This piece of code is giving me an error unhashable type: dict can anyone explain to me what the solution is?
negids = movie_reviews.fileids('neg')
def word_feats(words):
return dict([(word, True) for word in words])
negfeats = [(word_feats(movie_reviews.words(fileids=[f])), 'neg') for f in negids]
stopset = set(stopwords.words('english'))
def stopword_filtered_word_feats(words):
return dict([(word, True) for word in words if word not in stopset])
result=stopword_filtered_word_feats(negfeats)
3 Answers
You're trying to use a dict as a key to another dict or in a set. That does not work because the keys have to be hashable. As a general rule, only immutable objects (strings, integers, floats, frozensets, tuples of immutables) are hashable (though exceptions are possible). So this does not work:
>>> dict_key = {"a": "b"}
>>> some_dict[dict_key] = True
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'dict'
To use a dict as a key you need to turn it into something that may be hashed first. If the dict you wish to use as key consists of only immutable values, you can create a hashable representation of it like this:
>>> key = frozenset(dict_key.items())
Now you may use key as a key in a dict or set:
>>> some_dict[key] = True
>>> some_dict
{frozenset([('a', 'b')]): True}
Of course you need to repeat the exercise whenever you want to look up something using a dict:
>>> some_dict[dict_key] # Doesn't work
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'dict'
>>> some_dict[frozenset(dict_key.items())] # Works
True
If the dict you wish to use as key has values that are themselves dicts and/or lists, you need to recursively "freeze" the prospective key. Here's a starting point:
def freeze(d):
if isinstance(d, dict):
return frozenset((key, freeze(value)) for key, value in d.items())
elif isinstance(d, list):
return tuple(freeze(value) for value in d)
return d
A possible solution might be to use the JSON dumps() method, so you can convert the dictionary to a string ---
import json
a={"a":10, "b":20}
b={"b":20, "a":10}
c = [json.dumps(a), json.dumps(b)]
set(c)
json.dumps(a) in c
Output -
set(['{"a": 10, "b": 20}'])
True
def frozendict(d: dict):
return frozenset(d.keys()), frozenset(d.values())
