Object-oriented members of the class of 1--

Object-oriented members of the class of 1--

Object-oriented three characteristics: 1. Package 2. 3. polymorphism inheritance

opp can do is break down the code, the code redundancy and minimize the existing code and then write a custom program, rather than modifying the code field, or start from scratch

First, the members of the class:

1. Field: ordinary fields, static fields

2. Methods: General methods, class methods, static methods

3. Properties

class Person:
    country = 'CN'     #静态字段
    __money = 99999                    #私有静态字段
    def __init__(self,name):
        self.name = name     #普通字段
        self.__age = 30                #私有普通字段
    def show(self):        #普通方法
        self.__think()
        return self.__age
    @classmethod           #类方法
    def cls_func(cls):
        return cls.__money
    @staticmethod
    def static_func():
        return  123
    @property
    def nature(self):    #属性
        return '鸽子' 
    def __think(self):       #私有方法
        return '画个圈圈'
           

Static fields belong to the class, leaving only one in memory

Common fields belong to the object, each object stored in each

Common methods belong to the object, comprising at least one parameter of self, invoked by the object

Class by the class method calls, comprising at least one parameter CLS,

Static class methods are called, no parameters self

Properties There are two forms defined above using a decorator, the following embodiment is a static field

def nature(self):
    return '鸽子'
na = property(nature)

Public and private

Private static field, __money = 99999, 错误：Person.__moneycan be accessed by indirect methods,

Private field,self.__age = 30，错误：obj.__age

Private method, error: obj .__ think ()

* Ps: have to access private property, you can through the object ._ class __ attribute name * obj._Person__money

self

self usually the name of the first parameter to the method of the class, Python will automatically fill in the instance of an object (that is, implicitly main method call), does not have to be called self, location is the key.

Second, special member (part)

__init__    __str__     __call__   __add__   __dict__   __doc__    __name__
__getitem__    __setitem__   __delitem__
__getattr__    __setattr__

---

class A:
    '''nothing....'''
    def __init__(self,data):    
       self.data = data
    def __str__(self,data):
        return self.data
    def __call__(self):
        print('Hellow')
    def __add__(self,other):
        return self.data + other       

__init__ When # constructor, each instance is created, Python will automatically call it, in addition to any parameters passed explicitly name the class, but also invisible incoming new instance.

__str__ When you want to print an object, running__str__

__add__ Objects appear in the "+" expression, will run__add__

__call__ When objects are called, will run__call__

__dict__All members return a dictionary of all the classes or objects

__doc__ Returning to the description information of the class

__name__ Returns the name of the class

a = A(1)
print(a)        # A
a()             # Hellow
print(a + 2)    #  3
print(a.__dict__)    # {'data': 1}    
print(a.__doc__) #nothing...
print(a.__class__.__name__)   # A

Not defined __dict__and __doc__, why not being given? , But also because all the classes inherit the default object;: class A (object) ; redefining overwrites the original function, does not make sense.

class B:
    def __init__(self,number):
        self.number = number
        self.dic = {'k1':1,'k2':2,'k3':3,}   
    def __getitem__(self, key):
        return self.dic[key]
    def __setitem__(self, key, value):
        self.dic[key] = value
    def __delitem__(self, key):
        del self.dic[key]
b =B(88)
n = b['k1']   #触发 __getitem__
print(n)   # 1
b['k4'] = 4  #触发 __setitem__
print(b.dic)  #{'k1': 1, 'k2': 2, 'k3': 3, 'k4': 4}
del b['k2'] #触发__delitem__
print(b.dic)  #{'k1': 1, 'k3': 3, 'k4': 4}       

---

class C:
    pass        
c = C()
c.name = 'Sroxi'
print(c.name)  # Sroxi

Class C, without any defined, c.name = 'Sroxi' is how to achieve?

- triggered the object's __setattr__methods, subclass does not make sense to rewrite the same

class Foo:
    def __init__(self):
        object.__setattr__(self, 'info', {})  #在对象中设置值的本质,注意：这里info带引号
    def __setattr__(self, key, value): 
        #c.name = 'Sroxi'，触发该方法，在object中有字典这样的容器进行接收
        self.info[key]=value
    def __getattr__(self, item): 
        #c.name触发该方法，将字典中的对应的value进行返回
        return self.info[item]