Group all keys in dict that have identical values, when the values are lists

Question

I have a dict:

my_dict = {
  'train_1': ['a', 'b','c'],
  'train_2': ['a', 'b', 'c', 'd'],
  'train_3': ['a', 'b', 'c', 'd'],
  'train_4': ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'],
  'train_5': ['a', 'b', 'c', 'd', 'e', 'f'],
  'train_6': ['a', 'b', 'c', 'd']
}

I need to find all keys in the dict that have identical lists.

The output should be:

{
  'group_1': ['train1'],
  'group_2': ['train_2', 'train_3', 'train_6'],
  'group_3': ['train_4'],
  'group_4': ['train_5'],
}

I can use something like this for the task when the values in the dict are not lists:

flipped = {}

for key, value in my_dict.items():
    print(value)
    if value not in flipped:
        flipped[value] = [key]
    else:
        flipped[value].append(key)

But how can I achieve this when the values are lists ?

Answer 1

Continuing from the comments, you could change the lists to tuple and then use them as the keys:

my_dict = {
  'train_1': ['a', 'b','c'],
  'train_2': ['a', 'b', 'c', 'd'],
  'train_3': ['a', 'b', 'c', 'd'],
  'train_4': ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'],
  'train_5': ['a', 'b', 'c', 'd', 'e', 'f'],
  'train_6': ['a', 'b', 'c', 'd']
}

flipped = {}

for key, value in my_dict.items():
    if tuple(value) not in flipped:
        flipped[tuple(value)] = [key]
    else:
        flipped[tuple(value)].append(key)
print(flipped)

OUTPUT:

{('a', 'b', 'c'): ['train_1'], ('a', 'b', 'c', 'd'): ['train_3', 'train_6', 'train_2'], ('a', 'b', 'c', 'd', 'e', 'f'): ['train_5'], ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h')
: ['train_4']}     

EDIT :

once, filtered. you could iterate over the new dict and assign the desired keys:

grouped_dct = {}
i = 1
for k,v in flipped.items():
    grouped_dct['group_' + str(i)] = v
    i += 1

print(grouped_dct)

OUTPUT:

{'group_1': ['train_4'], 'group_2': ['train_5'], 'group_3': ['train_2', 'train_6', 'train_3'], 'group_4': ['train_1']}  

                                                                                                                                                          

Answer 2

if order of element in the list matters then below should work for you.

flipped = {}

for key, value in my_dict.items():
    print(value)
    newVal = ''.join(x for x in value)
    if newVal not in flipped:
        flipped[newVal] = [key]
    else:
        flipped[newVal].append(key)
print(flipped)