How to Solve this problem

Question

Hi all

i need to know what is the error in this code

%for product, lines in groupby(trip.order_lines, lambda l : l.product_id.name) :
<% qt = int(sum([l.qty for l in lines])) %>

i try to get the sm of all product quantity , but i didn't get it i get product and thier quantity not gruoped
what can i do

Jos De Graeve · Accepted Answer

Hi,

Have you checked that your list trip.order_lines is sorted by product ?

The operation of  groupby() [1]  is similar to the uniq filter in Unix. It generates a break or new group every time the value of the key function changes (which is why it is usually necessary to have sorted the data using the same key function). That behavior differs from SQL’s GROUP BY which aggregates common elements regardless of their input order.

Regards,

Jos

[1] https://docs.python.org/2/library/itertools.h

mostafa · Answer

@Jos De Graeve , tanks alot it worked fine with me

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