使用Python/Flask/MySQL實現數據庫連接狀態時遇到困難

Question

我正在PythonAnywhere平臺上用Python/Flask/MySQL構建一個網站。我以前曾經和DB一起工作過（閱讀：db連接不是這裏的問題，它是設置/配置和調用），但是我想改變它以更符合Web開發（即應用程序/請求上下文）。

根據文檔和其他帖子（例如這個：Connect to a Database in Flask, Which Approach is better?），我已經嘗試過不同的配置。雖然信息量很大，但我仍然無法成功實施，希望有人能指出爲什麼它不起作用。

我試圖讓事情變得簡單，所以有一個MyApp.py文件，此刻的一切，它看起來像這樣：

from flask import Flask, render_template, session, request, redirect, url_for, g 
from flask.ext.mysql import MySQL 

app = Flask(__name__, static_url_path='') 
app.config["DEBUG"] = True 

def get_db(): 
    db = getattr(g, '_database', None) 
    if db is None: 
     db = g._database = connect_to_database() 
    return db 

@app.teardown_appcontext 
def teardown_db(exception): 
    db = getattr(g, '_database', None) 
    if db is not None: 
     db.close() 

def connect_to_database(): 
    mysql = MySQL() 
    app.config['MYSQL_DATABASE_USER'] = '{db_user}' 
    app.config['MYSQL_DATABASE_PASSWORD'] = '{db_password}' 
    app.config['MYSQL_DATABASE_DB'] = '{db}' 
    app.config['MYSQL_DATABASE_HOST'] = '{dbhost}' 
    dbcon = mysql.connect() 
    return dbcon 

@app.route('/', methods=["GET", "POST"]) 
def index(): 
    db_conn = get_db() 
    cursor = db_conn.cursor() 
    #... do my SQL stuff here ...# 
    return render_template("home_guest.html") 

它，當它到達mysql.connect（）函數和失敗我無法弄清楚爲什麼。以下是來自Python Anywhere服務器的錯誤日誌：

2017-06-20 02:03:23,228: Error running WSGI application 
2017-06-20 02:03:23,230: AttributeError: 'NoneType' object has no attribute 'config' 
2017-06-20 02:03:23,230: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 2000, in __call__ 
2017-06-20 02:03:23,230:  return self.wsgi_app(environ, start_response) 
2017-06-20 02:03:23,231: 
2017-06-20 02:03:23,231: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1991, in wsgi_app 
2017-06-20 02:03:23,231:  response = self.make_response(self.handle_exception(e)) 
2017-06-20 02:03:23,231: 
2017-06-20 02:03:23,231: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1567, in handle_exception 
2017-06-20 02:03:23,232:  reraise(exc_type, exc_value, tb) 
2017-06-20 02:03:23,232: 
2017-06-20 02:03:23,232: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1988, in wsgi_app 
2017-06-20 02:03:23,232:  response = self.full_dispatch_request() 
2017-06-20 02:03:23,232: 
2017-06-20 02:03:23,232: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1641, in full_dispatch_request 
2017-06-20 02:03:23,232:  rv = self.handle_user_exception(e) 
2017-06-20 02:03:23,232: 
2017-06-20 02:03:23,232: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1544, in handle_user_exception 
2017-06-20 02:03:23,233:  reraise(exc_type, exc_value, tb) 
2017-06-20 02:03:23,233: 
2017-06-20 02:03:23,233: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1639, in full_dispatch_request 
2017-06-20 02:03:23,233:  rv = self.dispatch_request() 
2017-06-20 02:03:23,233: 
2017-06-20 02:03:23,233: File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1625, in dispatch_request 
2017-06-20 02:03:23,233:  return self.view_functions[rule.endpoint](**req.view_args) 
2017-06-20 02:03:23,233: 
2017-06-20 02:03:23,233: File "/home/WazzalJohn/mysite/flask_app.py", line 83, in login 
2017-06-20 02:03:23,234:  conn = get_db() 
2017-06-20 02:03:23,234: 
2017-06-20 02:03:23,234: File "/home/WazzalJohn/mysite/flask_app.py", line 15, in get_db 
2017-06-20 02:03:23,234:  db = g._database = connect_to_database() 
2017-06-20 02:03:23,234: 
2017-06-20 02:03:23,234: File "/home/WazzalJohn/mysite/flask_app.py", line 40, in connect_to_database 
2017-06-20 02:03:23,234:  dbcon = mysql.connect() 
2017-06-20 02:03:23,234: 
2017-06-20 02:03:23,235: File "/home/WazzalJohn/.local/lib/python2.7/site-packages/flaskext/mysql.py", line 39, in connect 
2017-06-20 02:03:23,235:  if self.app.config['MYSQL_DATABASE_HOST']: 

任何建議或幫助，將不勝感激，謝謝。

Answer 1

您必須致電init_app才能初始化該應用以用於MySQL類。然後從擴展中訪問連接。這不會進入功能。

mysql = MySQL() 
app.config['MYSQL_DATABASE_USER'] = '{db_user}' 
app.config['MYSQL_DATABASE_PASSWORD'] = '{db_password}' 
app.config['MYSQL_DATABASE_DB'] = '{db}' 
app.config['MYSQL_DATABASE_HOST'] = '{dbhost}' 
mysql.init_app(app) 

@app.route('/') 
def index(): 
    c = mysql.connection.cursor() 
    ...