dict1 = {1: "aaa", 2: "bbb"}
dict2 = {3: "ccc", 2: "XYZ", 4: "ddd"} # Note: key 2 overlaps
combined = dict1.copy()
for key, value in dict2.items():
if key in combined:
combined[key] += ", " + value
else:
combined[key] = value
print(combined)
'''
run:
{1: 'aaa', 2: 'bbb, XYZ', 3: 'ccc', 4: 'ddd'}
'''