I added a monetary field (x_studio_total_price) to the stock moves of a delivery order, to show the prices of all delivered products. Now, I want this sum to be saved and shown as a variable (total_sum) in the delivery order itself, to see the total price of the delivery order.

First, I tried using a related field, but since there is only a reference from the stock picking model to the stock moves model (and not the other way around), this was no option.

Next, I tried using a compute field:

​total_sum = 0
​for rec in self.stock_move:
	​total_sum += rec.x_studio_total_price
self.x_studio_total_sum = total_sum

But keep having this value error:

ValueError: forbidden opcode(s) in 'total_sum = 0\nfor rec in self.stock_move:\n  total_sum += rec.x_studio_total_price\nself.x_studio_total_sum = total_sum': STORE_ATTR

What am I doing wrong? Is there another way to easily save an aggregated sum in a variable?