烧瓶 sqlalchemy 更新错误 - update() 缺少 1 个必需的位置参数：'self'答案

【问题标题】：flask sqlalchemy update error - update() missing 1 required positional argument: 'self'烧瓶 sqlalchemy 更新错误 - update() 缺少 1 个必需的位置参数：'self'
【发布时间】：2015-07-11 22:57:53
【问题描述】：

我正在用 flask-restful 构建一个 restful-api。下面的代码是[PUT]users/ api，通过json接受名为email的变量，通过reqparse进行解析，reqparse是flask-restful给出的方法。

class UserAPI(Resource):
    def __init__(self):
        self.reqparse = reqparse.RequestParser()
        self.reqparse.add_argument('email', type=str,
            help='No Email Provided', location='json')
        super(UserAPI, self).__init__()
    def put(self,id):
        args = self.reqparse.parse_args()
        user = User.update(email=args.email) #this is the code causing error
        return {id:user.email}
api.add_resource(UserAPI, '/api/users/<int:id>', endpoint='user')

方法“update”是一个自定义函数，如下所示：

def update(self, commit=True, **kwargs):
        """Update specific fields of a record."""
        for attr, value in kwargs.iteritems():
            setattr(self, attr, value)
        return commit and self.save() or self

但是，当我将 {"email":"admin@amdin.com"} 的 [put] 命令发送到 localhost/api/users/ 时，它给了我以下错误：

Traceback (most recent call last):
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask_restful\__init__.py", line 265, in error_router
    return original_handler(e)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\_compat.py", line 32, in reraise
    raise value.with_traceback(tb)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask_restful\__init__.py", line 265, in error_router
    return original_handler(e)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\_compat.py", line 32, in reraise
    raise value.with_traceback(tb)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\app.py", line 1475, in full_dispatch_request
    rv = self.dispatch_request()
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask_debugtoolbar\__init__.py", line 124, in dispatch_request
    return view_func(**req.view_args)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask_restful\__init__.py", line 446, in wrapper
    resp = resource(*args, **kwargs)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask_httpauth.py", line 61, in decorated
    return f(*args, **kwargs)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask\views.py", line 84, in view
    return self.dispatch_request(*args, **kwargs)
  File "C:\Users\NI\Envs\nektime\lib\site-packages\flask_restful\__init__.py", line 550, in dispatch_request
    resp = meth(*args, **kwargs)
  File "C:\Users\NI\projects\nektime\nektime\public\views.py", line 76, in put
    user = User.update(email=args.email)
TypeError: update() missing 1 required positional argument: 'self'

【问题讨论】：

从上面的代码很难看出：更新是如何定义的？它是类的方法还是函数？如果它是一个可以解释错误的函数（不在类内部）。

标签： python flask flask-sqlalchemy flask-restful

【解决方案1】：

您正在对 User 类而不是 User 的实例调用更新。您可以在调用更新之前实例化用户：

user = User.query.get(id)
user.update(email=args.email)

或者你可以更新一个@classmethod，让它把cls作为第一个参数而不是self，它会实例化一个用户。

【讨论】：