Iterate over GQL query fields

Question

I am trying to implement an 'Edit' function for entities in a google app engine datastore. So if a key is specified for an datastore entity I would like to fill a form with values associated with this key. If no key is specified, then these values will be pulled from the previous form post attempt. While I am able to loop through the self.request fields with self.request.arguments(), I do not know how to do this with the datastore (db.get(key)) object.

So please let me know if this is possible, or even if I am way off with my gae form processing.

class ItemsPage(webapp2.RequestHandler):
    def __init__(self, *args, **kwargs):
        super(ItemsPage, self).__init__(*args, **kwargs)
        self.formerrors = dict()
        self.formdata = dict()

    def get(self):

        if self.request.get('key'):
            # Key specified, get field values from db store
            key = self.request.get('key')
            item = db.get(key)
            for field in item.arguments():  # THIS DOES NOT WORK
                self.formdata[field] = item.field
        else:
            # No key specified, use the self.request values
            for field in self.request.arguments(): # THIS DOES WORK
                self.formdata[field] = self.request.get(field)

        # render the template with the formdata 
        template_values = {
                           'formerrors': self.formerrors,
                           'formdata': self.formdata # Use formdata to populate form fields
                           }
         template = JINJA_ENVIRONMENT.get_template(
                           'templates/items.html'
                           )
         self.response.write(template.render(template_values))

    def post(self):
        if self.validateSortForm():
            # Form input is valid, do some processing and then put into datastore
            item = itemDatstore()
            item.put()
            self.redirect('/')
        else():
            # Form input was not valid, redisplay the form
            self.get()

Thank you

Answer 1

Thanks for the help marcadian, that put me on the right path. As the docs say

Model.properties ()

Returns a dictionary of all of the properties defined for this model class.

So I call properties() on a db.Model object from google.appengine.ext and get a dict of all the properties that I can iterate through.

if self.request.get('key'):
    # Key specified, get field values from db store
    key = self.request.get('key')
    sort = db.get(key)
    for field in ItemDB.properties():
        self.formdata[field] = getattr(sort, field)