的Python GAE datastoreAttributeError：“NoneType”对象没有属性

Question

运行代码波纹管，我得到这个错误：

Traceback (most recent call last): 
    File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 1536, in __call__ 
    rv = self.handle_exception(request, response, e) 
    File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 1530, in __call__ 
    rv = self.router.dispatch(request, response) 
    File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 1278, in default_dispatcher 
    return route.handler_adapter(request, response) 
    File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 1102, in __call__ 
    return handler.dispatch() 
    File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 572, in dispatch 
    return self.handle_exception(e, self.app.debug) 
    File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 570, in dispatch 
    return method(*args, **kwargs) 
    File "C:\Users\CG\Documents\ud\contract\main.py", line 81, in get 
    numBook = contract.book_number 
AttributeError: 'NoneType' object has no attribute 'book_number' 

因为我把在BD合同初始行（如sugested here和其他类似的问题）：

first_query = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC") 
       if first_query is None: # Puting something in db if it's empty 
        first_record = Contract(book_number = 1, initial_page = 1, final_page = 1) 
        first_record.put() 

我也做一个测试，以验证该查询返回无：

first_query = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC") 
    if first_query is None: # Puting something in db if it's empty 
     first_record = Contract(book_number = 1, initial_page = 1, final_page = 1) 
     first_record.put() 
    else:   
     numBook = 0 
     numInitialPage = 0 
     numFinalPage = 0 

当我打印： Q = db.GqlQuery（ “SELECT * FROM合同ORDER BY日期DESC”）

我得到这个：

当我打印：

contract = q.get() 

我得到没有

如何解决make put（）的工作？

# -*- coding: utf-8 -*- 
# -*- coding: utf-8 -*- 
#!/usr/bin/env python 
# 
# Copyright 2007 Google Inc. 
# 
# Licensed under the Apache License, Version 2.0 (the "License"); 
# you may not use this file except in compliance with the License. 
# You may obtain a copy of the License at 
# 
#  http://www.apache.org/licenses/LICENSE-2.0 
# 
# Unless required by applicable law or agreed to in writing, software 
# distributed under the License is distributed on an "AS IS" BASIS, 
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
# See the License for the specific language governing permissions and 
# limitations under the License. 
# 

import os 

import webapp2 

import jinja2 

jinja_environment = jinja2.Environment(autoescape=True, 
    loader=jinja2.FileSystemLoader(os.path.join(os.path.dirname(__file__), 'templates'))) 

import re 

from google.appengine.ext import db 

USER_RE = re.compile(r"^[a-zA-Z0-9_ -]{3,20}$") 
def valid_person(person): 
    return USER_RE.match(person) 

PASS_RE = re.compile(r"^.{3,20}$") 
def valid_SSN(SSN): 
    return PASS_RE.match(SSN) 

EMAIL_RE = re.compile(r"^[\S]+@[\S]+\.[\S]+$") 
def valid_email(email): 
    return EMAIL_RE.match(email) 

import time 

import datetime 


def dateToday(): 
    today = datetime.datetime.today() 
    todayDay = str(today.day) 
    todayMonth = str(today.month) 
    monthExt = {'1':' January ', '2':'February', '3':' March ', '4':'April', '5':'May', '6':'June', '7':' July ', '8':'August', '9':'September', '10':'October', '11':'November ', '12':'December'} 
    todayYear = str(today.year) 
    return(todayDay + ' of ' + monthExt[todayMonth] + ' of ' + todayYear) 

class Contract(db.Model): 
    book_number = db.IntegerProperty(required = True) 
    initial_page = db.IntegerProperty(required = True) 
    final_page = db.IntegerProperty(required = True) 
    date = db.DateTimeProperty(auto_now_add=True) 

class MainHandler(webapp2.RequestHandler): 
    def get(self): 
     first_query = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC") 
      if first_query is None: # Puting something in db if it's empty 
       first_record = Contract(book_number = 1, initial_page = 1, final_page = 1) 
       first_record.put() 
     q = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC") 
     contract = q.get() # return only the first entity 
     numBook = contract.book_number 
     numInitialPage = contract.initial_page 
     numFinalPage = contract.final_page 
     template_values = {"person": "", 
             "nacionality": "", 
             "SSN": "", 
             "driverLicense": "", 
             "email":"", 
             "person_error": "", 
             "SSN_error": "", 
             "driverLicense_error": "", 
             "address": "", 
             "email_error": "", 
             "numBook": numBook, 
             "numInitialPage": numInitialPage, 
             "numFinalPage": numFinalPage, 
             } 
     template = jinja_environment.get_template('index.html') 
     self.response.out.write(template.render(template_values)) 

    def post(self): 
     person_name = self.request.get("person") 
     user_nacionality = self.request.get('nacionality') 
     user_profession = self.request.get('profession') 
     user_maritalStatus = self.request.get('maritalStatus') 
     user_SSN = self.request.get('SSN') 
     user_email = self.request.get('email') 
     user_driverLicense = self.request.get('driverLicense') 
     person_error = "" 
     SSN_error = "" 
     driverLicense_error = "" 
     geted_email_error = "" 
     address = self.request.get('address') 
     contractType = self.request.get("contractType") 
     owner = self.request.get("owner") 
     witness = self.request.get("witness") 
     numBook = self.request.get("numBook") 
     numInitialPage = self.request.get("numInitialPage") 
     numFinalPage = self.request.get("numFinalPage") 

     if (person_name and valid_person(person_name)) and (user_SSN and valid_SSN(user_SSN)) and ((not user_email) or (user_email and valid_email(user_email))): 
      a = Person(firstName = person_name, 
            nacionality = user_nacionality, 
            maritalStatus = user_maritalStatus, 
            profession = user_profession, 
            SSN = int(user_SSN), 
            driverLicense = int(user_driverLicense) 
            #address = user_address 
            ) 
      a.put() 
      self.redirect('/your_contract?person=%s&nacionality=%s&profession=%s&maritalStatus=%s&SSN=%s&driverLicense=%s&email=%s&witness=%s&owner=%s&contractType=%s&address=%s&numBook=%s&numInitialPage=%s&numFinalPage=%s' % (person_name, user_nacionality, user_profession, user_maritalStatus, user_SSN, user_driverLicense, user_email, 
witness, owner, contractType, address, numBook, numInitialPage, numFinalPage)) 

     else: 
      if not person_name or not valid_person(person_name): 
       person_error = "Oh no!!! this person name isn't valid!" 
      if not user_SSN or not valid_SSN(user_SSN): 
       SSN_error = "Oh no!!! SSN isn't valid!" 
      if user_email and not valid_email(user_email): 
       geted_email_error = "Oh no!!! e-mail isn't valid!" 
      template_values = {"person": person_name, 
           "nacionality": user_nacionality, 
           "maritalStatus": user_maritalStatus, 
           "profession": user_profession, 
           "SSN": user_SSN, 
           "driverLicense": user_driverLicense, 
           "email": user_email, 
           "person_error": person_error, 
           "SSN_error": SSN_error, 
           "driverLicense_error": user_driverLicense, 
           "address": address, 
           "email_error": geted_email_error} 
      template = jinja_environment.get_template('index.html') 
      self.response.out.write(template.render(template_values)) 

class your_contractHandler(webapp2.RequestHandler): 
    def get(self): 
     geted_person_name = self.request.get('person') 
     geted_user_nacionality = self.request.get("nacionality") 
     geted_user_profession = self.request.get("profession") 
     geted_user_maritalStatus = self.request.get("maritalStatus") 
     geted_user_SSN = self.request.get('SSN') 
     geted_user_email = self.request.get('email') 
     geted_user_driverLicense = self.request.get('driverLicense') 
     geted_person_error = "" 
     geted_SSN_error = "" 
     geted_driverLicense_error = "" 
     geted_address = self.request.get('address') 
     geted_owner = self.request.get("owner") 
     geted_witness = self.request.get("witness") 
     geted_contractType = self.request.get("contractType") 
     geted_dateToday = dateToday() 
     your_contract = jinja_environment.get_template('your_contract.html') 
     geted_numBook = self.request.get('numBook') 
     geted_numInitialPage = self.request.get('numInitialPage') 
     geted_numFinalPage = self.request.get('numFinalPage') 

     contract = Contract(book_number = geted_numBook, initial_page = geted_numInitialPage, final_page = geted_numFinalPage) 
     contract.put() 

     your_contract_values = {"person":geted_person_name, 
           "nacionality":geted_user_nacionality, 
           "maritalStatus": geted_user_maritalStatus, 
           "profession": geted_user_profession, 
           "SSN":geted_user_SSN, 
           "driverLicense":geted_user_driverLicense, 
           "address":geted_address, 
           "email":geted_user_email, 
           "contractType":geted_contractType, 
           "dateContract":geted_dateToday, 
           "numBook":geted_numBook, 
           "numInitialPage":geted_numInitialPage, 
           "numFinalPage":geted_numInitialPage, 
           } 
     template = jinja_environment.get_template('index.html') 
     self.response.out.write(your_contract.render(your_contract_values)) 


class Contract(db.Model): 
    book_number = db.IntegerProperty(required = True) 
    initial_page = db.IntegerProperty(required = True) 
    final_page = db.IntegerProperty(required = True) 
    date = db.DateTimeProperty(auto_now_add=True) 


app = webapp2.WSGIApplication([('/', MainHandler), ('/your_contract', your_contractHandler)], 
           debug=True) 

Answer 1

试试这个：

first_query = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC").get() 

你必须使用的get（）选择最后一条记录（而不是查询对象）。所以，代码将在if块内运行。

Answer 2

可能是因为该查询返回的什么都没有，试试这个：

q = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC") 
contract = q.get() # return only the first entity 
if contract is not None: 
    numBook = contract.book_number 
else: 
    print('contract is None')