Использование defaultdict
:
from collections import defaultdict
lst_1=['Apple', 'pie', 'is', 'the', 'most', 'delicious'] #list 1
lst_2=['It', 'is', 'Americas', 'best'] #list 2
d = defaultdict(list)
for i in lst_1:
d[i].append(1)
for i in lst_2:
d[i].append(2)
dict(d)
дает
{'Apple': [1], 'pie': [1], 'is': [1, 2], 'the': [1], 'most': [1], 'delicious': [1], 'It': [2], 'Americas': [2], 'best': [2]}