alphabets = {'it': {'a', 'b', 'c', 'd', 'e', 'à', 'ì'},
             'en': {'a', 'b', 'c', 'd', 'e'},
             'pl': {'a', 'b', 'c', 'd', 'e', 'ę', 'ś'}}
 
def delta(lang):
    d = set(alphabets[lang]) # make a copy
    for key, alphabet in alphabets.items():
        if key == lang:
            continue
        d -= alphabet
        if not d:
            break
    return d
 
unique = {lang: delta(lang) for lang in alphabets}
 
print(unique)

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