Complex transactions without using plPgSQL Functions. It is possible?

Hi,

I'm writing a web application that uses PostgreSQL and I need to do
some operations where I read/write to 3 tables in the same
transaction. To do this I need to store the values of variables and
I'm not sure if it is possible to do this without using plPgSQL.

[code]
SELECT count(email) INTO vCONTA_HIST FROM am_newsletter_hist_alter
WHERE email = pEMAIL AND id_website_recolha = pID_WEBSITE_RECOLHA;

IF vCONTA_HIST = 0 THEN
vNUM_ALTER := 1;
ELSE
SELECT MAX(num_alter) INTO vNUM_ALTER_ACT FROM am_newsletter_hist_alter
WHERE email = pEMAIL AND id_website_recolha = pID_WEBSITE_RECOLHA LIMIT 1;
vNUM_ALTER := vNUM_ALTER_ACT + 1;
END IF;
[/code]

This is the plPgSQL code that I need to write in Python. It is
possible to do this without using PlPgSQL?

Best Regards,