txpostgres : Deferred instance has no attribute 'addCallBack'

Question

I want to use an asynchronous connection to a postgres database for inserting a realtime incomming data. I am using Twisted for the TCP communication and i am giving txpostgres a shot for the interaction with the database.I am stacked with a weird message when i try to add a callback for my asynchronous insert.Here my code:

try:
    conn = txpostgres.ConnectionPool(50,params)
    d = conn.start()
    def save_conn(c):
       self.list_cnx.append(c)
       print str(c),"Connect OK"
    def print_err(m):
       print m
   d.addCallbacks(lambda _: save_conn(conn),lambda __: print_err('Connect NO'))
except Exception as e:
    print "Cannot connect to database!!"

I am adding the refrence of the connction pool in a list for future query.

def insert_data(self,dic):
    try:
        insArRq="""INSERT INTO test_pool(date_msg, msg) VALUES ('%s','%s')"""%(dic['date'],dic['msg'])
        for c in self.list_cnx:
            def insert_finich():
                print "insert finich"
            def insert_error():
                print "insert error"
            d = c.runOperation(insArRq) # return a deferred as mentioned in the documentation
            print d # for debug
            d.addCallBack(insert_finich) # error mesage 
    except Exception as ee:
        print "Insert error :  ",ee

When i try to add a callback for the deferred returned by the runOperation this error appear:

<Deferred at 0x8d9782c waiting on Deferred at 0x8d9786c>
Insert error :   Deferred instance has no attribute 'addCallBack'

and sometimes:

<Deferred at 0x8d97a0c>
Insert error :   Deferred instance has no attribute 'addCallBack'

Help me please, i'am new to defrred concepts so i think i'am missing something.Thanks

Answer 1

The method is named addCallback; case is important.