sqlalchemy не удалось обновить мою модель

Question

Я пытаюсь обновить модель db. Так что я попытался код ниже,

if not sell_requests: 
    request.r_quantity = request.quantity 
    request.status = StatusEnum.opened 

    print request 
    print request.quantity 
    print request.r_quantity 
    con = session.commit() 
    print con 

Посмотреть, я сделал коммит, но оригинальная строка не обновляется при печати всех строк БД. request - экземпляр модели sqlalchemy. Вывод я для приведенного выше кода,

<models.RequestModel object at 0x323...> 
12 
12 
None 

Вот как мой RequestModel выглядит,

class RequestModel(Base): 
    __tablename__ = 'request' 
    # Here we define columns for the table address. 
    # Notice that each column is also a normal Python instance attribute. 
    id = Column(Integer, primary_key=True) 
    type = Column(Integer) 
    company = Column(Integer, ForeignKey('company.id')) 
    quantity = Column(Integer) 
    r_quantity = Column(Integer, default=0) 
    status = Column(Integer, default=0) 

Мой весь файл выглядит так,

from sqlalchemy.ext.declarative import declarative_base 
from sqlalchemy import Column, Integer, String 
from sqlalchemy.ext.declarative import declarative_base 

# model base class 
from sqlalchemy import create_engine 
from sqlalchemy.orm import sessionmaker 

from models import CompanyModel, RequestModel 


Base = declarative_base() 
engine = create_engine('sqlite:///sqlalchemy_test.db') 
# Bind the engine to the metadata of the Base class so that the 
# declaratives can be accessed through a DBSession instance 
Base.metadata.bind = engine 

DBSession = sessionmaker(bind=engine) 
session = DBSession() 

class Side: 
    """ 
    ENUM class forstoring the request type 
    """ 

    BUY = 1 
    SELL = 2 

    @classmethod 
    def get_type_by_value(cls, value): 
     return next(k for k, v in cls.__dict__.items() if v == value) 


class StatusEnum: 
    opened = 1 
    closed = 0 

    @classmethod 
    def get_type_by_value(cls, value): 
     return next(k for k, v in cls.__dict__.items() if v == value) 


class RequestHelper: 
    @classmethod 
    def get_previous_buy_requests(cls, company): 
     return session.query(RequestModel).filter(RequestModel.company == company.id, RequestModel.type == Side.BUY).all() 

    @classmethod 
    def get_previous_sell_requests(cls, company): 
     return session.query(RequestModel).filter(RequestModel.company == company.id, RequestModel.type == Side.SELL).all() 

    @classmethod 
    def calc_r_quantity_and_status(cls, request): 
     company = Company.get_by_id(request.company) 

     if request.type == Side.BUY: 

      # add buy quantity to the company's buy quantity 
      company.buy_quantity += request.quantity 

      sell_requests = cls.get_previous_sell_requests(company) 

      # if not previous sell requests then r_quantity is same as quantity 
      if not sell_requests: 
       request.r_quantity = request.quantity 
       request.status = StatusEnum.opened 

       # print request 
       # print request.quantity 
       # print request.r_quantity 
       session.commit() 


       # close the previous buy request if opened 
       prev_buy_requests = cls.get_previous_buy_requests(company) 
       for req in prev_buy_requests: 
        if req.status == StatusEnum.opened: 
         req.r_quantity = 0 
         req.status = StatusEnum.closed 
         # session.add(req) 

       session.commit() 

      # any sell requests 
      else: 
       for sell in sell_requests: 
        if sell.status == StatusEnum.opened: 

         # check whether the sell quan is greater than current buy request quantity 
         # if greater then add the current buy req quantity with the existsing buy quantity else 
         if sell.r_quantity < request.quantity: 
          company.buy_quantity += request.quantity 
          request.r_quantity = request.quantity - sell.r_quantity 
          request.status = StatusEnum.opened 
          sell.r_quantity = 0 
          sell.status = StatusEnum.closed 
         else: 
          sell.r_quantity -= request.quantity 
          company.sell_quantity = sell.r_quantity 
          request.r_quantity = 0 
          request.status = StatusEnum.closed 
         # session.add(request) 
         # session.add(sell) 

       session.commit() 

     elif request.type == Side.SELL: 
      # add sell quantity to the company's sell quantity 
      company.sell_quantity += request.quantity 

      buy_requests = cls.get_previous_buy_requests(company) 

      if not buy_requests: 
       request.r_quantity = request.quantity 
       request.status = StatusEnum.opened 
       # session.add(request) 

       prev_sell_requests = cls.get_previous_sell_requests(company) 
       for req in prev_sell_requests: 
        if req.status == StatusEnum.opened: 
         req.r_quantity = 0 
         req.status = StatusEnum.closed 
         # session.add(req) 

       session.commit() 

      else: 
       for buy in buy_requests: 
        if buy.status == StatusEnum.opened: 
         if buy.r_quantity > request.quantity: 
          company.buy_quantity = buy.r_quantity - request.quantity 
          request.r_quantity = 0 
          buy.r_quantity = company.buy_quantity 

          request.status = StatusEnum.closed 

         else: 
          request.r_quantity = request.quantity - buy.r_quantity 
          buy.r_quantity = 0 
          buy.status = StatusEnum.closed 
          request.status = StatusEnum.opened 
         # session.add(request) 
         # session.add(buy) 
       session.commit() 



class Company(object): 
    @classmethod 
    def get_or_create_company(cls, name): 

     company = session.query(CompanyModel).filter(CompanyModel.name == name).all() 
     if not company: 
      company = CompanyModel(name=name, buy_quantity=0, sell_quantity=0) 
      session.add(company) 
      session.commit() 
      return company 

     return company[0] 

    @classmethod 
    def get_by_id(cls, id): 
     com = session.query(CompanyModel).filter(CompanyModel.id == id) 
     if com: 
      return com.one() 
     return None 





class Requests(object): 
    template_lines = [] 
    template_header = 'Side |  Company | Quantity | RemaingQty | Status' 
    template_line_format = '{} | {} | {}  | {} | {}' 



    @classmethod 
    def do_validation(cls, request_type, company, quantity): 
     if request_type.upper() not in dir(Side): 
      raise ValueError('Request type must be either buy or sell') 

     if not company: 
      raise ValueError('You must enter the company name') 

     if not quantity or not quantity.isdigit(): 
      raise ValueError('You should enter integer value for quantity field') 

    @classmethod 
    def create_request(cls, request_type, company, quantity): 
     new_request = RequestModel(type=request_type, company=company.id, quantity=quantity, r_quantity=0, status=0) 
     session.add(new_request) 
     session.commit() 
     new_request.r_quantity = 2 
     session.commit() 

     print new_request.r_quantity 

     return new_request 



    @classmethod 
    def generate_output(cls): 
     requests = session.query(RequestModel).all() 
     for ins in requests: 
      print ins.r_quantity 
      Requests.template_lines.append(Requests.template_line_format.format(Side.get_type_by_value(ins.type), Company.get_by_id(ins.company).name, ins.quantity, ins.r_quantity, StatusEnum.get_type_by_value(ins.status))) 

     print Requests.template_header 
     print '\r\n'.join(Requests.template_lines) 


def main(): 
    # truncating models 
    session.query(CompanyModel).delete() 
    session.query(RequestModel).delete() 


    while True: 
     side = raw_input('Enter the side (buy/sell):\n') 
     company = raw_input('Enter the company:\n') 
     quantity = raw_input('Enter the quantity:\n') 

     com = Company.get_or_create_company(company) 

     # store the order request in db 
     try: 
      Requests.do_validation(side, com, quantity) 
     except ValueError: 
      continue 

     new_request = Requests.create_request(getattr(Side, side.upper()), com, quantity) 
     RequestHelper.calc_r_quantity_and_status(new_request) 


     out = raw_input('Do you want to continue (Y/n)?\n') 
     if out.lower() == 'n': 
      Requests.generate_output() 

      # truncating models 
      session.query(CompanyModel).delete() 
      session.query(RequestModel).delete() 

      break 

     continue 



if __name__ == '__main__': 
    main() 

Answer 1

Казалось бы, что есть ошибка в логике программы: в функции calc_r_quantity_and_status текущий запрос сначала обрабатывается, но затем обрабатываются все «предыдущие» запросы и включается текущий запрос. Для примера, приведенного сеанс одного запроса на покупке какой-либо компании и количества, с 0 существующих запросами в БДЕ, следующий путь берется:

@classmethod 
def calc_r_quantity_and_status(cls, request): 
    company = Company.get_by_id(request.company) 

    if request.type == Side.BUY: 

     # add buy quantity to the company's buy quantity 
     company.buy_quantity += request.quantity 

     sell_requests = cls.get_previous_sell_requests(company) 

     # if not previous sell requests then r_quantity is same as quantity 
     if not sell_requests: 
      request.r_quantity = request.quantity 
      request.status = StatusEnum.opened 

      # print request 
      # print request.quantity 
      # print request.r_quantity 
      session.commit() 


      # close the previous buy request if opened 
      prev_buy_requests = cls.get_previous_buy_requests(company) 
      for req in prev_buy_requests: 
       if req.status == StatusEnum.opened: 
        req.r_quantity = 0 
        req.status = StatusEnum.closed 
        # session.add(req) 

      session.commit() 

не Поскольку там нет предыдущего sell_requests тока request обновляется:

 if not sell_requests: 
      request.r_quantity = request.quantity 

Но позже все покупают запросы извлекаются и так как текущий запрос уже сохраняется в базе данных, она также включена:

  # close the previous buy request if opened 
      prev_buy_requests = cls.get_previous_buy_requests(company) 
      for req in prev_buy_requests: 
       if req.status == StatusEnum.opened: 
        req.r_quantity = 0 
        req.status = StatusEnum.closed 
        # session.add(req) 

Это нулевое значение r_quantity и закрывает все запросы на покупку, включая текущий. Исправление является простым: либо отложить сохранение текущего запроса до завершения всей обработки, либо отфильтровать его при получении предыдущих запросов на покупку.