'引擎'对象没有属性'drivername'

Question

我在应用程序中集成了Flask和SQLAlchemy，但是可以理解，为什么在登录页面中获取大堆栈跟踪。现在我将在从Debian切换到Mac OS后执行这些错误。所有在virtuaelnv中使用过的库。

我现在所拥有的这些东西：
在flask_app.py 1）：

from flask import Flask, request, session 
from flask_sqlalchemy import SQLAlchemy 
from db import tables as dbTables 
from db.queries import engine as db_engine 

app = Flask(__name__, template_folder='./web/templates/', static_folder='./web/static/', static_url_path='') 
app.config['SECRET_KEY'] = 'some_secret_key' 
app.config['SQLALCHEMY_DATABASE_URI'] = db_engine 
db_connection = SQLAlchemy(app) 

import web.admin 
import web.views 

if __name__ == "__main__": 
    from web.admin import * 
    from web.views import * 
    app.run(port=8500, debug=True) 

2）它我queries.py，其中包含该字符串和代码采取和PostgreSQL数据库的一些数据：

import datetime 
from hashlib import sha256 
from time import gmtime, strftime 

import sqlalchemy 
import sqlalchemy.exc 
from sqlalchemy import and_, func, asc 
from sqlalchemy.orm import sessionmaker 

from tables import File as FileTable 
from tables import Users, FileServer, FileSpace, Catalog 

engine = sqlalchemy.create_engine("postgresql://dev:developer@localhost/csan", pool_size=20, max_overflow=0) 
Session = sessionmaker(bind=engine) 

# and some queries for DB 
# ... 

3）而这个堆栈跟踪，发送给http://localhost:8500/admin/login POST请求后：

AttributeError 
AttributeError: 'Engine' object has no attribute 'drivername' 

Traceback (most recent call last) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__ 
return self.wsgi_app(environ, start_response) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app 
response = self.make_response(self.handle_exception(e)) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception 
reraise(exc_type, exc_value, tb) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app 
response = self.full_dispatch_request() 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request 
rv = self.handle_user_exception(e) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception 
reraise(exc_type, exc_value, tb) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request 
rv = self.dispatch_request() 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request 
return self.view_functions[rule.endpoint](**req.view_args) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_admin/base.py", line 62, in inner 
return f(self, *args, **kwargs) 
File "/Users/savicvalera/code/Helenae/Helenae/helenae/web/admin.py", line 42, in login_view 
if helpers.validate_form_on_submit(form): 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_admin/helpers.py", line 47, in validate_form_on_submit 
return is_form_submitted() and form.validate() 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/form.py", line 310, in validate 
return super(Form, self).validate(extra) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/form.py", line 152, in validate 
if not field.validate(self, extra): 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/fields/core.py", line 200, in validate 
stop_validation = self._run_validation_chain(form, chain) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/wtforms/fields/core.py", line 220, in _run_validation_chain 
validator(form, self) 
File "/Users/savicvalera/code/Helenae/Helenae/helenae/web/forms.py", line 19, in validate_login 
user = get_user(self.login.data) 
File "/Users/savicvalera/code/Helenae/Helenae/helenae/web/forms.py", line 11, in get_user 
return db_connection.session.query(dbTables.Users).filter_by(name=user).first() 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 150, in do 
return getattr(self.registry(), name)(*args, **kwargs) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/sqlalchemy/util/_collections.py", line 910, in __call__ 
return self.registry.setdefault(key, self.createfunc()) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 139, in __init__ 
bind=db.engine, 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 780, in engine 
return self.get_engine(self.get_app()) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 797, in get_engine 
return connector.get_engine() 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 470, in get_engine 
self._sa.apply_driver_hacks(self._app, info, options) 
File "/Users/savicvalera/code/Helenae/lib/python2.7/site-packages/flask_sqlalchemy/__init__.py", line 739, in apply_driver_hacks 
if info.drivername.startswith('mysql'): 
AttributeError: 'Engine' object has no attribute 'drivername' 

Answer 1

除了一个Flask-SQLAlchemy已经为您生成了另一个会话之外，您正在创建第二个会话，并且您正在干涉Flask-SQLAlchemy。

导入db_connection并使用db_connection.session而不是创建新会话。