# 定义一个学生类，用来形容学生# 定义一个空的类
class Student():pass# 定义一个对象
Jason = Student()# 定义一个类，用来描述听Python的学生
class PythonStudent():name = Noneage = 18course = "Python"# 需要注意# 1. def doHomework的缩进层级# 2. 系统默认有一个self参数def doHomework(self):print("Doing homework")return None# 实例化一个叫liu的学生，是一个具体的人
liu = PythonStudent()
print(liu.name)# 注意成员函数的调用没有传递进入参数
liu.doHomework()
None
Doing homework
# 类变量，不属于具体的某个对象，属于A类的
class A():name = "jason"age = 18A.__dict__a = A()
print(a.name)
jason

class A():name = "jason"age = 18def say(self):self.name = "aaa"self.age = 200# 类对象的属性和实例对象的实例的属性在不对对象的实例属性赋值的前提下，执行同一个变量# A称为类实例
print(A.name)
print(A.age)print("*" * 20)print(id(A.name))
print(id(A.age))print("*" * 20)a = A()
print(a.name)
print(a.age)
print(id(a.name))
print(id(a.age))
jason
18
********************
4563031520
4526644384
********************
jason
18
4563031520
4526644384
class A():name = "jason"age = 18def say(self):self.name = "aaa"self.age = 200def __init__(self, name):self.name = nameprint(id(A.name))a = A("tony9")
print(id(a.name))
a.name = "tony"
print(id(a.name))
4427228696
4427229872
4427228472
# A称为类实例
print(A.name)
print(A.age)print("*" * 20)print(id(A.name))
print(id(A.age))print("*" * 20)
a = A()print(A.__dict__)
print(a.__dict__)a.name = "liu"
a.age = 16print(a.__dict__)print(a.name)
print(a.age)
print(id(a.name))
print(id(a.age))
jason
18
********************
4563031520
4526644384
********************
{'__module__': '__main__', 'name': 'jason', 'age': 18, 'say': <function A.say at 0x10ffb2620>, '__dict__': <attribute '__dict__' of 'A' objects>, '__weakref__': <attribute '__weakref__' of 'A' objects>, '__doc__': None}
{}
{'name': 'liu', 'age': 16}
liu
16
4563032192
4526644320

# 类方法案例1
from time import time, localtime, sleepclass Clock(object):def __init__(self, hour=0, minute=0, second=0):self._hour = hourself._minute = minuteself._second = second@classmethoddef now(cls):ctime = localtime(time())return cls(ctime.tm_hour, ctime.tm_min, ctime.tm_sec)def run(self):self._second += 1if self._second == 60:self._second = 0self._minute += 1if self._minute == 60:self._minute = 0self._hour += 1if self._hour == 24:self._hour = 0def show(self):"""显示时间"""return '%02d:%02d:%02d' % (self._hour, self._minute, self._second)def main():# 通过类方法创建对象并获取系统时间clock = Clock.now()while True:print(clock.show())sleep(1)clock.run()if __name__ == '__main__':main()
08:59:38
08:59:39
08:59:40
08:59:41
08:59:42
08:59:43
08:59:44
08:59:45
08:59:46
08:59:47
08:59:48
08:59:49

# self案例，self并不是关键字
class Student():name = "jason"age = 18def say(self):self.name = "aaa"self.age = 200print("My name is {0}".format(self.name))print("My age is {0}".format(self.age))def sayagain(s):print("My name is {0}".format(s.name))print("My age is {0}".format(s.age))
stu = Student()
stu.say()
stu.sayagain()
My name is aaa
My age is 200
My name is aaa
My age is 200
# 案例class Student():name = "jason"age = 18def say(self):self.name = "aaa"self.age = 200print("My name is {0}".format(self.name))print("My age is {0}".format(self.age))print("class age is {0}".format(__class__.age))def sayagain():print(__class__.name)print(__class__.age)print("hello")stu = Student()
stu.say()
stu.sayagain()
Student.sayagain()
My name is aaa
My age is 200
class age is 18---------------------------------------------------------------------------TypeError                                 Traceback (most recent call last)<ipython-input-4-e1a607ea9759> in <module>19 stu = Student()20 stu.say()
---> 21 stu.sayagain()22 Student.sayagain()TypeError: sayagain() takes 0 positional arguments but 1 was given
# 关于self的案例，以下代码，利用了鸭子模型class A():name = "jasonliu"age = 18def __init__(self):self.name = "tonyliu"self.age = 200def say(self):print(self.name)print(self.age)class B():name = "bbb"age = 90a = A()
# 此时，系统会默认把a作为第一个参数传入函数
a.say()# 此时，self被a替换
A.say(a)# 同样可以把A作为参数传入
A.say(A)# 此时，传入的是类实例B，因为B具有name和age属性，所以不会报错
A.say(B)
tonyliu
200
tonyliu
200
jasonliu
18
bbb
90

# 封装案例1，实例属性
class Student():def __init__(self, name):self.__name = nameself._age = 18def get_name(self):print("My name is {0}".format(self.__name))class low_student(Student):def get_age(self):print("My age is {0}".format(self._age))liu = Student("liucheng")
#print(liu.name)
print(liu._Student__name)
#print(liu.age)
print(liu._age)
liu.get_name()
han = low_student("liuxiang")
han.get_age()
liucheng
18
My name is liucheng
My age is 18
# 封装案例2，类属性
class Student1():name = "jason"__age = 18_schole = "shanghai"def get_age(self):print("My name is {0}".format(self.__age))s = Student1()
print(s.name)print(s._Student1__age)
print(s._schole)
s._schole = "beijing"
print(s._schole)
print(Student1._schole)
s.name = "tony"
print(s.name)
print(Student1.name)
jason
18
shanghai
beijing
shanghai
tony
jason

# 继承语法
# 在Python中，任何类都有一个共同的父类叫objectclass Person():name = "NoName"age = 0__score = 0 # 考试成绩是秘密，只要自己知道_petname = "sec" #小名，是保护的，子类可以用，但不能公用def sleep(self):print("sleeping ...")# 父类写在括号内
class Teacher(Person):teacher_id = "9527"def make_test(self):print("attention")t = Teacher()
print(t.name)
print(Teacher.name)print(t._petname)# 公开访问私有变量会报错
#print(t.__score)t.sleep()
print(t.teacher_id)
t.make_test()
NoName
NoName
sec
sleeping ...
9527
attention
# 子类扩充父类的方法
class Person():name = "NoName"age = 0__score = 0 # 考试成绩是秘密，只要自己知道_petname = "sec" #小名，是保护的，子类可以用，但不能公用def sleep(self):print("sleeping ...")def work(self):print("make some money")# 父类写在括号内
class Teacher(Person):teacher_id = "9527"def make_test(self):print("attention")def work(self):#Person.work(self)super().work()self.make_test()t = Teacher()
t.work()
make some money
attention
class SchoolMember:def __init__(self, name, age):self.name = nameself.age = agedef tell(self):# 打印个人信息print('Name:"{}" Age:"{}"'.format(self.name, self.age), end=" ")class Teacher(SchoolMember):def __init__(self, name, age, salary):SchoolMember.__init__(self, name, age) # 利用父类进行初始化self.salary = salary# 方法重写def tell(self):SchoolMember.tell(self)  # super().tell() print('Salary: {}'.format(self.salary))

class Dog():# 每次实例化的时候，第一个被调用# 因为主要工作是进行初始化，所以得名def __init__(self):print("I am init in dog")kaka = Dog()
I am init in dog
# 继承中的构造函数 -1
class Animal():passclass PaxingAni(Animal):passclass Dog(PaxingAni):def __init__(self):print("I am init in dog")# 实例化的时候，括号内的参数需要跟构造函数参数匹配
kaka = Dog()
I am init in dog
# 继承中的构造函数 -2
class Animal():passclass PaxingAni(Animal):def __init__(self):print("Paxing dongwu")class Dog(PaxingAni):def __init__(self):print("I am init in dog")# 实例化的时候，括号内的参数需要跟构造函数参数匹配
# 因为找到了构造函数，则不再查找父类的构造函数
kaka = Dog()class Cat(PaxingAni):pass# 此时应该自动调用构造函数，因为Cat没有构造函数，所以查找父类的构造函数
# 在PaxinAni中查找到了
c = Cat()
I am init in dog
Paxing dongwu
# 继承中的构造函数 -3
class Animal():def __init__(self):print("Animal")class PaxingAni(Animal):def __init__(self, name):print("Paxing dongwu {0}".format(name))class Dog(PaxingAni):def __init__(self):print("I am init in dog")# 实例化Dog时，查找到Dog的构造函数，参数匹配，不报错
d = Dog()class Cat(PaxingAni):pass# 此时，由于Cat没有构造函数，则向上查找
# 因为PaxingAni的构造函数需要两个参数，实例化的时候给了一个，报错
c = Cat()
I am init in dog---------------------------------------------------------------------------TypeError                                 Traceback (most recent call last)<ipython-input-51-7ccb365305f0> in <module>20 # 此时，由于Cat没有构造函数，则向上查找21 # 因为PaxingAni的构造函数需要两个参数，实例化的时候给了一个，报错
---> 22 c = Cat()TypeError: __init__() missing 1 required positional argument: 'name'
# 继承中的构造函数 -4
class Animal():def __init__(self):print("Animal")class PaxingAni(Animal):passclass Dog(PaxingAni):passd = Dog()class Cat(PaxingAni):passc = Cat()
Animal
Animal

class A():passclass B(A):passclass C(B, A):passprint(A.__mro__)
print(B.__mro__)
(<class '__main__.A'>, <class 'object'>)
(<class '__main__.B'>, <class '__main__.A'>, <class 'object'>)

# 多继承的例子
# 子类可以直接拥有父类的属性和方法，私有属性和方法除外
class Fish():def __init__(self, name):self.name = namedef swim(self):print("i am swimming....")class Bird():def __init__(self, name):self.name = namedef fly(self):print("i am flying....")class Person():def __init__(self, name):self.name = namedef workd(self):print("Working.......")class SuperMan(Person, Bird, Fish):def __init__(self, name):self.name = names = SuperMan("jason")
s.fly()
s.swim()# 单继承的例子
class Student(Person):def __init__(self, name):self.name = namestu = Student('jason')
stu.workd()
i am flying....
i am swimming....
Working.......
# 菱形继承问题
class A():passclass B(A):passclass C(A):passclass D(B, C):pass
# Mixin案例
class Vehicle(object):passclass PlaneMixin(object):def fly(self):print('I am flying')class Airplane(Vehicle, PlaneMixin):pass
class Displayer():def display(self, message):print(message)class LoggerMixin():def log(self, message, filename='logfile.txt'):with open(filename, 'a') as fh:fh.write(message)def display(self, message):super().display(message)self.log(message)class MySubClass(LoggerMixin, Displayer):def log(self, message):super().log(message, filename='subclasslog.txt')subclass = MySubClass()
print(MySubClass.__mro__)
#subclass.display("This string will be shown and logged in subclasslog.txt")
(<class '__main__.MySubClass'>, <class '__main__.LoggerMixin'>, <class '__main__.Displayer'>, <class 'object'>)

# 多态案例
from abc import ABCMeta, abstractmethodclass Pet(object, metaclass=ABCMeta):"""宠物"""def __init__(self, nickname):self._nickname = nickname@abstractmethoddef make_voice(self):"""发出声音"""passclass Dog(Pet):"""狗"""def make_voice(self):print('%s: 汪汪汪...' % self._nickname)class Cat(Pet):"""猫"""def make_voice(self):print('%s: 喵...喵...' % self._nickname)def main():pets = [Dog('旺财'), Cat('凯蒂'), Dog('大黄')]for pet in pets:pet.make_voice()if __name__ == '__main__':main()
旺财: 汪汪汪...
凯蒂: 喵...喵...
大黄: 汪汪汪...

- 检测一个类是否是一个类的子类- issubclass
- 检测一个对象是否是对象实例- isinstance
- 检测一个对象是否有成员xxx- hasattr- getattr- setattr- delattr

- __dict__：以字典的方式显示类的成员组成
- __doct__：获取类的文档属性
- __name__：获取类的名称，如果在模块中使用，获取模块的名称
- __bases__：获取类的所有父类，以元组的形式展现

# 创建Student类，描述学生类，学生具有Student.name属性，但name格式并不统一
class Student():def __init__(self, name, age):self.name = nameself.age = ageself.setName(name)def intro(self):print("hi, my name is {0}".format(self.name))# 方法1 增加setName方法def setName(self, name):self.name = name.upper()s1 = Student("LIU Jason", 19)
s2 = Student("tony liu", 20)
s1.intro()
s2.intro()
hi, my name is LIU JASON
hi, my name is TONY LIU
# property函数案例
# 定义一个Person类，具有name, age属性
# 对于任意输入的姓名，我们希望都用大写方式保存
# 年龄，我们希望内部统一用整数保存class Person():def fget(self):return self._name * 2def fset(self, name):self._name = name.upper()def fdel(self):self._name = "NoName"name = property(fget, fset, fdel, "对name进行操作")p1 = Person()
p1.name = "test"
print(p1.name)
TESTTEST
# 将 property 函数用作装饰器class Person():def __init__(self):self._name = None@propertydef name(self):return self._name@name.setterdef name(self, name):self._name = name@name.deleterdef name(self):del self._namep2 = Person()
#p2.name = "jason"
print(p2.name)
None
# 类方法案例1
from time import time, localtime, sleepclass Clock(object):def __init__(self, hour=0, minute=0, second=0):self._hour = hourself._minute = minuteself._second = second@classmethoddef now(cls):ctime = localtime(time())return cls(ctime.tm_hour, ctime.tm_min, ctime.tm_sec)def run(self):self._second += 1if self._second == 60:

# 静态方法案例1
from math import sqrtclass Triangle(object):def __init__(self, a, b, c):self._a = aself._b = bself._c = c@staticmethoddef is_valid(a, b, c):return a + b > c and b + c > a and a + c > bdef perimeter(self):return self._a + self._b + self._cdef area(self):half = self.perimeter() / 2return sqrt(half * (half - self._a) *(half - self._b) * (half - self._c))if __name__ == "__main__":a, b, c = 3, 4, 5if Triangle.is_valid(a, b, c):t = Triangle(a, b, c)print(t.perimeter())print(t.area())else:print('无法构成三角形.')
12
6.0
# 自定义静态方法案例2
from math import sqrtclass myStaticObject(object):def __init__(self, fun):self.fun = fundef __get__(self, instance, owner):print('call myStaticObject __get__')return self.fundef my_static_method(fun):return myStaticObject(fun)class Triangle(object):def __init__(self, a, b, c):self._a = aself._b = bself._c = c@my_static_methoddef is_valid(a, b, c):return a + b > c and b + c > a and a + c > bdef perimeter(self):return self._a + self._b + self._cdef area(self):half = self.perimeter() / 2return sqrt(half * (half - self._a) *(half - self._b) * (half - self._c))if __name__ == "__main__":a, b, c = 3, 4, 5if Triangle.is_valid(a, b, c):t = Triangle(a, b, c)print(t.perimeter())print(t.area())else:print('无法构成三角形.')
call myStaticObject __get__
12
6.0
# 类方法案例1
from time import time, localtime, sleepclass Clock(object):def __init__(self, hour=0, minute=0, second=0):self._hour = hourself._minute = minuteself._second = second@classmethoddef now(cls):ctime = localtime(time())return cls(ctime.tm_hour, ctime.tm_min, ctime.tm_sec)def run(self):self._second += 1if self._second == 60:
File "<ipython-input-55-4d7c40e59cb2>", line 17if self._second == 60:^
SyntaxError: unexpected EOF while parsing