Typeerror: unhashable type: list

It will allow Python to create unique hash values for the keys. This error typeerror: unhashable type: list 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.

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.

Typeerror: unhashable type: list

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. The easiest way to fix the TypeError: unhashable type: 'list' is to use a hashable tuple instead of a non-hashable list as a dictionary key. The error may also occur when you try to use a list as a set element. To fix the TypeError: unhashable type: 'list' when trying to use a list as a set element is to use a hashable tuple instead of a non-hashable list. For example, whereas set. If you want to convert a list of lists to a set, you can check out my detailed tutorial on the Finxter blog:.

A list is not a hashable data type. The hash function is a built-in Python method utilized to generate a distinct numerical value.

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' , which is an unhashable object. To fix this error, you can convert the 'list' into a hashable object like 'tuple' and then use it as a key for a dictionary as shown below. To fix this error, you can convert the 'list' into a hashable object like tuple then use it as a key for 'set' as shown below:. In python, hashing is the method of encoding the data into a fixed-size integer which represent the original value. You can hash only those objects which are hashable or objects that can't be altered.

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.

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.

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Want to explore tech careers? Confirm Flag. Leave a Reply Cancel reply Your email address will not be published. To fix this error, you can convert the 'list' into a hashable object like 'tuple' and then use it as a key for a dictionary as shown below. To help students reach higher levels of Python success, he founded the programming education website Finxter. As you know 'list' is an unhashable object that can not be used as a key for any dictionary or set. Rollbar automates error monitoring and triaging, making fixing Java errors easier than ever. You'll have to change your list into tuples if you want to put them as keys in your dictionary. Is Python call-by-value or call-by-reference? You can hash only those objects which are hashable or objects that can't be altered. What is a Coding Bootcamp? But as lists are mutable objects, they do not have a fixed hash value.

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.

Register Login. To resolve this, consider using tuples, which are immutable and can serve as hashable alternatives in such contexts. Thanks for keeping DEV Community safe. The example below demonstrates how to add a list into a dictionary as a value. Managing errors and exceptions in your code is challenging. What is the purpose pass statement in python? A list is not a hashable data type. Apply to top tech training programs in one click. Keys are the labels associated with a particular value. Why isn't there a switch or case statement in Python? Hashing such objects always produces the same result, so they can be used as the keys for dictionaries.