Sort by key

Python’s list.sort method takes a key keyword parameter. key defaults to None, in which case the sort uses the conventional order (i.e., <= or whatever). If key isn’t None, it should be a function that takes elements of the list, which are sorted by their result on key.

Copy and paste in mergesort, and make it take a key parameter. Here’s an example interaction:

>>> mergesort(l, key=get_id)
[{'id': 73, 'name': 'Wen-Ding'}, {'id': 100, 'name': 'Michael'}, {'id': 112, 'name':
'Anvay'}]
>>> mergesort(l, key=get_name)
[{'id': 112, 'name': 'Anvay'}, {'id': 100, 'name': 'Michael'}, {'id': 73, 'name': 'We
n-Ding'}]