使用postgresql部署Flask应用程序并获取AttributeError：'drivername‘对象没有’drivername‘属性

Question

当我尝试将我的应用程序部署到Heroku上时，我得到了这个错误日志。

2020-07-12T03:19:13.340263+00:00 app[web.1]:   File "/app/app/__init__.py", line 35, in <module>
2020-07-12T03:19:13.340263+00:00 app[web.1]:     db.Model.metadata.reflect(db.engine)
2020-07-12T03:19:13.340263+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 943, in engine
2020-07-12T03:19:13.340264+00:00 app[web.1]:     return self.get_engine()
2020-07-12T03:19:13.340264+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 962, in get_engine
2020-07-12T03:19:13.340264+00:00 app[web.1]:     return connector.get_engine()
2020-07-12T03:19:13.340265+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 555, in get_engine
2020-07-12T03:19:13.340265+00:00 app[web.1]:     options = self.get_options(sa_url, echo)
2020-07-12T03:19:13.340265+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 570, in get_options
2020-07-12T03:19:13.340265+00:00 app[web.1]:     self._sa.apply_driver_hacks(self._app, sa_url, options)
2020-07-12T03:19:13.340268+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.8/site-packages/flask_sqlalchemy/__init__.py", line 883, in apply_driver_hacks
2020-07-12T03:19:13.340268+00:00 app[web.1]:     if sa_url.drivername.startswith('mysql'):
2020-07-12T03:19:13.340269+00:00 app[web.1]: AttributeError: 'NoneType' object has no attribute 'drivername'

这是我的init文件

app = Flask(__name__)

# Ensure responses aren't cached
@app.after_request
def after_request(response):
    response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
    response.headers["Expires"] = 0
    response.headers["Pragma"] = "no-cache"
    return response


##where to find the database and initialize SQLAlchemy
app.config['SQLALCHEMY_DATABASE_URI'] = os.environ.get('DATABASE_URL')
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app) 


##option to tell SQLALchemy that for every model it should just 
#look at the columns that already exist in the table. This is called reflecting
db.Model.metadata.reflect(db.engine)

class Congress(db.Model):
    __tablename__ = 'sen'
    __table_args__ = { 'extend_existing': True }
    id = db.Column(db.Text, primary_key=True) 

过程文件

web: flask db upgrade; gunicorn app:app

我不确定如何补救这种情况，任何帮助都将不胜感激。

Answer 1

当你在本地运行它的时候，它能工作吗？

问题看起来像是在环境变量DATABASE_URL中，当你部署到heroku时，你是如何声明这个问题的？