python_syntax_defaultdict

gistfile1.txt

from collections import defaultdict

word_lists = defaultdict(list)

pairs = [('a', 1), ('b', 2), ('c', 3), ('a', 4), ('b', 5)]

for key, value in pairs:
  word_lists[key].append(value) # Append value to list

print(word_lists.get('d', []))
print(word_lists.get('a', []))