[flask] update and delete crud of data

Premise ： Need to generate data table

The following steps 1 to 6 are the operation steps for generating data tables

First step ： Database configuration

#  Configuration variables of the database 
HOSTNAME = '127.0.0.1'
PORT = '3306'
DATABASE = 'test'
USERNAME = 'root'
PASSWORD = 'root'
DB_URI = 'mysql+pymysql://{}:{}@{}:{}/{}?charset=utf8mb4'.format(USERNAME,PASSWORD,HOSTNAME,PORT,DATABASE)

The second step ： Create database engine

engine=create_engine(DB_URI)

The third step ： Test whether the data connection is successful

with engine.connect() as conn:
    res=conn.execute('select 1')
    print(res.fetchone())

Step four ： Create base class

Base=declarative_base(engine)

Step five ： Create model classes

class Person(Base):
    __tablename__='t_person'  # Create table name , It is best to t_ start 
    id=Column(name='id',type_=Integer,primary_key=True,autoincrement=True)
    name=Column(name='name',type_=String(255))
    age=Column(name='age',type_=Integer)
    address=Column(name='address',type_=String(255))
    country=Column(name='country',type_=String(50))  # New fields added after the table is created 
    city=Column(name='city',type_=String(50))        # New fields added after the table is created 

    def __str__(self):
        return ' full name :{}- Annual collar :{}- Address :{}- Country :{}- City :{}'.format(self.name,self.age,self.address,self.country,self.city)

Step six ： Create a data table based on the model class

#Base.metadata.drop_all()
Base.metadata.create_all()

Step seven ： establish session object

session=sessionmaker(engine)()    # Be careful sessionmaker Returns a function 

One 、 Modify the data

First, find the object from the database , Then modify the data to the data you want , Do it last commit The data can be modified by operation .

give an example 1：
Name it zz The characters , Change the name to jmeter

p1=session.query(Person).filter(Person.name=='zz').first()
p1.name='jmeter'
session.commit()

give an example 2：
Name all names as zz The characters , Change the name to jmeter

res=session.query(Person).filter(Person.name=='zz').all()
print(res)
for i in res:
    i.name='flask'
session.commit()

Two 、 Delete data

First, find the object from the database , Then delete this data , Do it last commit Then you can delete the data .

p1=session.query(Person).filter(Person.name=='kb').first()
session.delete(p1)
session.commit()

Particular attention ：
p1=session.query(Person).filter(Person.name=='kb').first()p1 It's the object , You can delete ;
p2=session.query(Person).filter(Person.name=='kb').all()p2 It's a list object , You cannot delete a list object , If you want to delete a list object , adopt for Cyclic operation
The code is as follows

def delete():
    res1 = session.query(Person).filter(Person.sal <= 3000).all()
    print(res1)
    for i in res1:
        session.delete(i)
    session.commit()