1. Three characteristics
Package
Many encapsulating the data object into ⼀ in. The function code is fixed to the package ⼀ code blocks, functions, objects, packaged into modules which belong thought encapsulated particular situation specific analysis such as you write ⼀ B is a very ⽜ function. this may also be referred to as that packaged in ⾯ to a subject thought. ⽆ is seemingly the more crucial ⼀ combination of content from the system to ⼀ ⼀ storing anything and Use. this is the package .
inherit
Submenu class can automatically have ⽗ like all other content in addition to private property. White said, and submenus can easily reach of children to Use East ⻄ father. But my friends, ⼀ given to a clear understanding of ⼀ a thing. You must have a father , after the reach of children submenus. order can not be chaotic, implementation inheritance in python is very simple. in a statement class, ⾯ add one hour for parentheses after the class name, you can complete inheritance. so what can be accessed using inherit it? when a simple two classes have the same function or feature from the point of view of code ⾯ layer may be recorded using the inherited form. ⽗ extraction ⼀ a class, the class ⽗ prepared by the same portions of the two classes. then two class inherit this class were taken on it. the benefits of this is written, we can avoid a lot of duplication of functions and write the code. If you go from a semantic analysis of the case. would be much simpler if the context is ⼀ species emerged x y. in this case, y is ⼀ kind of generalization of the concept. x than y more specific. it is then x y kind of submenus, such as cat is ⼀ animal cat inherited animal animals active. cats are also active. At this cat in the creation of the animals have a "dynamic" This property. As another example, the white fine bone ⼀ is a monster. Monsters day ⽣ there ⼀ relatively poor function called "Face to eat," White fine bone ⼀ out ⽣ know how to "eat the Face." At this point the white bone fine inheritance monster.
Polymorphism
With ⼀ objects, a variety of forms. In fact, this in python is not easy to explain white, because we ⼀ Use straight in. Just do not specifically. For example, we create ⼀ variables a = 10, we know this when a is an integer type, but we can make the program a = "alex", this time, a separate warranty into a string type. this is what we all know. but I'll tell you that. this is polymorphic resistance. ⼀ same variable may be a variety of forms
2. Type Ducks
python in a proverb that good, you look like a duck, then you are a duck.
class A:
def f1(self):
print('in A f1')
def f2(self):
print('in A f2')
class B:
def f1(self):
print('in A f1')
def f2(self):
print('in A f2')
obj = A()
obj.f1()
obj.f2()
obj2 = B()
obj2.f1()
obj2.f2()A and B two classes there is no coupling, but in a sense they are a unified standard.
The same function set with the same name, which facilitate the development of these two methods can become mutually duck typing.
Examples abound: str tuple list has index method, which is to unify the norm.
str bytes, etc. This is called cross-duck type.
3. Constraints class
There are two classes of constraints:
The first: an exception is thrown
Extraction ⽗ class and then defined the Remedies in ⽗ class. In this Remedies in nothing with a dry. ⼀ to throw exceptions on it. All submenus that such classes must override the Remedies otherwise. time of the visit will give an error.
class Payment:
def pay(self,money):
raise Exception("子类设置pay方法")
class QQpay(Payment):
def pay(self,money):
print(f"QQ支付{money}金额")
class Alipay(Payment):
def pay(self,money):
print(f"支付宝支付{money}金额")
class Wechatpay(Payment):
def zhifu(self,money):
print(f"微信支付{money}金额")
def pay(obj,money):
obj.pay(money)
obj1 = QQpay()
pay(obj1,100)
obj2 = Alipay()
pay(obj2,200)
obj3 = Wechatpay()
pay(obj3,300)
"""
QQ支付100金额
Traceback (most recent call last):
支付宝支付200金额
File "D:/pycharm demo/练习/代码练习.py", line 30, in <module>
pay(obj3,300)
File "D:/pycharm demo/练习/代码练习.py", line 20, in pay
obj.pay(money)
File "D:/pycharm demo/练习/代码练习.py", line 3, in pay
raise Exception("子类设置pay方法")
Exception: 子类设置pay方法
"""The second: metaclasses
Use metaclass described ⽗ class are given in ⼀ abstract Remedies metaclass. Such classes would have submenus give specific implementation of the abstract methods for the camera. Constraints may also play effect.
from abc import ABCMeta,abstractmethod
class Payment(metaclass=ABCMeta):
@abstractmethod
def pay(self,money):
pass
class QQpay(Payment):
def pay(self,money):
print(f"QQ支付{money}金额")
class Alipay(Payment):
def pay(self,money):
print(f"支付宝支付{money}金额")
class Wechatpay(Payment):
def zhifu(self,money):
print(f"微信支付{money}金额")
def pay(obj,money):
obj.pay(money)
obj1 = QQpay()
pay(obj1,100)
obj2 = Alipay()
pay(obj2,200)
obj3 = Wechatpay()
pay(obj3,300)
"""
QQ支付100金额
Traceback (most recent call last):
支付宝支付200金额
File "D:/pycharm demo/练习/代码练习.py", line 63, in <module>
obj3 = Wechatpay()
TypeError: Can't instantiate abstract class Wechatpay with abstract methods pay
"""4.super depth analysis
class A:
def f1(self):
print('in A f1')
def f2(self):
print('in A f2')
class Foo(A):
def f1(self):
super().f2()
print('in A Foo')
obj = Foo()
obj.f1()
"""
'in A f2'
'in A Foo'
"""
super可以下一个类的其他方法class A:
def f1(self):
print('in A')
class Foo(A):
def f1(self):
super().f1()
print('in Foo')
class Bar(A):
def f1(self):
print('in Bar')
class Info(Foo,Bar):
def f1(self):
super().f1()
print('in Info f1')
obj = Info()
obj.f1()
'''
in Bar
in Foo
in Info f1
'''
print(Info.mro()) # [<class '__main__.Info'>, <class '__main__.Foo'>, <class '__main__.Bar'>, <class '__main__.A'>, <class 'object'>]
super()严格按照类的mro顺序执行class A:
def f1(self):
print('in A')
class Foo(A):
def f1(self):
super().f1()
print('in Foo')
class Bar(A):
def f1(self):
print('in Bar')
class Info(Foo,Bar):
def f1(self):
super(Foo,self).f1()
print('in Info f1')
obj = Info()
obj.f1()
"""
in Bar
in Info f1
"""