Typeerror: unhashable type: list

This error occurs when you try to use a list as key in the dictionary or set. As you know 'list' is an unhashable object that can not be used as a key for any dictionary or set. In simple terms, this error occurs when you try to hash a 'list'typeerror: unhashable type: list is an unhashable object.

The TypeError: unhashable type: 'list' usually occurs when you try to use a list object as a set element or dictionary key and Python internally passes the unhashable list into the hash function. But as lists are mutable objects, they do not have a fixed hash value. The easiest way to fix this error is to use a hashable tuple instead of a non-hashable list as a dictionary key or set element. This is not a trivial problem because Python lists are mutable and, therefore, not hashable. In fact, the error can be reproduced most easily when calling hash lst on a list object lst. Because you cannot successfully pass a list into the hash function, you cannot directly use lists as set elements or dictionary keys.

Typeerror: unhashable type: list

The error message "TypeError: unhashable type: 'list' " typically indicates an attempt to employ a list as a hashable argument. Hashing an unhashable object leads to an error. For example, using a list as a dictionary key is infeasible since lists aren't hashable. The conventional resolution involves converting the list to a tuple. Dictionary keys must be immutable types and list is a mutable type. You'll have to change your list into tuples if you want to put them as keys in your dictionary. The hash function is a built-in Python method utilized to generate a distinct numerical value. It can be employed with user-defined objects that remain unaltered after initialization. This characteristic finds significance primarily in the context of dictionary keys. While tuples might appear similar to lists, they frequently serve distinct roles and have different applications. Tuples are immutable and typically comprise a heterogeneous sequence of elements accessible through unpacking or indexing. In contrast, lists are mutable and generally consist of homogeneous elements accessed by iteration. Hashing is a fundamental concept in computer science that facilitates the creation of efficient, pseudo-random access data structures for rapid storage and retrieval of substantial data.

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It will allow Python to create unique hash values for the keys. This error shows that the fruits key [2,4,6 ] is a list and not a hashable type in Python. Dictionary keys must be immutable types, and the list is a mutable type. The easiest way to resolve this error is to convert the list into a tuple. Though tuples may seem similar to lists, they are often used for different purposes. Tuples are immutable and contain a heterogeneous sequence of elements that are accessed via unpacking or indexing. On the other hand, lists are mutable, and the elements are homogeneous, and the elements are accessed by iterating over the list.

For example, using a list as a key in a Python dictionary will throw the TypeError because you can only use hashable data types as a key. This tutorial will go through the error in detail and how to solve it with the help of code examples. TypeError occurs whenever you try to perform an illegal operation for a specific data type object. In the example, the illegal operation is hashing, and the data type is List. By definition, a dictionary key needs to be hashable. An object is hashable if it has a hash value that remains the same during its lifetime. A hash value is an integer Python uses to compare dictionary keys while looking at a dictionary.

Typeerror: unhashable type: list

In Python, a TypeError is raised when an operation or function is applied to an object of an inappropriate type. This error occurs when we try to use a list which is an unhashable type object in a place that requires a hashable type. In this tutorial, we will discuss the reasons behind this error and how to fix it. In Python, hashable types are those which have a hash value that remains constant throughout its lifetime.

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Python Not Equal Operator! To resolve this, consider using tuples, which are immutable and can serve as hashable alternatives in such contexts. It will become hidden in your post, but will still be visible via the comment's permalink. Blog Code Tutorials Python. What's Next? We do this by dividing the total of all grades by how many grades have been recorded. James Gallagher is a self-taught programmer and the technical content manager at Career Karma. While values can be of any data type, from lists to strings , only hashable objects are acceptable as keys. The hash function is a built-in Python method utilized to generate a distinct numerical value. Your experience Beginner Intermediate Advanced. In fact, the error can be reproduced most easily when calling hash lst on a list object lst. What are literals in python? Hashable objects in Python int, float, decimal, complex, bool, string, tuple, range, frozenset, bytes Unhashable objects in Python list, dict, set, bytearray, user-defined classes.

This article will discuss the TypeError: unhashable type: 'list' and how to fix it in Python. Dictionaries is a data structure in Python that works in key-value pairs, every key has a value against it, and to access the values of values, you will need the keys like array indices. We have used a list ["a","b"] as the key , but the compiler has thrown a TypeError: unhashable type: 'list'.

Keys are the labels associated with a particular value. While tuples might appear similar to lists, they frequently serve distinct roles and have different applications. This error occurs when trying to hash a list, which is an unhashable object. Hashable objects are objects with a hash value that does not change over time. Are you sure you want to hide this comment? It will allow Python to create unique hash values for the keys. Net VB. Self-Learning Bootcamps vs. This error occurs when you try to use a list as key in the dictionary or set. We believe in transparency and want to ensure that our users are aware of how we generate revenue to support our platform. Submit Preview Dismiss.