Write a function that inverts a dictionary with non-unique values. Keys that map to the same values should be appended to a list in the inverted dictionary

Solution

def invert_dict_non_unique(my_dict):
  my_inverted_dict = dict()
  for key, value in my_dict.items():
      my_inverted_dict.setdefault(value, list()).append(key)
  return my_inverted_dict