SQLAlchemy实例的更简洁的初始化

Question

It's my first attempt at sqlalchemy. I have a json file with my usr information and I would like to put them in a sqlite3 database file. It works but I find the instance initialization verbose since there are many columns in the table, as you can see below.

Is it possible to use a dictionary as input to initialize User() ? Something like a = User(usr) ?

import json                                                            
from sqlalchemy import *                                               
from sqlalchemy.ext.declarative import declarative_base                

engine = create_engine('sqlite:///tutorial.db', echo=True)             

Base = declarative_base()                                              

class User(Base):                                                      
    __tablename__ = 'users'                                            

    id = Column(Integer, primary_key=True)                             
    bbs_id = Column(String)                                            
    name = Column(String)                                              
    sex = Column(String, nullable=False)                               
    city = Column(String)                                              
    state = Column(String)                                             
    class_type = Column(String, nullable=False)                        
    class_id = Column(String, nullable=False)                          
    latitude = Column(Float)                                           
    longitude = Column(Float)                                          

    def __repr__(self):                                                
        return "<User(bbs_id='%s', name='%s'>" % (self.bbs_id, self.name)

Base.metadata.create_all(engine)                                       


with open('mydata.json') as fin:                                        
    usrs = json.load(fin)                                              

usr = usrs[0]                                                          

a = User(id=usr['id'], bbs_id=usr['bbs_id'], name=usr['name'])  

Answer 1

If you know the property names in the JSON object match the column names of the Python model, you can just change:

a = User(id=usr['id'], bbs_id=usr['bbs_id'], name=usr['name'])

to:

a = User(**usr)

Double-star/ dict unpacking passes each key/value pair of the dict as if it were an argument being passed by keyword. Since you didn't override __init__ for your model, it already allows and expects the arguments to be optional and passed by keyword, so this lines up perfectly.