Python Learning Note 6: Object-oriented

I. Programming paradigm

Programming Paradigm

Programming is a programmer with a specific syntax + data structure + algorithm composed of code to tell the computer how to perform the task of the process, a program is a programmer in order to get a task result and a set of instructions, is so-called all roads to Rome, the way to achieve a task there are many different ways, The types of programming that are summed up by the characteristics of these different programming methods are the programming paradigm. Different programming paradigms essentially represent different solutions to various types of tasks, and most languages support only one programming paradigm, and of course some languages can support multiple programming paradigms at the same time. Two of the most important programming paradigms are process-oriented programming and object-oriented programming.

Process-oriented programming (procedural programming)
Procedural programming uses a list of instructions to tell the computer what to do step-by-step.
Process-oriented programming dependencies-you guessed-procedures, a procedure contains a set of steps to be computed, and the process is called Top-down languages, which is the procedure from the top to the next step, step by step from top to bottom, to solve the problem from beginning to end. The basic design idea is that the program starts with solving a big problem, and then breaks down a big problem into many small problems or sub-processes, and the process continues to decompose until the small problem is simple enough to be solved within a small step.

The problem is also obvious, that is, if you want to modify the program, you have to modify the part of the dependent parts you also have to modify, for example, if the program at the beginning you set a variable value of 1, but if other sub-procedures rely on the value of 1 of the variable to run correctly, If you change this variable, then you have to modify this process, if there is another subroutine dependent on the sub-process, it will have a series of effects, as the program becomes larger, the maintenance of this method will be more difficult.
So we generally think that if you just write some simple scripts to do some one-off tasks, it's great to use a process-oriented approach, but if the task you're dealing with is complex and needs to be iterative and maintainable, it's the most convenient way to use object-oriented.

Object-Oriented Programming

OOP programming is the use of "class" and "object" to create a variety of models to achieve a real-world description, the use of object-oriented programming because it can make the maintenance and extension of the program easier, and can greatly improve the efficiency of program development, in addition, An object-oriented program can make it easier for people to understand your code logic and make team development easier.

Several core features of object-oriented are as follows

Class
A class is an abstraction, a blueprint, a prototype for a class of objects that have the same properties. The properties of these objects are defined in the class (variables (data)), common methods

Object objects
An object is an instantiated instance of a class, a class must be instantiated before it can be called in the program, a class can instantiate multiple objects, each object can also have different properties, like human refers to everyone, each person refers to the specific object, people and people before there is a common, there are different

Encapsulation Package
The assignment of data in a class, internal invocation is transparent to external users, which makes the class A capsule or container in which the data and methods of the class are contained.

Inheritance inheritance
A class can derive subclasses, properties, methods defined in the parent class, automatic quilt class inheritance

Polymorphism Polymorphism
State is an important feature of object-oriented, simple point: "An interface, a variety of implementations," refers to a base class derived from a different subclass, and each subclass inherits the same method name, but also the method of the parent class to do a different implementation, this is the same thing shows a variety of forms.
Programming is actually a process of abstracting the concrete world, which is a manifestation of abstraction, abstracting the common denominator of a series of specific things, and then through this abstract thing, and dialogue with different concrete things.
Sending the same message to different classes of objects will have different behavior. For example, if your boss lets all employees start working at nine o'clock, he says "get started" at nine o'clock, instead of saying to the salesperson: "Start a sales job," say to the technician, "Start technical work", because "employee" is an abstract thing, so long as the employee can start to work, He knows that. As for each employee, of course, they do their job and do their jobs.
Polymorphism allows the object of a subclass to be used as an object of the parent class, a reference to a parent type to an object of its subtype, and the method called is the method of that subtype. The code that references and invokes the method is already determined before it is compiled, and the object pointed to by the reference can be dynamically bound during run time

Two. Object-oriented feature encapsulation

The package is best understood. Encapsulation is one of the object-oriented features and is the main feature of object and class concepts.

Encapsulation, which is the encapsulation of objective things into abstract classes, and classes can put their own data and methods only trusted class or object operation, to the untrusted information hiding.

Class Role (object):
n = 123 #类变量, common property for everyone, save overhead
N_list=[]
def __init__ (self,name,role,weapon,life_value=1000,money=500):
#构造函数
#在实例化时做一些类的初始化工作
self.name=name# instance variable (static property), scope is the instance itself
Self.role=role
Self.weapon=weapon
Self.__life_value=life_value
Self.money=money
def __del__ (self):
Print ("Brother Long is my idol!!!" ")
Def shot (self):
Print ("Name:%s Weapon:%s life_val:%s"% (Self.name,self.weapon,self.__life_value))

def __got_shot (self):
#print ("{name} got shot". Format (Name=self.name))
Self.__life_value-=10
def buy_gun (self,gun_name):
Print ("%s just bought%s"% (Self.name,self.weapon))
# __got_shot (self)

R1 = Role ("Tom", "police", "AK47")
#print (R1.liefe_value)
R1.buy_gun ("AK47")
r2 = Role ("Jack", "Teor", "B22")

# r1.n=100
# r1.n2=456
#del ROLE.N
# R1.n_list.append ("from R1")
# R2.n_list.append ("from R2")
# Print (R1.N,R1.N2)
# Print (R2.N)
# Print (ROLE.N)
# Print (r1.n_list)
# Print (role.n_list)

Inherited

One of the main functions of object-oriented programming (OOP) language is "inheritance". Inheritance refers to the ability to use all the functionality of an existing class and to extend these capabilities without rewriting the original class.

New classes created through inheritance are called "subclasses" or "derived classes."

The inherited class is called the base class, the parent class, or the superclass.

The process of inheritance is from the general to the special process.

To implement inheritance, it can be implemented through inheritance (inheritance) and combination (composition).

In some OOP languages, a subclass can inherit multiple base classes. However, in general, a subclass can have only one base class, and to implement multiple inheritance, it can be implemented by multilevel inheritance.

Inheritance concepts are implemented in three categories: implementation inheritance, interface inheritance, and visual inheritance.

Implementing inheritance is the ability to use the properties and methods of a base class without additional coding; O interface inheritance is the ability to use only the names of properties and methods, but the subclasses must provide the implementation; Visual inheritance is the ability of a subform (class) to use the appearance of a base form (class) and to implement code.

When considering using inheritance, it is important to note that the relationship between the two classes should be a "belongs" relationship. For example, the Employee is a person and the Manager is a person, so these two classes can inherit the People class. But the Leg class cannot inherit the person class, because the leg is not a human.

Abstract classes define only the generic properties and methods that will be created by the subclass.

OO development paradigm is roughly: dividing objects → abstract classes → organizing classes into hierarchical structures (inheritance and compositing) → Designing and implementing several stages with classes and instances.

class people:
    def __init__ (self,name):
        Self.name=name
    Def eat (self):
        Print ("{name} is eating!". Format (name=self.name))
    def sleep (self):
        Print ("{name} is sleeping". Format (Name=self.name))

Class Relation (object):
    def make_friends (self,obj):
        Print ("%s is making friends with%s"% (Self.name,obj.name))

Class Man (people,relation):
    Def eat (self):
        People.eat (self)
        Print ("Eating from class")

    def piao (self):
        Print ("%s is piaoing"% self.name)
Class women (people):

    def birth (self):
        Print ("%s is giving birth"% self.name)
M1=man ("Tom")
F1=women ("Jane")
M1.make_friends (F1)
# m1.eat ()
# F1.birth ()

Three. polymorphic

polymorphic  Polymorphism (POLYMORPHISN) is a technique that allows you to set a parent object to be equal to one or more of his child objects, after which the parent object can operate differently depending on the attributes of the child object currently assigned to it. To put it simply, it is a sentence: A pointer to the parent class type is allowed to be assigned a pointer to the child class type. So what is the role of polymorphism? We know that encapsulation can hide implementation details and make code modular; Inheritance can extend existing code modules (classes); they are all designed to-code reuse. And polymorphism is for another purpose--interface reuse! The role of polymorphism is to ensure that classes are called correctly when inheriting and deriving a property of an instance of any class in the family tree.  Pyhon does not directly support polymorphism, but can indirectly implement

Python Learning Note 6: Object-oriented