​1. sum() — Add Values in Recordsets

✅ What is sum()?

The sum() function returns the total of numeric values in an iterable.

📌 Realistic Odoo Example

Suppose you want to calculate the total amount from a list of sale orders.

total_amount = sum(self.mapped('amount_total'))

• self is a recordset of sale.order
  
  
• mapped('amount_total') gives a list of totals
  
  
• sum() adds all the totals together

➕ More Example:

total_qty = sum(self.order_line.mapped('product_uom_qty'))

This gives the total quantity of all products in the order lines.

 2. len() — Count Records or Items

✅ What is len()?

The len() function returns the number of items in a recordset or list.

📌 Realistic Odoo Example

Suppose you want to know how many order lines a sale order has:

line_count = len(self.order_line)

This returns the number of lines in the current order.

➕ More Example:

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✅ Summary Table

Function	Purpose	Example Use Case
sum()	Add numeric values	Total order amount, total quantity
len()	Count number of items in record/list	Count lines, records, filtered partners