廖雪峰Python学习笔记day6

待我称王封你为后i 2022-12-24 06:58 183阅读 0赞

[学习笔记day5][day5]

# python study day6
    
    # 类属性
    # class Student(object):
    # name = 'Student'
    # s = Student()
    # print(s.name) #>>> Student
    # print(Student.name) #>>> Student
    # s.name = 'newName'
    # print(s.name) #>>> newName
    # del s.name
    # print(s.name) #>>> Student
    # 计算实例数量
    # class Student(object):
    # count = 0
    # def __init__(self, name):
    # self.name = name
    # Student.count +=1
    
    # 实例动态绑定属性
    # s = Student()
    # s.name = 'newName'
    # 实例动态绑定方法
    # def set_age(self, age):
    # self.age = age
    # from types import MethodType
    # s.set_age = MEthodType(set_age, s)
    # 给类class动态方法
    # Student.set_age = set_age
    # 使用__slots__限制动态绑定属性
    # class Student(Object):
    # __slots__ = ('name', 'age') # 用tuple定义允许绑定的属性名称
    # s.socre = 99 # slots没有score >>> AttributeError 
    # 子类未定义slots时不受父类影响，定义后限制是子类+父类
    
    # 内置 @property 可以把一个方法变成属性调用
    # class Student(object):
    # @property
    # def score(self):
    # return self.score
    # @score.setter
    # def sore(self, value):
    # if not isinstance(value, int):
    # raise ValueError('score must be an Integer!')
    # if value < 0 or value > 100:
    # raise ValueError('score must betweeen 0~100!')
    # s = Student()
    # s.score = 60 # 实际转化为s.set_score(60)
    # print(s.score) # 实际转化为s.get_score()
    # 也可以不添加 @score.setter 注解，该属性就是只读属性
    # class Screen(object):
    # @property
    # def width(self):
    # return self._width
    # @width.setter
    # def width(self, width):
    # self._width = width
    # @property
    # def height(self):
    # return self._height
    # @height.setter
    # def height(self, height):
    # self._height = height
    # @property
    # def resolution(self):
    # return self._width*self._height
    # s = Screen()
    # s.width = 1024
    # s.height = 768
    # print('resolution =', s.resolution)
    
    # Python 允许多重继承，类似java接口实现
    # class Dog(Animal, Runnable): 
    # pass
    # 为看出继承关系可以引入MixIn
    # class MyTCPServer(TCPServer, ForkingMixIn):
    # pass # 多进程模式TCP服务
    # class MyUDPServer(UDPServer, ThreadingMixIn):
    # pass # 多线程模式UDP服务
    
    # 定制类
    # class Student(object):
    # pass
    # print(Student()) # 调用__str__()方法，打印实例地址
    # >Student() # 调用__repr__()方法，打印实例地址
    # class Student(object): # 改写打印内容
    # def __init__(self, name):
    # self.name = name
    # def __str__(self):
    # return 'Student object(name=%s)' % self.name
    # __repr__ == __str__
    # __iter__() 方法 list、tuple 类型的 for…in 循环实现
    # __next__() 方法拿到循环下一个值
    # __getitem__() 方法实现list下标获取值，切片，step步长参数，key等
    # __setitem__() 方法对list、dict等集合赋值
    # __delitem__() 方法用于删除元素
    # __getattr__() 方法，在对象调用查找不到属性时调用。如：链式调用
    # class Chain(object):
    # def __init__(self, path=''):
    # self._path = path
    # def __getattr__(self, path):
    # return Chain('%s/%s' % (self._path, path))
    # def __str__(self):
    # return self._path
    # __repr__ = __str__
    # print(Chain().status.user.itemline.list) #>>>/status/user/itemline/list
    # __call__() 方法，定义后可以直接对实例进行调用，执行该方法
    # class Student(object):
    # def __init__(self, name):
    # self._name = name
    # def __call__(self):
    # print('My name is %s.' % self._name)
    # s = Student('Straw')
    # s() #>>> My name is Straw.
    # # 可以通过callable()函数判断类实例是否能被调用
    # callable(max) #>>> True
    # callable('str') #>>> False
    
    # 枚举类，python提供了Enum类
    # from enum import Enum
    # Month = Enum('Month', ('Jan','Feb','Mar','Apr','May',
    # 'Jun','Jul','Aug','Sep','Oct','Nov','Dec'))
    # 从Enum派生出自定义类
    # from enum import Enum, unique
    # @unique # 可以自动检查是否有重复值
    # class Weekday(Enum):
    # Sun = 0
    # Mon = 1
    # Tue = 2
    # Wed = 3
    # Thu = 4
    # Fri = 5
    # Sat = 6
    # print(Weekday.Mon) #>>> Weekday.Mon
    # print(Weekday['Tue']) #>>> weekday.Tue
    # print(Weekday.Tue.value) #>>> 2
    # print(Weekday(1)) #>>> Weekday.Mon
    # for name, per in Weekday.__members__.items():
    # print(name, '==>', per)
    # from enum import Enum
    # class Gender(Enum):
    # Male = 0
    # Female = 1
    # gender = Gender.Male
    # print(isinstance(gender, Gender))
    # class Student(object):
    # def __init__(self, name, gender):
    # self.name = name
    # if isinstance(gender, Gender):
    # self.gender = gender
    # else:
    # raise ValueError('gender value must be Gender Enum!')
    # bart = Student('Bart', 0)
    
    # type() 函数既可以返回一个对象的类型，也可以动态创建一个类
    # def fn(self, name='world'): # 先定义函数
    # print('Hello, %s' % name)
    # Hello = type('Hello', (object,), dict(hello=fn))
    # # 创建Hello class。完成三个参数，1.类名 2.继承的父类集合 3.class方法名函数绑定
    # h = Hello()
    # h.hello() #>>> Hello, world.
    # print(type(Hello)) #>>> <class 'type'>
    # print(type(h)) #>>> <class '__main__.Hello'>
    # 元类 metaclass。一般实例构造过程：先定义metaclass、创建类、最后创建实例
    # metaclass 允许创建类或者修改类，或者可以将类看成由metaclassc创建出来的“实例”

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3plcm9fMTMw_size_16_color_FFFFFF_t_70]  
[学习笔记day7][day7]

[day5]: https://blog.csdn.net/zero_130/article/details/110070187
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3plcm9fMTMw_size_16_color_FFFFFF_t_70]: /images/20221120/0576b7f1c1404b4f8470094abe480f85.png
[day7]: https://blog.csdn.net/zero_130/article/details/110292075