我正在尝试更新数据库模型。所以我尝试了下面的代码，
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
请参阅，我提交了一个提交但是在打印所有数据库行时未更新原始行。 request是sqlalchemy模型实例。我得到的上述代码的输出是，
<models.RequestModel object at 0x323...>
12
12
None
以下是我RequestModel的样子，
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)
我的整个文件看起来像这样，
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()
答案 0 :(得分：1)
似乎程序逻辑中存在错误：在函数calc_r_quantity_and_status中，首先处理当前请求，然后全部＆＃34;先前＆＃34;处理请求并包含当前请求。例如，给定一个公司和数量的单个购买请求的会话，在DB中有0个现有请求，采取以下路径：
@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()
由于之前sell_requests没有更新当前request：
if not sell_requests:
request.r_quantity = request.quantity
但稍后会提取所有购买请求，并且由于当前请求已经保留在数据库中，因此它也包括在内：
# 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)
这会清除r_quantity并关闭所有购买请求，包括当前的购买请求。修复很简单：要么延迟当前请求的持续时间，直到完成所有处理，要么在获取以前的购买请求时将其过滤掉。