Return key with highest value

Question

I have the following graph:

graph = {0 : {5:6, 4:8},
1 : {4:11},
2 : {3: 9, 0:12},
3 : {},
4 : {5:3},
5 : {2: 7, 3:4}}

I am trying to return the key that has the highest value in this graph. The expected output in this case would be 2 as key 2 has the highest value of 12.

Any help on how I can achieve this would be greatly appreciated.

Answer 1

Find the key whose maximum value is maximal:

max((k for k in graph), key=lambda k: max(graph[k].values(), default=float("-inf")))

The empty elements are disqualified by the ridiculous maximum. Alternately, you can just pre-filter such keys:

max((k for k in graph if graph[k]), key=lambda k: max(graph[k].values()))