Python进阶8---面向对象基础1

面向对象

语言的分类

Python的类

定义

class ClassName:
    pass

class MyCalss:
    """A example class"""#文档字符串
    x = 'abc'#类属性
    
    def foo(self):#类属性foo,也是方法
        return 'myclass'

类对象及类属性

 

实例化

a = MyClass()   #实例化

__init__方法

class MyCalss:

    def __init__(self):#初始化
        print('init')

a  = MyCalss()

实例对象

 

self

class Person:
    def __init__(self):
        print(id(self))

c = Person()    #会调用__init__
print('p={}'.format(id(c)))
#输出结果：
43079160
c=43079160

实例变量和类变量

 

class Person:
    age = 7
    height = 175
    def __init__(self,name,age=23):
        self.name = name
        self.age = age

tom  = Person('tom')
jerry = Person('jerry',20)

Person.age = 30
print(Person.age,tom.age,jerry.age)
print(Person.__dict__,tom.__dict__,jerry.__dict__,sep='
')

Person.height += 5
print(Person.__dict__,tom.__dict__,jerry.__dict__,sep='
')

tom.height = 176
print(Person.__dict__,tom.__dict__,jerry.__dict__,sep='
')

Person.weight = 65
print(Person.__dict__['weight'])
print(tom.__dict__['weight'])#KeyError

装饰一个类

 

#增加类变量
def add_name(name,cls):
    cls.NAME = name #动态增加类属性

#改进成装饰器(带参)
def add_name1(name):
    def wrapper(cls):
        cls.NAME = name
        return cls
    return wrapper

@add_name1('tom')
class Person:
    AGE = 1

print(Person.NAME)

 类方法和静态方法

普通函数

类方法

 

　　

 

静态方法

方法的调用

class Person:
    def normal_method():
        print('nomal')

    def method(self):
        print("{}'s method ".format(self))

    @classmethod
    def class_method(cls):
        print('class = {0.__name__}  {0}'.format(cls))
        cls.HEIGHT  =175

    @staticmethod
    def static_method():
        print(Person.HEIGHT)

#~~~类访问~~~
print(1,Person.normal_method())
# print(2,Person.method())#报错
print(3,Person.class_method())
print(4,Person.static_method())
#~~~实例访问~~~
tom = Person()
# print(5,tom.normal_method())#报错
print(6,tom.method())
print(7,tom.class_method())
print(8,tom.static_method())

 

访问控制

私有属性Private

 

一般来说，可以在内部自定义一个方法来访问私有变量。

私有变量的本质

 

保护变量

 

 

 私有方法

 

 

私有方法的本质

 

私有成员的总结

补丁 

#test1.py
from test2 import Person
from test3 import get_score

def monkeypatch4Person():
    Person.get_score = get_score

print(Person().get_score())
monkeypatch4Person()

print(Person().get_score())

#输出如下：
{'English': 78, 'Chinese': 86, 'History': 82}    #打补丁前
{'name': 'Person', 'English': 88, 'Chinese': 90, 'History': 85}    #打补丁后

#test2.py
class Person:
    def get_score(self):
        ret = {'English':78,'Chinese':86,'History':82}
        return ret

#test3.py
def get_score(self):
    return dict(name=self.__class__.__name__,English=88,Chinese=90,History=85)

属性装饰器

 

class Person:
    def __init__(self,chinese,english,history):
        self._chinese = chinese
        self._eng = english
        self.__his = history

    def gethis(self):
        return self.__his

    def sethis(self,value):
        self.__his = value

    def seteng(self,value):
        self._eng = value

    @property
    def chinese(self):
        return self._chinese

    @chinese.setter
    def chinese(self,value):
        self._chinese = value

    @chinese.deleter
    def chinese(self):
        # del self._chinese
        print('del self._chinese')

    #x = property(getx, setx, delx, "I'm the 'x' property.")
    eng = property(lambda self:self._eng,seteng)

student = Person(80,90,88)
print(student.chinese)#80
student.chinese = 100
print(student.chinese)#100
del student.chinese
print(student.eng)#90
student.eng =110
print(student.eng)#110

对象的销毁

方法重载(overload)

 

重写也就是覆盖的意思，即override。 

封装

练习

 

#1.其结构值得参考！
from random import randint
class RandomGenerator:
    def __init__(self,count=10,start=1,stop=100):
        self.count = count
        self.start = start
        self.stop = stop
        self.gen = self._generatr()

    def _generatr(self):
        while True:
            yield [randint(self.start,self.stop) for _ in range(self.count)]

    def gengerate(self,count):
        self.count = count
        return next(self.gen)

rg = RandomGenerator()
lst = rg.gengerate(10)
print(lst)

#2
class Point:
    def __init__(self,x,y):
        self.x = x
        self.y = y
        
    def __repr__(self):
        return  '{}:{}'.format(self.x,self.y)
lst1 = [Point(*v) for v in zip(rg.gengerate(10),rg.gengerate(10))]
print(lst1)
#输出如下： 
[36:14, 84:20, 31:84, 68:82, 36:48, 87:67, 64:49, 8:15, 55:73, 90:75]

#3
class Car:
    def __init__(self,mark=None,color=None,price=None,speed=None):
        self._mark = mark
        self._color = color
        self._price = price
        self._speed = speed

class CarInfo:
    def __init__(self):
        self.lst = []

    def addcar(self,car:Car):
        self.lst.append(car)

    def showcarinfo(self):
        return self.lst

#4
class Temperature:
    def __init__(self,t,unit='c'):
        self._c = None
        self._f = None
        self._k = None
        if unit == 'k':
            self._c = self.k2c(t)
            self._k = t
        elif unit == 'f':
            self._c = self.f2c(t)
            self._f = t
        else:
            self._c = t

    @property
    def k(self):
        if self._k is None:
            self._k = self.c2k(self._c)
        return self._k

    @property
    def f(self):
        if self._f is None:
            self._f = self.c2f(self._c)
        return self._f

    @property
    def c(self):
        return self._c

    @classmethod
    def c2f(cls,c):
        return c*9/5+32

    @classmethod
    def f2c(cls,f):
        return (f-32)*5/9

    @classmethod
    def c2k(cls,c):
        return c+273.15

    @classmethod
    def k2c(cls,k):
        return k-273.15

    @classmethod
    def f2k(cls,f):
        return cls.c2k(cls.f2c(f))

    @classmethod
    def k2f(cls,k):
        return cls.c2f(cls.k2c(k))

print(Temperature.c2f(40))
print(Temperature.c2k(40))
print(Temperature.f2c(104.0))
print(Temperature.f2k(104.0))
print(Temperature.k2c(313.5))
print(Temperature.k2f(313.5))

t = Temperature(40)
print(t.c,t.f,t.k)

t = Temperature(313.5,'k')
print(t.c,t.f,t.k)

#简单购物车
class Color:
    RED = 0
    BLUE = 1
    GREEN = 2
    BLACK = 3
    GOLDEN = 4
    OTHER = 100

class Item:
    def __init__(self,**kwargs):
        self.__info = kwargs

    def __repr__(self):
        return str(sorted(self.__info.items()))

class Cart:
    def __init__(self):
        self.items = []

    def additem(self,item:Item):
        self.items.append(item)

    def gatallitems(self):
        return self.items

mycart = Cart()
myphone = Item(mark='Iponhe',color=Color.GOLDEN,memory='64G')
mycart.additem(myphone)
mycar = Item(mark='BMW',color=Color.BLACK,memory='220/s')
mycart.additem(mycar)
print(mycart.gatallitems())