Count vs len on a Django QuerySet

Question

In Django, given that I have a QuerySet that I am going to iterate over and print the results of, what is the best option for counting the objects? len(qs

Answer 1

Summarizing what others have already answered:

• len() will fetch all the records and iterate over them.
• count() will perform an SQL COUNT operation (much faster when dealing with big queryset).

It is also true that if after this operation, the whole queryset will be iterated, then as as whole it could be slightly more efficient to use len().

However

In some cases, for instance when having memory limitations, it could be convenient (when posible) to split the operation performed over the records. That can be achieved using django pagination.

Then, using count() would be the choice and you could avoid to have to fetch the entire queryset at once.