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.

Explore your training options in 10 minutes Get Started. Python dictionaries only accept hashable data types as a key in a dictionary. A list is not a hashable data type. In this guide, we talk about what this error means and why you see it in your code. Dictionaries have two parts: keys and values. Keys are the labels associated with a particular value.

Typeerror: unhashable type: list

The Python TypeError: unhashable type: 'list' usually means that a list is being used as a hash argument. This error occurs when trying to hash a list, which is an unhashable object. For example, using a list as a key in a Python dictionary will cause this error since dictionaries only accept hashable data types as a key. The standard way to solve this issue is to cast a list to a tuple, which is a hashable data type. Install the Python SDK to identify and fix these undefined errors. Tuples are similar to lists but are immutable. They usually contain a heterogeneous sequence of elements that are accessed via unpacking or indexing. On the other hand, lists are mutable and contain a homogeneous sequence of elements that are accessed by iterating over the list. Immutable objects such as tuples are hashable since they have a single unique value that never changes. Hashing such objects always produces the same result, so they can be used as the keys for dictionaries. The Python TypeError: Unhashable Type: 'List' can be fixed by casting a list to a tuple before using it as a key in a dictionary:. In the example above, the tuple function is used to convert the list to a tuple. The above code runs successfully, produces the following output:. Unhashable type errors appear in a Python program when a data type that is not hashable is used in code that requires hashable data. An example of this is using an element in a set or a list as the key of a dictionary.

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 typeerror: unhashable type: list. Being able to track, analyze, and manage errors in real-time can help you to proceed with more confidence. It can be employed with user-defined objects that remain unaltered after initialization.

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.

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'. The hash function is used to find the hash value of a given object, but the object must be immutable like string , tuple , etc. To fix the TypeError in Python, you have to use immutable objects as the keys of dictionaries and as arguments to the hash function. Notice in the above code the hash function works perfectly with mutable objects like tuple and string. This time we provide a string "a" as the key, which is fine to work with because strings are mutable. Zeeshan is a detail oriented software engineer that helps companies and individuals make their lives and easier with software solutions. TypeError: unhashable type: 'list'. Hash of a string object Hash of a tuple object Hash of a string message

Typeerror: unhashable type: list

Do you know what to do to fix it? For example, as an item of a set or as a key of a dictionary. This error can occur in multiple scenarios and in this tutorial we will analyse few of them to make sure you know what to do when you see this error. By definition a dictionary key needs to be hashable. The error is exactly the same, but why are we seeing this error when converting the array into a set?

Hannah waddingham height

Aug 31, But what if you really need a mutable set or dictionary key? To help students reach higher levels of Python success, he founded the programming education website Finxter. This commission is reinvested into growing the community to provide coaching at zero cost to their members. Feel free to check out more free tutorials and cheat sheets for learning and improving your Python skills in our free email academy:. Hashable is a feature of Python objects that determines whether the object has a hash value or not. Christian Mayer found his love for teaching computer science students. In python, hashing is the method of encoding the data into a fixed-size integer which represent the original value. While working as a researcher in distributed systems, Dr. 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. Submit Preview Dismiss. Their hash values can change over time. Your experience Beginner Intermediate Advanced. Traceback most recent call last : File "main.

The Python TypeError: unhashable type: 'list' usually means that a list is being used as a hash argument.

Hashable is a feature of Python objects that determines whether the object has a hash value or not. The easiest way to resolve this error is to convert the list into a tuple. Without it we would be flying blind. The above code runs successfully, produces the following output:. Christian Mayer found his love for teaching computer science students. Hide child comments as well Confirm. Sign Up Today! Install the Python SDK to identify and fix these undefined errors. Is Python call-by-value or call-by-reference? Leave a Reply Cancel reply Your email address will not be published. Hashable objects are objects with a hash value that does not change over time. But what if you really need a mutable set or dictionary key? What's Next? In each iteration of the for loop, we calculate the average of all the grades a student has earned. What is the use of lambda in Python?