label='ave_number'

sql_cmd=u"""UPDATE rpt.so_form2_test_noquotes SET %s=%s WHERE channel_id=%s and report_id=%s and load_date=current_date;"""
                            sql_params=(label, e[u"label"],channel_id,report_id,)
                            calldb(conn, sql_cmd, sql_params)

def calldb( db, sql_cmd, sql_params):   # invoke backend function that is a INSERT/UPDATE statement
    try:
        cur = db.cursor()  # use standard cursor as return is likely void
        print 'Executing sql cmd "{0}"'.format(cur.mogrify(sql_cmd, sql_params))
        cur.execute(sql_cmd, sql_params)
        return   # execute returns None expected

    except Exception as e:
        print u'Error ', e
        raise

from psycopg2.extensions import AsIs
import psycopg2


def calldb( db, sql_cmd, sql_params):   # invoke backend function that is a INSERT/UPDATE statement
    try:
        cur = db.cursor()  # use standard cursor as return is likely void
        print 'Executing sql cmd "{0}"'.format(cur.mogrify(sql_cmd, sql_params))
        cur.execute(sql_cmd, sql_params)
        return   # execute returns None expected

    except Exception as e:
        print u'Error ', e
        raise


conn = psycopg2.connect(host='localhost', port=5432, user='xxxxxxx', password='xxxxxx')

label='ave_number'

e={u'label':'test_label'}
channel_id=1
report_id=1

sql_cmd=u"""UPDATE rpt.so_form2_test_noquotes SET %s=%s WHERE channel_id=%s and report_id=%s and load_date=current_date;"""
sql_params=(AsIs(label), e[u"label"],channel_id,report_id,)
calldb(conn, sql_cmd, sql_params)

Executing sql cmd "UPDATE rpt.so_form2_test_noquotes SET ave_number='test_label' WHERE channel_id=1 and report_id=1 and load_date=current_date;"