Django template can't loop defaultdict

Question

import collections

data = [
  {\'firstname\': \'John\', \'lastname\': \'Smith\'}, 
  {\'firstname\': \'Samantha\', \'lastname\': \'Smith\'}, 
  {\'firstname\': \'sh         


        

Answer 1

You can avoid the copy to a new dict by disabling the defaulting feature of defaultdict once you are done inserting new values:

new_data.default_factory = None

Explanation

The template variable resolution algorithm in Django will attempt to resolve new_data.items as new_data['items'] first, which resolves to an empty list when using defaultdict(list).

To disable the defaulting to an empty list and have Django fail on new_data['items'] then continue the resolution attempts until calling new_data.items(), the default_factory attribute of defaultdict can be set to None.