Python) Create a new list with a list

names = [
  ["Joe", "Smith"], ["Mary", "Smith"], 
  ["Pete", "Smith"], ["Lily", "Smith"], 
  ["Heinz", "Maus"], ["Brigita", "Maus"], 
  ["Juergen", "Maus"], ["Jean", "St. Croix"], 
  ["sophie", "St. Croix"]
]

last_name_dict = {} #A dictionary for gathering people with the same last name
For first_name, last_name in names: # Touring the name,
  If last_name not in last_name_dict: # If the dictionary does not have a corresponding sex,
    last_name_dict[last_name] = [] # Put an empty list with the last name as the key in the dictionary.

  last_name_dict[last_name].append(first_name)# Put the same name in the list of last names.

last_name_list = [] #List for output
For last_name, first_names in last_name_dict.items(): # While touring the dictionary collected above,
  item = [last_name, len(first_names), first_names] # Create a list of last names, people, and names.
  last_name_list.append(item) #Add to list.

print(last_name_list) 

# # [['St. Croix', 2, ['Jean', 'sophie']], ['Maus', 3, ['Heinz', 'Brigita', 'Juergen']], ['Smith', 4, ['Joe', 'Mary', 'Pete', 'Lily']]]