使用 flask 创建数据库，既未设置 SQLALCHEMY_DATABASE_URI 也未设置 SQLALCHEMY_BINDS

Question

I have a problem creating a database using flask, Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set; I always get this error

Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:".

from flask import Flask, render_template, request
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///friends.db'

class Friends(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    name = db.Column(db.String(200), nullable=False)
    date_created = db.Column(db.DateTime, default = datetime.utcnow)

    def __repr__(self):
            return '<Name %r>' % self.id

Answer 1

You need to move the db URI config to the line before instantiating a sqlalchemy object. Otherwise SQLAlchemy won't receive that data during instantiation.

Solution

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///friends.db' # Don't have this line below the next
db = SQLAlchemy(app)