Question

This line of code:

contract = Contract.get_by_id(contract_id)

From this block:

class MainHandler(webapp2.RequestHandler):
    def get(self):     
        contract_id = self.request.get("contract_id")
        if contract_id is None:
            contract = db.GqlQuery("SELECT * FROM Contract ORDER BY date DESC").get()
            if contract == None:
                numBook = 1
                numInitialPage = 1
                numFinalPage = 1            
        else:
            contract = Contract.get_by_id(contract_id)

template_values = {"numBook":numBook,
                           "numInitialPage":numInitialPage,
                           "numFinalPage":numFinalPage}
        template = jinja_environment.get_template('index.html')
        self.response.out.write(template.render(template_values))

Is producing this error:

     File "C:\Program Files (x86)\Google\google_appengine\lib\webapp2\webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "C:\Users\Py\Desktop\contract\main.py", line 277, in get
        contract_id = self.request.get("contract_id")
  File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\db\__init__.py", line 1292, in get_by_id
    ids, multiple = datastore.NormalizeAndTypeCheck(ids, (int, long))
  File "C:\Program Files (x86)\Google\google_appengine\google\appengine\api\datastore.py", line 139, in NormalizeAndTypeCheck
    (types, arg, typename(arg)))
BadArgumentError: Expected an instance or iterable of (<type 'int'>, <type 'long'>); received  (a str).

My goal is: if a value was passed through variable contract_id when other handler redirect to MainHandler, MainHandler should use it. But if MainHandler is being used for the first time, then contract_id value should be None and the program should to another thing. But this isn’t happening. When MainHandler is called, it interpret ‘contract_id’ (from self.request.get("contract_id")) as a string value. How to fix that and achieve my goal?

Answer 1

What the error is telling you is that it expected an int or a list of int. This is consistent with the docs. So you will need first to convert contract_id to an int.

...
else:
  contract = Contract.get_by_id(int(contract_id))

Also you need to change how you check if the contract_id was passed. The self.request.get method returns an empty string when the value is not defined. See http://webapp-improved.appspot.com/api/webapp2.html#webapp2.Request.get.

So you have to alternatives here:

contract_id = self.request.get("contract_id")
if not contract_id:

or

contract_id = self.request.get("contract_id", None)
if contract_id is None: