Unhashable type : 'list' error in Python

Question

I have already checked some question-answers related to Unhashable type : 'list' in stackoverflow, but none of them helped me. Here is my partial code:

keyvalue = {};
input_list_new = input_list;

for file in os.listdir('Directory/'):
    pathname = os.path.join('Directory/', file)
    dict_table = []; # creates blank 2d array
    with open(pathname) as dict_file:
        for line in dict_file:
            dict_table.append(line.strip().split("\t"))
    dict_list = [];
    for i in list(range(0, len(dict_table))):
        dict_list.append(dict_table[i][0])
    matched = list(set(dict_list) & set(input_list)) 
    for i in list(range(0, len(matched))):
        temp = [dict_table[0][0]] + dict_table[(dict_list.index(matched[i]))]

        input_list_new.insert((input_list_new.index(matched[i])), temp)

        dict = {matched[i] : temp}
        keyvalue.update(dict)

where dict_table is a list of lists, dict_list is just a list & keyvalue is a python dictionary. The entire code runs well when ever I comment the line input_list_new.insert((input_list_new.index(matched[i])), temp) , but without that line being commented, it shows Unhashable type : 'list' error.

Answer 1

The error message does not correspond to the line

input_list_new.insert((input_list_new.index(matched[i])), temp)

being commented out. If anything, the culprit is the line

dict = {matched[i] : temp}

The problem should be that you are trying to use a list as your dictionary key. Here is the problem in a simple reproducible way:

{[]: 5}  # throws TypeError: unhashable type: 'list'

The reason it fails, is because a dictionary is also be called a hashmap (in other languages). The key must be hashable, and in Python trying to use a list as the key throws your error becauses lists are not hashable (see "hashable" entry here ).

Avoid using a list as your dictionary key will fix the problem.

Answer 2

这是我的猜测...。您提到错误与matched = list(set(dict_list) & set(input_list))的行matched = list(set(dict_list) & set(input_list)) ..可能是因为在input_list或dict_list ，列表中都有一个列表。 ...集合中的项目需要可哈希化，因此是不可变的。例如，您不能执行set([1,5,6,[1,3]]) ...这会导致无法哈希的类型列表错误。 ..但您可以执行set([1,5,6,(1,3)])因为元组是不可变且可哈希的