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Python Django Forms More on Models Quiz Model

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10,440 Points

Where does step.order come from?

Kenneth Love I do not understand, how do we access step.order in lambda function?

 def course_detail(request, pk):
    course = get_object_or_404(models.Course, pk=pk)
    steps = sorted(chain(course.text_set.all(), course.quiz_set.all()),
                   key=lambda step: step.order)
    return render(request, 'courses/course_detail.html', {
        'course': course,
        'steps': steps

1 Answer

Kenneth Love
Kenneth Love
Treehouse Guest Teacher

sorted()'s key argument can be a callable (function, effectively). We're using a lambda so we don't have to write out a whole new function or, in this case, use getattr. We're giving the lambda an argument named step and this argument will be filled in with whatever item sorted is currently looking at in the iterable (it reads through each element in the iterable and compares them to each other). We're making the lambda return the order attribute from each step.

In plainer English, what sorted is doing here is taking a big pile of steps and ordering them based on their order attribute.