Question

Is there a better way to sort a list by a nested tuple values than writing an itemgetter alternative that extracts the nested tuple value:

def deep_get(*idx):
  def g(t):
      for i in idx: t = t[i]
      return t
  return g

>>> l = [((2,1), 1),((1,3), 1),((3,6), 1),((4,5), 2)]
>>> sorted(l, key=deep_get(0,0))
[((1, 3), 1), ((2, 1), 1), ((3, 6), 1), ((4, 5), 2)]
>>> sorted(l, key=deep_get(0,1))
[((2, 1), 1), ((1, 3), 1), ((4, 5), 2), ((3, 6), 1)]

I thought about using compose, but that’s not in the standard library:

sorted(l, key=compose(itemgetter(1), itemgetter(0))

Is there something I missed in the libs that would make this code nicer?

The implementation should work reasonably with 100k items.

Context: I would like to sort a dictionary of items that are a histogram. The keys are a tuples (a,b) and the value is the count. In the end the items should be sorted by count descending, a and b. An alternative is to flatten the tuple and use the itemgetter directly but this way a lot of tuples will be generated.

Answer 1

Yes, you could just use a key=lambda x: x[0][1]