return the two biggest numbers in a list of dictionaries

L = [{'a':3, 'b':5}, {'a': 2, 'b':6},{'a':1, 'b':8}]

def two_biggest(list):
  b_list = sorted(list, key=lambda x:x['b'])
  return b_list[-1], b_list[-2]

two_biggest(L)