Count number of Items in a Dictionary Value that is a List

Count number of all Items in a Dictionary Value that is a List.

DOL = {'Alex': ['subj1', 'subj2', 'subj3'],
       'David': ['subj1', 'subj2'],
      }
cnt_items = sum(map(len, DOL.values()))

print(cnt_items)     # 5

See also

https://www.w3resource.com/python-exercises/dictionary/python-data-type-dictionary-exercise-34.php