import psycopg2


host = 'localhost'
db = 'your_db'
user = 'your_username'
password = 'your_pw'
connect_string = "dbname='%s' user='%s' host='%s' password='%s'" % (
    db, user, host, password
    )



def connect_db():
    try:
        connection = psycopg2.connect(connect_string)
    except Exception, e:
        print "Error connection to db!"
        raise
    else:
        print "Successfull connection"
    return connection