Composite dictionary in Python with multiple values from other dictionaries by identical key

Let me clarify right away – I'm not a programmer, I'm learning Python for my own specific purposes (processing data obtained from the network), so if my question seems naive and simple – please don't judge.

So, there are three different dictionaries with identical keys. The values are different, but they can match both within the same dictionary and across different dictionaries. For example (I made the values as a list because I understand that there's no other way to add values to a single key):

dict_1={'a': [2],    'b': [8],    'c': [6],    'd': [2]}dict_2={'a