Flask SQL model missing one positional argument

Question

from flask import (Flask, render_template)
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://user:password@localhost/database'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    nickname = db.Column(db.String(80), unique=True)

    def __init__(self, id, nickname):
        self.id = id
        self.nickname = nickname

admin = User('admin')

This code throws TypeError: __init__() missing 1 required positional argument: 'nickname', so it seems like it expects me to manually set the id, though i probably shouldn't do it? I also tried executing User(nickname='admin'), but it doesn't seem to work. Thanks for the help

Answer 1

I don't know why you use __init__ at all. It will work without it

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    nickname = db.Column(db.String(80), unique=True)

# --- create tables in database ---

with app.app_context():
    db.create_all()

# --- create User, save it in database, get ID ---

with app.app_context():
    admin = User(nickname='admin')

    print('before:', admin.nickname, admin.id)

    db.session.add(admin)
    db.session.commit()

    print(' after:', admin.nickname, admin.id)

---

Full working code for SQLite so everyone could run it:

from flask import (Flask, render_template)
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)

#app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://user:password@localhost/database'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///data.sqlite'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    nickname = db.Column(db.String(80), unique=True)

#    def __init__(self, id, nickname):
#        self.id = id
#        self.nickname = nickname

# --- create tables in database ---

with app.app_context():
    db.create_all()

# --- get unique name from command line ---

import sys
if len(sys.argv) > 1:
    name = sys.argv[1]
else:
    name = 'admin'

# --- create User, save it in database, get ID ---

with app.app_context():
    admin = User(nickname=name)

    print('before:', admin.nickname, admin.id)

    db.session.add(admin)
    db.session.commit()

    print(' after:', admin.nickname, admin.id)

# --- show list of Users ---

with app.app_context():
    for user in db.session.execute(db.select(User)).all():
        user = user[0]
        print(user.id, user.nickname)