Course object at 0x000001F01BFC3BA8>

为同一块内存地址

print(python.course_name)

print(teacher1.course.course_name)
print(teacher2.course.course_name)

结果为：

python
python
python

 为course添加tell_info 方法，

    def tell_info(self):
        print('课程名<%s> 课程价钱<%s> 课程周期<%s>' % (self.course_name, self.course_price, self.course_period))

teacher1.course.tell_info()的执行结果为：

课程名<python> 课程价钱<3000> 课程周期<3mons>

增加linux实例化对象：

linux = Course('linux', 2000, '4mons')

student1学了两门课程

student1.course1 = python
student1.course2 = linux

查询student1学的课程信息

student1.course1.tell_info()
student1.course2.tell_info()

结果为：

课程名<python> 课程价钱<3000> 课程周期<3mons> 课程名<linux> 课程价钱<2000> 课程周期<4mons>

增加一个Date类：

class Date:
    def __init__(self, year, mon, day):
        self.year = year
        self.mon = mon
        self.day = day

    def tell_info(self):
        print('%s-%s-%s' % (self.year, self.mon, self.day))

实例话一个Date对象d
d = Date(1988, 4, 20)
student1.birth = d
student1.birth.tell_info()
student1.course1.tell_info()

结果为：

1988-4-20
课程名<python> 课程价钱<3000> 课程周期<3mons>