Python 【面向对象】

def db_conn():
    print("connecting db...")

def db_backup(dbname):
    print("导出数据库...", dbname)
    print("将备份文件打包，移至相应目录...")

def db_backup_test():
    print("将备份文件导入测试库，看导入是否成功")

def main():
    db_conn()
    db_backup('my_db')
    db_backup_test()

if __name__ == '__main__':
    main()

# 运行结果：
# connecting db...
# 导出数据库... my_db
# 将备份文件打包，移至相应目录...
# 将备份文件导入测试库，看导入是否成功

class Role(object):    #在定义类时继承object就是新式类，没有就是就是旧类式
    public_object = "public"   #在类例定义一个公有属性：所有实例都能访问的属性叫“公有属性”
    def __init__(self,name,role,weapon,life_value=100,money=15000):  #构造函数==初始化方法：模板
        self.name = name    #普通属性
        self.role = role
        self.weapon = weapon
        self.life_value = life_value
        self.money = money
        self.__heart= "Normal"    #私有属性在外面无法访问
    def shot(self):     #类的方法
        print("%s is shooting..."%self.name)
    def got_shot(self):
        print("ah...,I got shot...")
    def buy_gun(self,gun_name):
        print("%s just bought %s" %(self.name,gun_name))
        self.weapon = gun_name          #在购买后让实例值改变

#在下面实例化其实就是传入： Role('r1','Alex','police','AK47') 把r1传给了self
#r1就是实例化后产生的当前Role类的实例，所以self就是实例本身
#我理解r1其实就是__init__函数的内存地址
#所以在下面函数中调用self.name就相当于调用r1.name所以可以调用
r1 = Role('Alex','police','AK47') #生成一个角色  只要一实例化就会自动调用__init__
r2 = Role('Jack','terrorist','B22')  #生成一个角色

r1.shot()
print(r2.weapon)        #在调用r2.buy_gun('AK47')前是：B22
r2.buy_gun('AK47')
print(r2.weapon)        #在调用r2.buy_gun('AK47')后是：AK47

#私有属性
# print(r2.__heart)     #这里的.__heart是私有属性，所以在外部无法访问
print(r2._Role__heart)  #强制访问私有属性的方法

#公有属性
print(r2.public_object) #打印出类的公有属性
Role.public_object = 'change_public'    #从全局改变类的公有属性 r1,r2的公有属性都会变
print(r2.public_object)  #这里打印可以看出公有属性变成类“change_public"
r2.public_object = "public_r2"          #改变r2对象的公有属性，r1不会变
print(r2.public_object)                  #打印出改变后的r2公有属性

class Secretive:
    def __accessible(self):
        print("you can't see me,unless you're calling internally")
    def accessible(self):
        print("The secret message is:")
        self.__accessible()
s = Secretive()
s.accessible()

# 运行结果：
# The secret message is:
# you can't see me,unless you're calling internally

class Foo:
 
    def __init__(self, name, age ,gender):
        self.name = name
        self.age = age
        self.gender = gender
 
    def eat(self):
        print "%s,%s岁,%s,吃奶" %(self.name, self.age, self.gender)
 
    def he(self):
        print "%s,%s岁,%s,喝水" %(self.name, self.age, self.gender)
 
    def shui(self):
        print "%s,%s岁,%s,睡觉" %(self.name, self.age, self.gender)
 
a = Foo('jack', 10, '男')
a.eat()
a.he()
a.shui()
 
b = Foo('rose', 11, '女')
b.eat()
b.he()
b.shui()

class Animal:
 
    def eat(self):
        print "%s 吃 " %self.name
 
    def drink(self):
        print "%s 喝 " %self.name
 
    def shit(self):
        print "%s 拉 " %self.name
 
    def pee(self):
        print "%s 撒 " %self.name
 
class Cat(Animal):
 
    def __init__(self, name):
        self.name = name
        self.breed ＝ '猫'
 
    def cry(self):
        print '喵喵叫'
 
class Dog(Animal):
 
    def __init__(self, name):
        self.name = name
        self.breed ＝ '狗'
 
    def cry(self):
        print '汪汪叫'
 
# ######### 执行 #########
 
c1 = Cat('猫one')
c1.eat()
 
c2 = Cat('猫two')
c2.drink()
 
d1 = Dog('狗one')
d1.eat()

class Person(object):
    def __init__(self,name,age):  #执行Person.__init__(self,name,age)时就会将传入的参数执行一遍
        self.name = name          #所以在BlackPerson中不仅有name,age而且还有sex
        self.age = age
        self.sex = "normal"
    def talk(self):
        print("person is talking....")

class WhitePerson(Person):
    pass

class BlackPerson(Person):
    def __init__(self,name,age,strength):     #先覆盖，再继承，再重构
        #先覆盖父类的__init__方法，再继承父类__init__，再加自己的参数
        Person.__init__(self,name,age)        #先继承父类Person，这里self就是BlackPerson本身
        #先将name,age传给子类BlackPerson,然后调用Person.__init__构造方法将参数出入父类（）
        self.strength = strength              #然后再重构自己的方法,即写自己的参数
        print(self.name,self.age,self.sex)
        print(self.strength)
    def talk(self):
        print("black balabla")
    def walk(self):
        print("is walking....")

b = BlackPerson("wei er smith",22,"Strong")
b.talk()
b.walk()


# 运行结果：
# wei er smith 22 normal
# Strong
# black balabla
# is walking....
# person is talking....

class Animal:
    def __init__(self, name):    # Constructor of the class
        self.name = name
    def talk(self):              # Abstract method, defined by convention only
        raise NotImplementedError("Subclass must implement abstract method")

class Cat(Animal):
    def talk(self):
        return 'Meow!'

class Dog(Animal):
    def talk(self):
        return 'Woof! Woof!'

animals = [Cat('Missy'),
           Dog('Lassie')]

for animal in animals:
    print(animal.name + ': ' + animal.talk())

# 运行结果：
# Missy: Meow!
# Lassie: Woof! Woof!

错误示例：
 
class Person(object):
    def __init__(self, name):
        self.name = name
 
    @staticmethod  # 把eat方法变为静态方法
    def eat(self):
        print("%s is eating" % self.name)
 
 
d = Person("xiaoming")
d.eat()  
 
############## 
 
结果：
TypeError: eat() missing 1 required positional argument: 'self'

正确示例： 
 
 
class Person(object):
    def __init__(self, name):
        self.name = name
 
    @staticmethod  # 把eat方法变为静态方法
    def eat(x):
        print("%s is eating" % x)
 
 
d = Person("xiaoming")
d.eat("jack")   
 
#就把eat方法当作一个独立的函数给他传参就行了

错误示例： 
 
class Person(object):
    def __init__(self, name):
        self.name = name
 
    @classmethod  # 把eat方法变为类方法
    def eat(self):
        print("%s is eating" % self.name)
 
 
d = Person("xiaoming")
d.eat()  
 
###########   
 
结果： 
AttributeError: type object 'Person' has no attribute 'name'

class Person(object):
    name="杰克"
    def __init__(self, name):
        self.name = name
 
    @classmethod  # 把eat方法变为类方法
    def eat(self):
        print("%s is eating" % self.name)
 
 
d = Person("xiaoming")
d.eat()

错误示例： 
 
class Person(object):
 
    def __init__(self, name):
        self.name = name
 
    @property  # 把eat方法变为属性方法
    def eat(self):
        print("%s is eating" % self.name)
 
 
d = Person("xiaoming")
d.eat()  
 
 
########## 
结果： 
TypeError: 'NoneType' object is not callable

class Person(object):
 
    def __init__(self, name):
        self.name = name
 
    @property  # 把eat方法变为属性方法
    def eat(self):
        print("%s is eating" % self.name)
 
 
d = Person("xiaoming")
d.eat

class Flight(object):
    def __init__(self,name):
        self.flight_name = name

    def checking_status(self):
        print("checking flight %s status " % self.flight_name)
        return  1

    @property
    def flight_status(self):
        status = self.checking_status()
        if status == 0 :
            print("flight got canceled...")
        elif status == 1 :
            print("flight is arrived...")
        elif status == 2:
            print("flight has departured already...")
        else:
            print("cannot confirm the flight status...,please check later")

f = Flight("CA980")
f.flight_status

class Dog(object):
    def __init__(self,name):
        self.name = '实例变量'
        self.name = name
    def __call__(self, *args, **kwargs):
        print("running call")
        print(args,kwargs)
d = Dog("ChenRonghua")
d(name='tom')               # 如果只实例化，而不d()调用，__call__函数不会执行

# 运行结果：
# running call
# () {'name': 'tom'}

class Foo:
    def __str__(self):
        return 'alex li'
obj = Foo()
print(obj)     # 输出：alex li

class abc:
    def __init__(self,age):
        self.age=age
    def __add__(self,obj):
        return self.age+obj.age
a1=abc(18)
a2=abc(20)
print(a1+a2)
#执行结果：38

class Province:
    country = 'China'
    def __init__(self, name, count):
        self.name = name
        self.count = count
    def func(self, *args, **kwargs):
        print('func')
# 获取类的成员，即：静态字段、方法、
print(Province.__dict__)
# 输出：{'country': 'China', '__module__': '__main__', 'func': <function func at 0x10be30f50>, '__init__': <function __init__ at 0x10be30ed8>, '__doc__': None}

obj1 = Province('HeBei',10000)
print(obj1.__dict__)
# 获取 对象obj1 的成员
# 输出：{'count': 10000, 'name': 'HeBei'}

obj2 = Province('HeNan', 3888)
print(obj2.__dict__)
# 获取 对象obj1 的成员
# 输出：{'count': 3888, 'name': 'HeNan'}

class Foo:
    """ 输出类的描述类信息 """
    def func(self):
        pass
print(Foo.__doc__) #运行结果：描输出类的描述类信息

class Foo(object):
    def __getitem__(self, key):
        print('__getitem__', key)

    def __setitem__(self, key, value):
        print('__setitem__', key, value)

    def __delitem__(self, key):
        print('__delitem__', key)

obj = Foo()
result = obj['k1']           # __getitem__ k1
obj['k2'] = 'wupeiqi'        # __setitem__ k2 wupeiqi
del obj['k1']                # __delitem__ k1

class Foo:
    def __init__(self,name,age):
        self.name=name
        self.age=age
        self.li=[1,2,3,4,5,6,7]
    def __getitem__(self, item):  # 匹配:对象[item]这种形式
        if isinstance(item,slice):  # 如果是slice对象，返回切片后的结果
            return self.li[item]  # 返回切片结果
        elif isinstance(item,int):  # 如果是整形，说明是索引
            return item+10
    def __setitem__(self, key, value):  # 匹配:对象[key]=value这种形式
        print(key,value)
    def __delitem__(self, key):  # 匹配:del 对象[key]这种形式
        print(key)
    def __getslice__(self,index1,index2):
        print(index1,index2)
 
li=Foo("alex",18)
print(li[3:5])
#执行结果：
[4, 5]

class Foo:
    def __init__(self,name,age):
        self.name=name
        self.age=age
    def __iter__(self):
        return iter([1,2,3,4,5])  # 返回的是一个迭代器
li=Foo("alex",18)
 
# 1.如果类中有__iter__方法，他的对象就是可迭代对象
# 2.对象.__iter()的返回值是一个迭代器
# 3.for循环的如果是迭代器，直接执行.next方法
# 4.for循环的如果是可迭代对象，先执行对象.__iter()，获取迭代器再执行next
 
for i in li:
    print(i)
#执行结果：
1
2
3
4
5

class User(object):
    def __init__(self,name,age):
        print('__init__')

    def __new__(cls, *args, **kwargs):
        print("__new__",args,kwargs)
        return object.__new__(cls)         # 调用一下object的__new__方法否则不往下走
d = User('tom',100)

# 运行结果：
# __new__ ('tom', 100) {}
# __init__