Python summing values in list if it exists in another list

Question

I have a list and a set:

a_list = [[\'1\', 2], [\'2\', 1], [\'1\', 1]]

b_list = {\'1\', \'2\'}

I\'m looking to correspond the items in b_list

Answer 1

Use a dict for grouping:

d = {}
for k, v in a_list:
    d[k] = d.get(k, 0) + v
print([[k, d[k]] for k in b_list])

prints:

[['2', 1], ['1', 3]]