Python 如何在SQLAlchemy中传递过滤条件中的模型参数

我正在使用SQLAlchemy来处理我目前正在开发的Flask webapp的数据库。作为网站的一项功能，我希望用户能够以指定位置的位置和半径作为参数搜索其他用户。所以很自然地，我对SQLAlchemy了解不多，我试着用这个表达：

profiles = User.query.filter(sqrt(abs(User.latitude - location.latitude)**2 + abs(User.longitude - location.longitude)**2) <= radius)

profiles = User.query.filter(User.is_nearby(latitude=location.latitude, longitude=location.longitude, radius=radius))

（我还删除了表达式中的

abs（）

函数，因为平方运算已经返回了唯一的正值..）

这是我的路线，而不是旧的表达：

profiles = User.query.filter(sqrt(abs(User.latitude - location.latitude)**2 + abs(User.longitude - location.longitude)**2) <= radius)

profiles = User.query.filter(User.is_nearby(latitude=location.latitude, longitude=location.longitude, radius=radius))

（仅供参考，然后我保存了代码，更新了数据库并重新启动了flask服务器）

我再次尝试了查询搜索，然后。。。 我得到了这个错误：

Traceback (most recent call last):
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2309, in __call__
   return self.wsgi_app(environ, start_response)
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2295, in wsgi_app
   response = self.handle_exception(e)
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1741, in handle_exception
   reraise(exc_type, exc_value, tb)
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
   raise value
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2292, in wsgi_app
   response = self.full_dispatch_request()
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1815, in full_dispatch_request
   rv = self.handle_user_exception(e)
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1718, in handle_user_exception
   reraise(exc_type, exc_value, tb)
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
   raise value
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1813, in full_dispatch_request
   rv = self.dispatch_request()
 File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1799, in dispatch_request
   return self.view_functions[rule.endpoint](**req.view_args)
 File "C:\Users\Frederik\Desktop\start\app\routes.py", line 136, in explore
   profiles = User.query.filter_by(sqrt(abs(User.latitude - location.latitude)**2 + abs(User.longitude - location.longitude)**2) <= radius)
TypeError: bad operand type for abs(): 'BinaryExpression'

Traceback (most recent call last):
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
    raise value
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
    raise value
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "C:\Users\Frederik\Desktop\start\app\routes.py", line 134, in explore
    profiles = User.query.filter(User.is_nearby(latitude=location.latitude, longitude=location.longitude, radius=radius))
  File "C:\Users\Frederik\Desktop\start\app\models.py", line 64, in is_nearby
    return sqrt((self.latitude - latitude)**2 + (self.longitude - longitude)**2) <= radius
TypeError: unsupported operand type(s) for ** or pow(): 'BinaryExpression' and 'int'

这是我的用户模型，它有两个与此问题相关的依赖项：

class User(UserMixin, db.Model):
    ...
    latitude = db.Column(db.Float, index=True)
    longitude = db.Column(db.Float, index=True)
    ...

为什么模型的这些属性不能应用于特定的操作数，即查询搜索中的条件内平方？在我的情况下，我该如何应对呢？

PS

非常感谢您对frost-nzcr4的评论。这意味着很多

编辑2 好的，现在根据frost-nzcr4的另一个建议，我将

is_nearest

方法更改为： （此处

func

引用了sqlalchemy导入func中的

）

而且它有效！它消除了以前的错误。。但接下来是另一个

Traceback (most recent call last):
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1244, in _execute_context
    cursor, statement, parameters, context
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\default.py", line 552, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such function: sqrt

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
    raise value
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
    raise value
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "C:\Users\Frederik\Desktop\start\app\routes.py", line 135, in explore
    profiles = User.query.filter(User.is_nearby(latitude=location.latitude, longitude=location.longitude, radius=radius)).all()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\orm\query.py", line 3161, in all
    return list(self)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\orm\query.py", line 3317, in __iter__
    return self._execute_and_instances(context)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\orm\query.py", line 3342, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 988, in execute
    return meth(self, multiparams, params)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\sql\elements.py", line 287, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1107, in _execute_clauseelement
    distilled_params,
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1248, in _execute_context
    e, statement, parameters, cursor, context
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1466, in _handle_dbapi_exception
    util.raise_from_cause(sqlalchemy_exception, exc_info)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\util\compat.py", line 383, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\util\compat.py", line 128, in reraise
    raise value.with_traceback(tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1244, in _execute_context
    cursor, statement, parameters, context
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\default.py", line 552, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such function: sqrt
[SQL: SELECT user.id AS user_id, user.name AS user_name, user.location AS user_location, user.latitude AS user_latitude, user.longitude AS user_longitude, user.username AS user_username, user.email AS user_email, user.password_hash AS user_password_hash
FROM user
WHERE sqrt(pow(user.latitude - ?, ?) + pow(user.longitude - ?, ?)) <= ?]
[parameters: (55.8125143, 2, 12.4687513, 2, '10')]
(Background on this error at: http://sqlalche.me/e/e3q8)

回溯（最近一次呼叫最后一次）：
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\base.py”，第1244行，在执行上下文中
游标、语句、参数、上下文
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\default.py”，第552行，在do\u execute中
cursor.execute（语句、参数）
sqlite3.ERROR:没有这样的函数：sqrt
上述异常是以下异常的直接原因：
回溯（最近一次呼叫最后一次）：
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第2309行，在调用中__
返回self.wsgi_应用程序（环境，启动响应）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第2295行，位于wsgi\u应用程序中
response=self.handle\u异常（e）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第1741行，位于句柄\u异常中
重放（exc_类型、exc_值、tb）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\\u compat.py”，第35行，在reraise中
增值
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第2292行，位于wsgi\u应用程序中
response=self.full\u dispatch\u request（）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第1815行，完全发送请求
rv=自身处理用户异常（e）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第1718行，在handle\u user\u异常中
重放（exc_类型、exc_值、tb）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\\u compat.py”，第35行，在reraise中
增值
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第1813行，完全发送请求
rv=自我分派请求（）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\flask\app.py”，第1799行，在调度请求中
返回self.view_函数[rule.endpoint]（**req.view_参数）
文件“C:\Users\Frederik\Desktop\start\app\routes.py”，第135行，在explore中
profiles=User.query.filter（User.is_附近（纬度=位置.纬度，经度=位置.经度，半径=半径））.all（）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\orm\query.py”，第3161行，共
返回列表（自我）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\orm\query.py”，第3317行，在__
返回self.\u执行\u和\u实例（上下文）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\orm\query.py”，第3342行，在执行和实例中
结果=conn.execute（querycontext.statement，self.\u参数）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\base.py”，执行中第988行
返回方法（自身、多线程、参数）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\sql\elements.py”，第287行，在连接上执行
返回连接。_execute_clauseelement（self、multiparams、params）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\base.py”，第1107行，在执行条款元素中
你的参数，
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\base.py”，第1248行，在执行上下文中
e、 语句、参数、游标、上下文
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\base.py”，第1466行，在(句柄)dbapi(异常)中
util.raise\u from\u cause（sqlalchemy\u异常，exc\u信息）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\util\compat.py”，第383行，位于raise\u from\u cause中
重新释放（类型（异常），异常，tb=exc\U tb，原因=原因）
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\util\compat.py”，第128行，在reraise中
通过_回溯（tb）提升值
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\base.py”，第1244行，在执行上下文中
游标、语句、参数、上下文
文件“c:\users\frederik\appdata\local\programs\python\python37\lib\site packages\sqlalchemy\engine\default.py”，lin
profiles = User.query.filter(User.is_nearby(latitude=location.latitude, longitude=location.longitude, radius=radius)).all()

Traceback (most recent call last):
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1244, in _execute_context
    cursor, statement, parameters, context
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\default.py", line 552, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such function: sqrt

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
    raise value
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\_compat.py", line 35, in reraise
    raise value
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\flask\app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "C:\Users\Frederik\Desktop\start\app\routes.py", line 135, in explore
    profiles = User.query.filter(User.is_nearby(latitude=location.latitude, longitude=location.longitude, radius=radius)).all()
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\orm\query.py", line 3161, in all
    return list(self)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\orm\query.py", line 3317, in __iter__
    return self._execute_and_instances(context)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\orm\query.py", line 3342, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 988, in execute
    return meth(self, multiparams, params)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\sql\elements.py", line 287, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1107, in _execute_clauseelement
    distilled_params,
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1248, in _execute_context
    e, statement, parameters, cursor, context
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1466, in _handle_dbapi_exception
    util.raise_from_cause(sqlalchemy_exception, exc_info)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\util\compat.py", line 383, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\util\compat.py", line 128, in reraise
    raise value.with_traceback(tb)
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\base.py", line 1244, in _execute_context
    cursor, statement, parameters, context
  File "c:\users\frederik\appdata\local\programs\python\python37\lib\site-packages\sqlalchemy\engine\default.py", line 552, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such function: sqrt
[SQL: SELECT user.id AS user_id, user.name AS user_name, user.location AS user_location, user.latitude AS user_latitude, user.longitude AS user_longitude, user.username AS user_username, user.email AS user_email, user.password_hash AS user_password_hash
FROM user
WHERE sqrt(pow(user.latitude - ?, ?) + pow(user.longitude - ?, ?)) <= ?]
[parameters: (55.8125143, 2, 12.4687513, 2, '10')]
(Background on this error at: http://sqlalche.me/e/e3q8)