And a method of binding non-binding

Binding method:

Method Object Binding Binding Method / Class

Binding method: special, who is who is going to bind to the tune, and will pass over itself

Binding methods of the class: binding to class, call the class, the class itself will pass over

Binding class methods used in any place?

- without going through the object, only need to be able to get something through the class when the class of binding method

- binding method class may be adjusted by the object

'''
类中使用@classmethod修饰的方法就是绑定到类的方法，这类方法专门为类定制，通过类名调用绑定到类的方法时，会将类本身当做参数传给类方法的第一个参数
'''
class Operate_database():
    host='192.168.0.5'
    port='3306'
    user='lzs'
    password='1234'
    
    @classmethod
    def connect(cls):##约定俗成第一个参数名为cls，也可以定义为其他参数名
        print(cls)
        print(cls.host+":"+cls.port+' '+cls.user+'/'+cls.password)
Operate_database.connect()

##<class '__main__.Operate_database'>
##192.168.0.5:3306 abc/123456

Unbound methods:

@Staticmethod modified using internal methods in the class is the non-binding method, and ordinary methods such defined functions without distinction, not tied to an object or class, anyone can call, automatically and without the effect of traditional values

import hashlib

class Operate_database():
    def __init__(self,host,port,user,password):
        self.host=host
        self.port=port
        self.user=user
        self.password=password
        
        @staticmethod
        def get_password(salt,password):
            m=hashlib.md5(salt.encode('utf=8')) ##加盐处理
            m.update(password.encode('utf-8'))
            return m.hexdigest()
hash_password=Operate_database.get_password('lala','123456') ##通过类来调用
print(hash_password)
####f7a1cc409ed6f51058c2b4a94a7e1956


p=Operate_database('192.168.0.5','3306','abc','123456')
hash_password=p.get_password(p.user,p.password)  ##也可以通过对象调用
print(hash_password)

Derived class:

Inherited his father's class at the same time they have init, then the parent class init also need

Class combinations:

You can refer to the class object / passing as a parameter / value as return / as a container element, similar to the function object

Diamond inheritance problem:

The new class: inherited object classes, python3 in all new class

Classic: not inherit object's class, there are only python2

In the diamond inheritance when the breadth of the new class of priority (the apex of the tree finally found); Classic depth-first (in the end find a way, find in the end, find next)

Polymorphism and polymorphism:

A thing in a variety of forms, animal --- "human / pig / dog

##多态
import abc

class Animal(metaclass=abc.ABCmeta):
    @abc.abstractmethod
    def eat():
        print('eat')
class People(Animal):
    def eat():
        pass
class Pig(Animal):
    def eat():
        pass
    def run():###报错,因为规定了要有eat()属性
        def run():
            pass
        
###多态性
peo=People()
peo.eat()
peo1=People()
peo1.eat()
pig=Pig()
pig.eat()

def func(obj):
    obj.eat()
class Cat(Animal):
    def eat()
    pass
cat=Cat()
func(cat)

Ducks type:

Just looks like a duck, called like a duck, swim like a duck, is a duck

Class Package:

Hidden property, only inside the class can be accessed outside the class can not access

class Foo():
    __count=0
    def get_count(self):
        return self._count
f=Foo()
f.__count   ##报错
f._Foo__count   ##不能这样做

property attribute class

The method becomes property reference

class People():
    def __init__(self,height,weight):
        self.height=height
        self.weight=weight
        
    @property
    def bmi(self):
        return weight/(height**2)
    @bmi.setter
    def bmi(self,value)
        print('setter')
    @bmi.deleter
    def bmi(self):
        print('delter')
peo=People
peo.bmi

Binding method classes and objects and non-binding method:

There is no way decorator decorative object is bound methods, classes can call, but must pass a reference to self

Garnished with @classmethod decorator class method is a method of binding parameters write cls, cls is the class itself, an object can be called, or parameters cls class itself

Garnished with @staticmethod decorator method is non-binding approaches, is an ordinary