Fix TypeError: unhashable type: 'dict' in Python

A TypeError occurs in Python when an operation or function is applied to an object of inappropriate type. One such type error is "TypeError: unhashable type: dict," which is raised when we try to use a dictionary as a key in a set or use it as a key in another dictionary.

In Python, hashable objects are used as keys in dictionaries and elements in sets. A hashable object has a hash value that never changes during its lifetime (it needs a hash() method), and it can be compared to other objects for equality (it needs an eq() method). To reproduce this error, you can use the following examples:

Example 1: Using a dictionary as a key in a set

dict1 = {'Name': 'John Doe', 'Age': 30}
set1 = {dict1}

Output:

TypeError: unhashable type: 'dict'

In the above example, we are trying to add the dictionary dict1 to a set set1. Since dictionaries are mutable, their hash value can change, and thus they cannot be used as keys in sets.

Example 2: Using a dictionary as a key in another dictionary

dict1 = {'Name': 'John Doe', 'Age': 30}
dict2 = {dict1: 'Details'}

Output:

TypeError: unhashable type: 'dict'

In the above example, we are trying to use dict1 as a key in another dictionary dict2. Since dictionaries are mutable, their hash value can change, and thus they cannot be used as keys in another dictionary.

Solution for TypeError: unhashable type: 'dict'

One solution to the "TypeError: unhashable type: dict" is to convert the dictionary to a tuple or a frozenset. Tuples and frozensets are hashable and can be used as keys in sets and dictionaries.

Example:

dict1 = {'Name': 'John Doe', 'Age': 30}
tuple1 = tuple(dict1.items())
set1 = {tuple1}
print(set1)

Output:

{(('Name', 'John Doe'), ('Age', 30))}

In the above example, we have converted the dictionary dict1 to a tuple tuple1 using the tuple() method and the .items() method of the dictionary. Now, we can use tuple1 as a key in the set set1.

Conclusion

In conclusion, the "TypeError: unhashable type: dict" error occurs when we try to use a dictionary as a key in a set or another dictionary. To resolve this error, we need to convert the dictionary to a tuple or frozenset, which are hashable and can be used as keys.

See also: TypeError: 'module' object is not callable in Python

TypeError: unhashable type: 'dict' - FAQs