Process oriented programming

The core of process oriented is process, which refers to the process of solving problems, that is, what to do first, what to do again, and what to do finally.

For example, the elephant is divided into several parts in the refrigerator:

1. Open the refrigerator door

2. Put the elephant in

3. Close the refrigerator door

Advantages: process complex problems and simplify them.

Disadvantages: one hair affects the whole body, poor expansibility and poor maintainability.

Application scenario: places that do not require high scalability.

 

 

 

Object oriented concept

Concept of object

1. In the procedure:

Functions are containers for data.

Objects are containers for data and functions.

2. In real life:

Everything is an object.

Object is the combination of characteristics and skills.

Comparison with process oriented

Advantages: strong expansibility and maintainability.

Disadvantages: high programming complexity.

Application scenario: places with high scalability requirements.

Example: course selection system

def choose_course(stu_dict, course):
    stu_dict['course'].append(course)
    print('%s Successful course selection %s' % (stu_dict['name'], stu_dict['course']))


# Students as objects
stu1 = {
    # Use names, etc. as features
    'name': 'tom',
    'age': 18,
    'gender': 'male',
    'course': [],
    # Take the function of course selection as a skill
    'choose_course': choose_course
}
# Students as objects
stu2 = {
    # Use names, etc. as features
    'name': 'jerry',
    'age': 18,
    'gender': 'male',
    'course': [],
    # Take the function of course selection as a skill
    'choose_course': choose_course
}
# The calling function passes itself as an argument
stu1['choose_course'](stu1, 'python')
stu2['choose_course'](stu2, 'python')

 

Results:

 

 

 

 

 

  Class definition and object generation

Concept of class

Object is a combination of characteristics and skills.

Class is the combination of a series of similar characteristics and skills of objects.

For different classification standards, the classification classes are not necessarily the same.

In real life:

There are objects before classes.

In the program:

First define the class and then call the class to generate the object.

Class definition

Define the syntax of the class:

class name ():

Class body code

It should be noted that the naming method of class names is generally hump body.

When executing code for a class:

1. Execute the class body code immediately.

2. Generate a class namespace, and put the names generated by the execution of class body code into the class namespace.

3. Bind the class namespace to__ dict__， Use class name__ dict__ To view the namespace of a class.

Still take the student course selection system as an example:

class Student():
    # Define a common attribute
    school = 'university'

    # Define a skill(function)
    def choose_course(stu_dict, course):
        stu_dict['course'].append(course)
        print('%s Successful course selection %s' % (stu_dict['name'], stu_dict['course']))


# View the namespace of the class
print(Student.__dict__)
# Generate object
# Call the class to generate an object. By default, an empty object is generated{}
stu1 = Student()
print(stu1.__dict__)

 

Results:

 

 

 

Custom object unique properties

　　

class Student():
    # Define an attribute
    school = 'SH'

    # Initialization method
    # Call the function automatically triggered by the class
    def __init__(self, name, age, gender, course=None):
        if course is None:
            course = []
        self.name = name
        self.age = age
        self.gender = gender
        self.course = course
        # return None # You cannot have a return value in this method

    # Define a skill(function)
    def choose_course(self, course):
        self.course.append(course)
        print('%s Successful course selection %s' % (self.name, self.course))


stu1 = Student('tom', 18, 'male')
print(stu1.__dict__)

 

When the function is called:

1. Get an empty object

2. Called student__ dict__

3. Get an initialization result

Results:

 

 

Find order of attributes

Class attribute: the attribute written in the class is the class attribute

Object attributes: attributes in the object's own namespace are object attributes

Class properties look up the name in the namespace of the class.

The object attribute cannot be found in the namespace of the object. If it cannot be found, go to the namespace of the class.

Call method

Class, the class can call, and the object can also call.

However, it is recommended to call the object, because the object will pass itself to the function as the first parameter.

Therefore, when defining an object, it is recommended to write the first parameter as self (representing yourself).