How to check if entity exist in gae datastore?

Question

I need to check datastore if entity kind "Kayit" exist to create new . my db.model class:

class Kayit(db.Model):
    url=db.StringProperty()
    date = db.DateTimeProperty(auto_now_add=True)

currently using this to check but it doesnt seem elegant

class MainPage(webapp2.RequestHandler):
    def get(self):
        r_name="none"               
        q=db.Query(Kayit)    
        try:
            self.response.write(q[0].url)
        except:
            kay=Kayit(parent=_DefterKey(r_name),key_name='alibaba')
            kay.url="some url"                
            kay.put()

I guess we get the parent key with db.Key.from_path('Kayit', 1) . how can I use to check if it has entities?

Is there a reason you **must** use old crufty `db` rather than the vastly preferred, newer `ndb`? I'm so rusty on `db` that I'd need a long refresh cycle to help w/that -- I've used nothing but `ndb` for so many years! — Alex Martelli, Feb 06 '15 at 03:11
@AlexMartelli as you can guess from my questions to you, because I'm totaly a newbie :) — St3114, Feb 06 '15 at 20:32

score 1 · Accepted Answer · edited May 23 '17 at 12:24

The was answered by:

How to query parent entity from child entity in Google App Engine (Python) NDB/Datastore?

documented in in the cloud API:

https://cloud.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/Entity

...and is shown in the python "Guestbook" google example:

https://cloud.google.com/appengine/docs/python/gettingstartedpython27/usingdatastore

Look at the stanza that goes:

 greetings_query = Greeting.query(
        ancestor=guestbook_key(guestbook_name)).order(-Greeting.date)
 greetings = greetings_query.fetch(10)

How to check if entity exist in gae datastore?

1 Answers1