How to update the coloumn name in a datastore using google app engine

Question

I have an entity with a coloumn name geocode which is initially null value. I want to update the value of the geocode coloumn in the datastore.

I tried using the below snippet of code but it didn't work. Please Help. Thanks in advance.

The Datastore

class doctor(db.Model):
doctorUser=db.UserProperty()
    geocode=db.GeoPtProperty()

The function to update the coloumn of doctor

def post(self):
    user=users.get_current_user()
    q=doctor.all().filter("doctorUser =",user)
    if q.count()==1:
        lat=self.request.get('lat')
        lng=self.request.get('long')
        code=str(lat)+", "+str(lng)
        q[0].geocode=code
        q[0].put()

SOLVED

Here is the change that i made and it worked!

def post(self):
    user=users.get_current_user()
    q=doctor.all().filter("doctorUser =",user)
    qo=q.get()
    if q.count()==1:
        lat=self.request.get('lat')
        lng=self.request.get('long')
        code=str(lat)+", "+str(lng)
        qo.geocode=code
        qo.put()

Answer 1

You are trying to process a query object, you need to either fetch or iterate over the query to or use get() get results. The query that you are using could return more than one result,. unless you have logic elsewhere to ensure unique values for doctorUser.

Also grab your lat/long from the request before you enter the loop.

You should also stop thinking about the datastore and your model in terms of columns names. These are attributes of entities, there are no columns in the appengine datastore.

Whilst your solution you updated your original question might work it is inefficient. For instance you get an entity then do a count() which reruns the same query. I have rewritten it to be a bit more efficient, however there are still potential problems (such as multiple records that match doctorUser = user

def post(self):
    user=users.get_current_user()

    if user:  # if user not logged in user will be None

       qo=doctor.all().filter("doctorUser =",user).fetch(10)

       if len(go) > 1:
           raise ValueError('More than one doctorUser matches')

       if go:
           lat=self.request.get('lat')
           lng=self.request.get('long')
           code=str(lat)+", "+str(lng)
           qo.geocode=code
           qo.put()