Python----面向对象---组合

先看一段代码：

 1 class People:
 2     school = 'luffycity'
 3 
 4     def __int__(self, name, age, sex):
 5         self.name = name
 6         self.age = age
 7         self.sex = sex
 8 
 9 
10 class Teacher(People):
11 
12     def __init__(self, name, age, sex, level, salary):
13         super().__int__(name, age, sex)
14         self.level = level
15         self.salary = salary
16 
17     def teach(self):
18         print('%s is teaching' % self.name)
19 
20 
21 class Student(People):
22 
23     def __init__(self, name, age, sex, class_time):
24         super().__int__(name, age, sex)
25         self.class_time = class_time
26 
27     def learn(self):
28         print('%s is learning' % self.name)
29 
30 
31 teacher1 = Teacher('alex', 18, 'male', 10, 3000)
32 student1 = Student('张三', 28, 'female', '08:30:00')
33 print(teacher1.__dict__)
34 print(student1.__dict__)
35 
36 结果为：
37 
38 {'name': 'alex', 'age': 18, 'sex': 'male', 'level': 10, 'salary': 3000}
39 {'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：

 1 class People:
 2     school = 'luffycity'
 3 
 4     def __int__(self, name, age, sex):
 5         self.name = name
 6         self.age = age
 7         self.sex = sex
 8 
 9 
10 class Teacher(People):
11 
12     def __init__(self, name, age, sex, level, salary, course_name, course_price, cource_period):
13         super().__int__(name, age, sex)
14         self.level = level
15         self.salary = salary
16         self.course_name = course_name
17         self.course_price = course_price
18         self.course_period = cource_period
19 
20     def teach(self):
21         print('%s is teaching' % self.name)
22 
23 
24 class Student(People):
25 
26     def __init__(self, name, age, sex, class_time):
27         super().__int__(name, age, sex)
28         self.class_time = class_time
29 
30     def learn(self):
31         print('%s is learning' % self.name)
32 
33 
34 teacher1 = Teacher('alex', 18, 'male', 10, 3000, 'python', 3000, '3mons')
35 teacher2 = Teacher('egon', 28, 'male', 30, 2000, 'python', 3000, '3mons')
36 student1 = Student('张三', 28, 'female', '08:30:00')
37 print(teacher1.__dict__)
38 print(teacher2.__dict__)
39 print(student1.__dict__)
40 
41 结果为：
42 
43 {'name': 'alex', 'age': 18, 'sex': 'male', 'level': 10, 'salary': 3000, 'course_name': 'python', 'course_price': 3000, 'course_period': '3mons'}
44 {'name': 'egon', 'age': 28, 'sex': 'male', 'level': 30, 'salary': 2000, 'course_name': 'python', 'course_price': 3000, 'course_period': '3mons'}
45 {'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：

1 class Course:
2     def __init__(self, course_name, course_price, course_period):
3         self.course_name = course_name
4         self.course_price = course_price
5         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：

1 python = Course('python', 3000, '3mons')
2 
3 teacher1.course = python
4 teacher2.course = python
5 
6 print(python)
7 print(teacher1.course)
8 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：

1 <__main__.Course object at 0x000001F01BFC3BA8>
2 <__main__.Course object at 0x000001F01BFC3BA8>
3 <__main__.Course object at 0x000001F01BFC3BA8>
4 
5 为同一块内存地址

 1 print(python.course_name)
 2 
 3 print(teacher1.course.course_name)
 4 print(teacher2.course.course_name)
 5 
 6 结果为：
 7 
 8 python
 9 python
10 python

为course添加tell_info 方法，

1     def tell_info(self):
2         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：

 1 class Date:
 2     def __init__(self, year, mon, day):
 3         self.year = year
 4         self.mon = mon
 5         self.day = day
 6 
 7     def tell_info(self):
 8         print('%s-%s-%s' % (self.year, self.mon, self.day))
 9 
10 实例话一个Date对象d
11 d = Date(1988, 4, 20)
12 student1.birth = d
13 student1.birth.tell_info()
14 student1.course1.tell_info()
15 
16 结果为：

17 1988-4-20
18 课程名<python> 课程价钱<3000> 课程周期<3mons>