from urlib.request import urlopen
import json
import psycopg2
import psycopg2.extras

try:
    db = psycopg2.connect("dbname=myapp user=postgres password=postgres")
    cursor = db.cursor()
    query = "select city from myapp"
    cursor.execute(query)
    data = cursor.fetchall()
    for row in data:
        print (row)
    db.close()