Thread: python async with psycopg2
I am trying to listen to multiple channels thru pg_notify mechanism.
--
select pg_notify('mychan0',foo');
select pg_notify('mychan'1,'bar');
In python I have something like this
import select,time
import psycopg2
import psycopg2.extensions
from psycopg2.extras import wait_select
DSN="dbname=mydb user=user host=localhost"
def main():
conn = psycopg2.connect(DSN,async_=True)
wait_select(conn)
curs = conn.cursor()
curs.execute("LISTEN mychan0;")
import psycopg2
import psycopg2.extensions
from psycopg2.extras import wait_select
DSN="dbname=mydb user=user host=localhost"
def main():
conn = psycopg2.connect(DSN,async_=True)
wait_select(conn)
curs = conn.cursor()
curs.execute("LISTEN mychan0;")
#curs.execute("LISTEN mychan1;") #fails!
wait_select(conn)
while True:
wait_select(conn)
while conn.notifies:
print("Notify: %s"%conn.notifies.pop().payload)
time.sleep(1)
conn.close()
wait_select(conn)
while True:
wait_select(conn)
while conn.notifies:
print("Notify: %s"%conn.notifies.pop().payload)
time.sleep(1)
conn.close()
I keep getting
psycopg2.ProgrammingError: execute cannot be used while an asynchronous query is underway
I prefer to stick with psycopg2 library instead of a wrapper.
What am I doing wrong?
--- Get your facts first, then you can distort them as you please.--
On Fri, 17 Jul 2020 at 20:44, Rita <rmorgan466@gmail.com> wrote:>
> curs = conn.cursor()
> curs.execute("LISTEN mychan0;")
> #curs.execute("LISTEN mychan1;") #fails!
> wait_select(conn)
Maybe you have to wait_select after each execute.
This example could be helpful.
https://www.psycopg.org/docs/advanced.html#asynchronous-notifications
Note that you don't need an async connection to receive notification:
a sync one, as long as is in autocommit and you are using an I/O
completion function to wait for readiness, works as well.
-- Daniele