烧瓶和 SQL Alchemy 的断言错误

Question

我有以下烧瓶结构：

使用以下代码：

init.py

from press_app.views import app
from press_app import models

# Connect sqlalchemy to app
models.db.init_app(app)

@app.cli.command()
def init_db():
    models.init_db()

models.py

from flask_sqlalchemy import SQLAlchemy
import logging as lg
from press_app.views import app

# Create database connection object
db = SQLAlchemy(app)

class Content(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    author = db.Column(db.String(100), nullable=True)
    content = db.Column(db.String(700), nullable=True)
    description = db.Column(db.String(700), nullable=True)
    publishedAt = db.Column(db.DateTime())
    source = db.Column(db.String(100), nullable=True)
    title = db.Column(db.String(200), nullable=True)
    url = db.Column(db.String(1000), nullable=True)
    urlToImage = db.Column(db.String(1000), nullable=True)

    def __init__(self, author, content, description, publishedAt, source, title, url, urlToImage):
        self.author = author
        self.content = content
        self.description = description
        self.publishedAt = publishedAt
        self.source = source
        self.title = title
        self.url = url
        self.urlToImage = urlToImage

db.create_all()

def init_db():
    db.drop_all()
    db.create_all()
    db.session.commit()
    lg.warning('Database initialized!')

views.py

from flask import Flask, render_template
from press_app.models import Content

app = Flask(__name__)

# Config options - Make sure you created a 'config.py' file.
app.config.from_object('config')
# To get one variable, tape app.config['MY_VARIABLE']

@app.route('/')
def index():
    last_article = Content.query.order_by(Content.id.desc()).first()
    last_id = last_article.id

    # Derniers titres
    title1 = Content.query.get(last_id).title
    title2 = Content.query.get(last_id - 1).title

    return render_template("index3.html", titre1 = title1)

if __name__ == "__main__":
    app.run()

config.py

import os

basedir = os.path.abspath(os.path.dirname(__file__))
SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(basedir, 'app.db')

和run.py

from press_app import app
if __name__ == "__main__":
    app.run()

由于以下错误消息：

ImportError: cannot import name 'app' from partially initialized module 'press_app.views' (most likely due to a circular import) 

我选择直接在我的函数中移动views.py文件中的一个导入，如下：

views.py，第二版

from flask import Flask, render_template

app = Flask(__name__)

# Config options - Make sure you created a 'config.py' file.
app.config.from_object('config')
# To get one variable, tape app.config['MY_VARIABLE']

@app.route('/')
def index():
    from press_app.models import Content

    last_article = Content.query.order_by(Content.id.desc()).first()
    last_id = last_article.id

    # Derniers titres
    title1 = Content.query.get(last_id).title
    title2 = Content.query.get(last_id - 1).title

    return render_template("index3.html", titre1 = title1)

if __name__ == "__main__":
    app.run()

但是，我遇到了一个新的错误消息（错误 500），我无法解决，尽管我阅读了许多有关它的文档和 stackoverflow 消息。

AssertionError: The sqlalchemy extension was not registered to the current application.  Please make sure to call init_app() first.

我该如何解决这种情况？

Answer 1

这个问题是因为你在另一个文件中初始化模型，在另一个文件中初始化flask app，你的app需要在sqlalchemy对象之前初始化，这样你才能使用它。

所以你的文件应该是这样的。

views.py

from flask import Flask, render_template
from models import db

app = Flask(__name__)

# Config options - Make sure you created a 'config.py' file.
app.config.from_object('config')
# To get one variable, tape app.config['MY_VARIABLE']
db.init_app(app)
with app.app_context():
    db.create_all()
    db.session.commit()


@app.route('/')
def index():
    from models import Content

    last_article = Content.query.order_by(Content.id.desc()).first()
    last_id = last_article.id

    # Derniers titres
    title1 = Content.query.get(last_id).title
    title2 = Content.query.get(last_id - 1).title

    return render_template("index3.html", titre1 = title1)


if __name__ == "__main__":
    app.run()

models.py

from flask_sqlalchemy import SQLAlchemy
import logging as lg

# Create database connection object
db = SQLAlchemy()

class Content(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    author = db.Column(db.String(100), nullable=True)
    content = db.Column(db.String(700), nullable=True)
    description = db.Column(db.String(700), nullable=True)
    publishedAt = db.Column(db.DateTime())
    source = db.Column(db.String(100), nullable=True)
    title = db.Column(db.String(200), nullable=True)
    url = db.Column(db.String(1000), nullable=True)
    urlToImage = db.Column(db.String(1000), nullable=True)

    def __init__(self, author, content, description, publishedAt, source, title, url, urlToImage):
        self.author = author
        self.content = content
        self.description = description
        self.publishedAt = publishedAt
        self.source = source
        self.title = title
        self.url = url
        self.urlToImage = urlToImage


def init_db():
    db.drop_all()
    db.create_all()
    db.session.commit()
    lg.warning('Database initialized!')