Python learning Day13 Python object-oriented learning

Object Oriented Programming in Python

Object Oriented Programming - Object Oriented Programming, OOP for short, is a kind of programming idea. OOP regards the object as the basic unit of the program, an object contains data and functions to manipulate the data.

Process-oriented programming treats a computer program as a series of commands, that is, the sequential execution of a set of functions. In order to simplify the program design, the process-oriented function is further divided into sub-functions, that is, the large function is divided into small functions to reduce the complexity of the system.

In object-oriented programming, a computer program is regarded as a collection of objects, and each object can receive messages from other objects and process these messages. The execution of a computer program is a series of messages passed between objects. .

In Python, all data types can be treated as objects, and of course custom objects are also possible. The custom object data type is the concept of class in object-oriented.

We use an example to illustrate the difference between procedure-oriented and object-oriented program flow.

Suppose we want to deal with student grade sheets. To represent a student's grades, a procedure-oriented program can be represented by a dict:

std1 = { 'name': 'Michael', 'score': 98 }
std2 = { 'name': 'Bob', 'score': 81 }

And processing student grades can be implemented through functions, such as printing student grades:

def print_score(std):
    print('%s: %s' % (std['name'], std['score']))

If we adopt the idea of ​​object-oriented programming, we prefer not to think about the execution flow of the program, but Studentthis data type should be regarded as an object , which has nameand scorethese two properties (Property) . If you want to print a student's grades, you must first create an object corresponding to the student, and then send a print_scoremessage to the object to let the object print out its own data.

class Student(object):

    def __init__(self, name, score):
        self.name = name
        self.score = score

    def print_score(self):
        print('%s: %s' % (self.name, self.score))

Sending a message to an object is actually calling the associated function corresponding to the object, which we call the method of the object . Object-oriented programs are written like this:

bart = Student('Bart Simpson', 59)
lisa = Student('Lisa Simpson', 87)
bart.print_score()
lisa.print_score()

Object-oriented design ideas come from nature, because in nature, the concepts of classes and instances are natural. Class is an abstract concept. For example, we define Class—Student, which refers to the concept of students, while Instances are specific Students. For example, Bart Simpson and Lisa Simpson are two specific Students.

Therefore, the object-oriented design idea is to abstract the Class and create the Instance according to the Class.

Object-oriented abstraction is higher than functions, because a Class contains both data and methods for manipulating data.

summary

Data encapsulation, inheritance and polymorphism are the three major characteristics of object-oriented.