Python中的类型-Google Appengine

Question

Getting a bit peeved now;

I have a model and a class thats just storing a get request in the database; basic tracking.

class SearchRec(db.Model):
  WebSite = db.StringProperty()#required=True
  WebPage = db.StringProperty()
  CountryNM = db.StringProperty()
  PrefMailing = db.BooleanProperty()
  DateStamp = db.DateTimeProperty(auto_now_add=True)
  IP = db.StringProperty()

class AddSearch(webapp.RequestHandler):
  def get(self):
    searchRec = SearchRec()

    searchRec.WebSite = self.request.get('WEBSITE')
    searchRec.WebPage = self.request.get('WEBPAGE')
    searchRec.CountryNM = self.request.get('COUNTRY')
    searchRec.PrefMailing = bool(self.request.get('MAIL'))
    searchRec.IP = self.request.get('IP')

Bool has my biscuit; I thought that setting bool(self.reque....) would set the type of the string but no matter what I pass it it still stores it as TRUE in the database. I had the same issue with using required=True on strings for the model; the damn thing kept saying that nothing was being passed... but it had.

Ta

Answer 1

You've added a lot of layers of complication to understanding what the bool() build-in function does. Why don't you test it out directly on the command-line, before embedding it deep in your google app engine code.

What you'd discover is that the bool() function uses python's truth values:

http://docs.python.org/library/stdtypes.html#truth-value-testing

The following values are considered false:

 * None * False * zero of any numeric type, for example, 0, 0L, 0.0, 0j. * any empty sequence, for example, '', (), []. * any empty mapping, for example, {}. * instances of user-defined classes, if the class defines a `__nonzero__()` or `__len__()` method, when that method returns the integer zero or bool value False. [1] 

All other values are considered true — so objects of many types are always true.

In particular - any non-empty string is True .

Answer 2

Bool has my biscuit; I thought that setting bool(self.reque....) would set the type of the string but no matter what I pass it it still stores it as TRUE in the database.

Well, what's the value of self.request.get('MAIL') ? If it's anything other than an empty string or None , bool will see it as True .

I had the same issue with using required=True on strings for the model; the damn thing kept saying that nothing was being passed... but it had.

If you set a property to required=True , then you must pass it to the model's constructor. So, if WebSite is a required property, you need to construct your searchRec like so:

searchRec = SearchRec(WebSite=self.request.get('WEBSITE'))