Question

I’m trying to compare two dictionaries. My approach is to turn them into two separate lists of tuples and to then use the set module. Here is an illustration:

dict = {'red':[1,2,3],'blue':[2,3,4],'green':[3,4,5]}

dict1 = {'green':[3,4,5],'yellow':[2,3,4],'red':[5,2,6]}

intersection = set(set(dict.items()) & set(dict1.items()))

apparently, this is comparing two lists of tuples and python doesn’t like that. I get a TypeError: ‘list’ is unhashable error (or similar wording).

I would like intersection to contain [('green',[3,4,5])]. Any ideas?

Answer 1

shared_keyvals = dict( (key, dict1[key])
                       for key in (set(dict1) & set(dict2))
                       if dict1[key] == dict2[key]
                     )

You can even make this into a function:

def shared_keyvals(dict1, dict2):
    return dict( (key, dict1[key])
                 for key in (set(dict1) & set(dict2))
                 if dict1[key] == dict2[key]
               )

Obviously, if you prefer to not have the output in dictionary form, you can just remove the dict() call and replace with with list comprehension brackets ([]) instead.