After learning database, we can use database to make a user management system. Realize the functions of registration, login, view, delete users, etc.
Step 1: specifically divided into two parts, the first part is to connect the database, and create a table to encapsulate the table into a class.
The specific implementation is as follows:

from sqlalchemy import create_engine,Column,Integer,SmallInteger,String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

engine=create_engine("mysql+pymysql://root:westos@192.168.122.191/pymysql",
                     encoding='utf8',
                     # echo=True
                     )

Session =sessionmaker(bind=engine)

session=Session()

Base=declarative_base()

class Users(Base):
    __tablename__='Users'
    id =Column(Integer,primary_key=True,autoincrement=True)
    name=Column(String(20),nullable=False)
    password=Column(String(20),nullable=False)
    email=Column(String(30),unique=True)

    def __repr__(self):
        return self.name
if __name__ == '__main__':
    Base.metadata.create_all(engine)

After encapsulation, the management system can be written.
The specific implementation is as follows:

import db

cookie={}

class UserManage(object):

    def login(self,name,password):
        #Get the user name and password from the database. Verify whether it is correct. If it is correct, the login succeeds. Otherwise, it fails.
        obj=db.session.query(db.Users).filter_by(name=name).filter_by(password=password).first()
        if obj:
            print("%s Login successfully"%name)
            cookie['name']=name
        else:
            print("Incorrect user name or password.")
    def logout(self):
        cookie.pop('name')
        print("Logout succeeded.")
    def register(self,user,password):
        #Get information from the database. If the user already exists, the user will be prompted to exist. Otherwise, the registration is successful.
        username = db.session.query(db.Users).filter_by(name=user).first()
        if username:
            print("The user already exists.")
        else:
            obj=db.Users(name=user,password=password)
            db.session.add(obj)
            db.session.commit()
            print("%s User registration succeeded."%user)
    def deltel(self,user):
        #Get object information from the database. If so, delete.
        obj=db.session.query(db.Users).filter_by(name=user).first()
        if obj:
            print(obj)
            db.session.delete(obj)
            db.session.commit()
            print("%s User deleted successfully."%user)
        else:
            print("The user does not exist.")
    def is_exists(self):
        obj=db.session.query(db.Users).all()
        print(obj)

if __name__ == '__main__':
    db.Base.metadata.create_all(db.engine)
    user1=UserManage()
    # Register with westos,
    user1.register('westos','westos')
    #Register with westos1
    user1.register('westos1','westos')
    #Verifying landing
    user1.login('westos','westos')
    # user1.deltel('westos')
    #Query all users.
    user1.is_exists()

Below is the result of our program running.

We can see that the content of the database is consistent, which shows that our system is ready.