Sort Django objects by method with arguments

Question

I have a model called Task that returns a date depending on the user. It defines a method:

def date_for_display(self, user):
  # return some date for the task

I want to create a list of tasks sorted by the date returned by this method. I tried something like:

user = User.objects.get(username="jamie")
sorted(Task.objects.all(), key = lambda task: task.date_for_display(user))

But to no avail. I get NameError: global name 'user' is not defined. Do I need to use a closure of some sort to accomplish this? Not sure how to go about doing it.

Marcin · Accepted Answer · 2012-10-03 16:00:22Z

1

The easiest way to solve this is to use a keyword parameter in your lambda:

user = User.objects.get(username="jamie")
sorted(Task.objects.all(), key = lambda task, user=user: task.date_for_display(user))

This copies the user from the outer scope into the local scope of your lambda.

answered Oct 3, 2012 at 16:00

Marcin

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