Pythonic custom sort for letter grades 'D', 'C-' ,…, 'A+'?

Question

Is there a more Pythonic, compact, intuitive way to sort letter-grades than this (without using a custom dict)?

grades = [\'B-\',\'C\',\'B\',\'C+\',\'A\',\'D+\',         


        

Answer 1

Yes-ish?

>>> sorted(grades, key=lambda g: g + ',')
['A+', 'A', 'A-', 'B+', 'B', 'B-', 'C+', 'C', 'C-', 'D+', 'D']

Clearly more compact, and I'd say also pythonic, just not very intuitive :-P

Works because '+' < ',' < '-'.

---

Another one:

>>> sorted(grades, key=lambda g: (g[0], ' -'.find(g[1:])))
['A+', 'A', 'A-', 'B+', 'B', 'B-', 'C+', 'C', 'C-', 'D+', 'D']

Suffix + won't be found in ' -', so find returns -1. Empty suffix results in 0, and suffix - results in 1.

Answer 2

No.

modmap = {
  '-': 0,
  '': 1,
  '+': 2
}

print(sorted(grades, key=lambda x: (-ord(x[0]), modmap[x[1:]])))