Question

我是Flask和SQLAlchemy的新手，我花了很多时间试图使用Flask url（不是flask_restful）使数据库查询以JSON形式显示。

我以为我可以使用n0nSmoker/SQLAlchemy-serializer来工作。通过使用以下语法并选择我的Trade SQLAlchemy类，可以使用简单查询来工作：

trades = Trade.query.all()

我能够毫无问题地返回trades.to_dict（）。

但是，因为我需要执行group_by，所以我需要使用更灵活的db.session.query(Trade, Trade.exchange, Trade.trader.......语法，以使该方法停止工作。

我查看了其他选项，例如检查系统，但似乎超出了我的技能水平。另外，似乎_asdict（）之类的某些方法在行级别上不可用。

我有点迷茫，不知道如何进行。任何帮助将不胜感激。

编辑：请求更多代码： app.py

的顶部

from flask import Flask
from flask_restful import Resource, Api
from models import *
from flask_sqlalchemy import SQLAlchemy
from sqlathanor import FlaskBaseModel, initialize_flask_sqlathanor

app = Flask(__name__)
app.config.from_pyfile('config.py')

db = SQLAlchemy(model_class = FlaskBaseModel)
db = initialize_flask_sqlathanor(db)

class Trades(Resource):
    def get(self):
        return AllTrades()

api.add_resource(Trades,'/')


if __name__ == '__main__':
    app.run(host="0.0.0.0")

来自models.py

from app import db

class Trade(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    exchange = db.Column(db.String(255))
    trader = db.Column(db.String(255))
    symbol = db.Column(db.String(255))
    coin = db.Column(db.String(255))
    order_id = db.Column(db.String(255))
    price = db.Column(db.String(255))
    qty = db.Column(db.String(255))
    fee = db.Column(db.String(255))
    fee_currency = db.Column(db.String(255))
    order_time = db.Column(db.DateTime(timezone=False))
    side = db.Column(db.String(255))
    maker_taker = db.Column(db.String(255))


def AllTrades():
    #t = Trade
    # trades = db.session.query(
    #   t,
    #   t.exchange,
    #   t.trader,
    #   t.symbol,
    #   t.coin,
    #   db.func.sum(t.qty),
    #   db.func.sum(t.fee).label("fee"),
    #   t.fee_currency,
    #   t.order_id,
    #   t.order_time,
    #   t.maker_taker
    # ).group_by(t.order_id).all()

    trades = Trade.query.all()
    trades = trades.to_json()

    return trades

完整堆栈跟踪

    Traceback (most recent call last):
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1997, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1985, in wsgi_app
    response = self.handle_exception(e)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_restful/__init__.py", line 273, in error_router
    return original_handler(e)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1540, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/_compat.py", line 32, in reraise
    raise value.with_traceback(tb)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1614, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_restful/__init__.py", line 273, in error_router
    return original_handler(e)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1517, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/_compat.py", line 32, in reraise
    raise value.with_traceback(tb)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1612, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/app.py", line 1598, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_restful/__init__.py", line 480, in wrapper
    resp = resource(*args, **kwargs)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask/views.py", line 84, in view
    return self.dispatch_request(*args, **kwargs)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_restful/__init__.py", line 595, in dispatch_request
    resp = meth(*args, **kwargs)
  File "/Users/foo/Sites/Reporting_dev/app.py", line 18, in get
    return AllTrades()
  File "/Users/foo/Sites/Reporting_dev/models.py", line 42, in AllTrades
    trades = Trade.query.all()
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py", line 514, in __get__
    return type.query_class(mapper, session=self.sa.session())
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/sqlalchemy/orm/scoping.py", line 74, in __call__
    return self.registry()
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/sqlalchemy/util/_collections.py", line 1001, in __call__
    return self.registry.setdefault(key, self.createfunc())
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2939, in __call__
    return self.class_(**local_kw)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py", line 143, in __init__
    bind = options.pop('bind', None) or db.engine
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py", line 877, in engine
    return self.get_engine()
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py", line 887, in get_engine
    state = get_state(app)
  File "/Users/foo/anaconda3/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py", line 570, in get_state
    'The sqlalchemy extension was not registered to the current ' \
AssertionError: The sqlalchemy extension was not registered to the current application.  Please make sure to call init_app() first.

Answer 1

我建议您看看我在一两周前发布的名为SQLAthanor的新图书馆。

它为SQLAlchemy模型添加了简单的序列化支持，并且如果您还使用Flask-SQLAlchemy，它也可以与它无缝地协同工作。

基本上，它的工作方式是这样的：

您可以（大概）已经定义了Trade模型。唯一的区别是您从SQLAthanor而不是从SQLAlchemy（或Flask-SQLAlchemy）导入declarative_base或基本模型。
您可以在定义模型时配置序列化规则。基本上，您可以说“当我将交易序列化为JSON时，包括属性X，Y和Z，但不包括P，D和Q”。
执行查询，但是通常会执行。据推测，您将获得Trade个实例的列表。现在，您可以通过调用<instance>.to_json()将每个实例序列化为JSON。

值得一提的是SQLAthanor：

支持与JSON，CSV，YAML和Python dict之间的序列化和反序列化
支持Column属性，关系，混合属性，关联代理和常规Python @properties的序列化/反序列化
支持自定义的前后处理功能，用于在属性级别进行序列化/反序列化（用于验证或强制转换）
支持在属性级别为特定格式启用/禁用序列化和反序列化（例如，接受入站密码，但从不包括入站密码）

可能值得一看。这里是（希望全面）文档的链接：http://sqlathanor.readthedocs.io/en/latest/

希望这会有所帮助，如果您有疑问或需要帮助以使其正常运行，请告诉我（或使用标签sqlathanor向SO提问）

Flask + SQLAlchemy结果转换为JSON

1 个答案: