Python Hashable Dict

In Python, dictionaries are not hashable by default because they are mutable. However, you can create a hashable dictionary by using an immutable data structure to represent the dictionary.

One way to create a hashable dictionary is by converting it into a frozenset of its items. Here’s an example:

my_dict = {'a': 1, 'b': 2, 'c': 3}
hashable_dict = frozenset(my_dict.items())

Python hashable dict example

Another approach to creating a hashable dictionary is by using a custom class that encapsulates a dictionary and provides a hash function.

class HashableDict:
    def __init__(self, dictionary):
        self.dictionary = dictionary

    def __hash__(self):
        return hash(frozenset(self.dictionary.items()))

my_dict = {'a': 1, 'b': 2, 'c': 3}
hashable_dict = HashableDict(my_dict)

print(hashable_dict)

Output:

In this example, we define the HashableDict class that takes a dictionary as input and stores it as an attribute. The __hash__() method is implemented to compute the hash value based on the frozenset of the dictionary’s items. By creating an instance of HashableDict, you have a hashable dictionary that can be used in hash-based data structures.

Remember that when using a custom hashable dictionary, you need to ensure that the keys and values of the dictionary are themselves hashable for accurate hash computation.

Here’s an example of using the hashabledict class:

class hashabledict(dict):
    def __hash__(self):
        return hash(tuple(sorted(self.items())))

# Create hashable dictionaries
dict1 = hashabledict({'a': 1, 'b': 2, 'c': 3})
dict2 = hashabledict({'x': 10, 'y': 20})

# Use hashable dictionaries as keys in another dictionary
data = {
    dict1: 'Data 1',
    dict2: 'Data 2'
}

# Access data using hashable dictionaries as keys
print(data[dict1])  # Output: Data 1
print(data[dict2])  # Output: Data 2

Do comment if you have any doubts or suggestions on this Python dictionary topic.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.