Function takes a dictionary called 'names' as a parameter; 'names' should be a dictionary where the key is a last name and the value is a list of first names. Returns a new dictionary where each key is the first letter of a last name, and the value is the number of people whose last name begins with that letter.

count_first_letter.py

def count_first_letter(names):
  letters = {}
  for key in names:
    first_letter = key[0]
    if first_letter not in letters:
      letters[first_letter] = 0
    letters[first_letter] += len(names[key])
  return letters

# Uncomment these function calls to test your  function:
print(count_first_letter({"Stark": ["Ned", "Robb", "Sansa"], "Snow" : ["Jon"], "Lannister": ["Jaime", "Cersei", "Tywin"]}))
# should print {"S": 4, "L": 3}
print(count_first_letter({"Stark": ["Ned", "Robb", "Sansa"], "Snow" : ["Jon"], "Sannister": ["Jaime", "Cersei", "Tywin"]}))
# should print {"S": 7}