Transactions

Docs > Datastore API > Transactions

from google.appengine.ext import db

class Accumulator(db.Model):
　counter = db.IntegerProperty()
　a = Accumulator()
　a.counter = 0
　a.put()

def increment_counter(key, amount):
　obj = db.get(key)
　obj.counter += amount
　obj.put()

q = db.GqlQuery("SELECT * FROM Accumulator")
acc = q.get()
db.run_in_transaction(increment_counter,acc.key(), 5)
r = db.GqlQuery("select * from Accumulator" )

for rr in r:
　print rr.counter
----
5