[code]

....

   'current_stock': fields.function(_get_current_stock, type='char', string='Currently in stock'),
....

 #getting quants from stock.quant to put into field 'current_stock'

def _get_current_stock(self, cr, uid, ids, field_name, arg, context=None):

res = []

in_stock = 0

tot_sold = 0

product_id = 0

for obj in self.browse(cr, uid, ids, context=context):

#first query read data about product sold
cr.execute(""" select sum(qty) from stock_quant where product_id = %s and location_id = 7;""" %(obj.product_id.id))
tot_sold = cr.fetchall()

#second query read data adout products left in stock
cr.execute(""" select sum(qty) from stock_quant where product_id = %s and location_id != 7;""" %(obj.product_id.id))
in_stock = cr.fetchall()

res = in_stock[0]    <= once i add this, everything stops and getting error, of course if I remove it got no error but also current_stock stays empty because res = ''

# I can print value of tot_sold and in_stock
print '|| Total sell: ', tot_sold[0], ' Left in stock: ',in_stock[0]

return res

 Getting this error and don't know how to extract data from res and populate with related field 'current_stock'

new_values = dict(values)

TypeError: cannot convert dictionary update sequence element #0 to a sequence