#!/usr/bin/python

import psycopg2

conn = psycopg2.connect(database="test", user="postgres", password="usuario", host="127.0.0.1", port="5432")
print "Opened database successfully"

cur = conn.cursor()

cur.execute("UPDATE PERSONA set nombre = 'ANA' where ID=3")
conn.commit()
# ^ AQUI ^ ^ el paréntesis es importante!
print "Total number of rows updated :", cur.rowcount

cur.execute("SELECT id, nombre from PERSONA")
rows = cur.fetchall()
for row in rows:
   print "ID = ", row[0]
   print "NOMBRE = ", row[1]

print "OPERACION REALIZADA";
conn.close()