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
