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.

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.

Typeerror: unhashable type: list

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. While values can be of any data type, from lists to strings , only hashable objects are acceptable as keys. Hashable objects are objects with a hash value that does not change over time. Examples of hashable objects are tuples and strings. Lists do not have an unchanging hash value. Their hash values can change over time. This means you cannot specify a list as a dictionary key. This list will contain dictionary records of each student and their grades. Each dictionary contains two keys: name and grades.

Hashable is a feature of Python objects that determines whether the object has a hash value or not.

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 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.

Typeerror: unhashable type: list

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.

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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. What is the use of lambda in Python? Once unpublished, all posts by itsmycode will become hidden and only accessible to themselves. Immutable objects such as tuples are hashable since they have a single unique value that never changes. Want to explore tech careers? We believe in transparency and want to ensure that our users are aware of how we generate revenue to support our platform. We believe that user-generated reviews offer valuable insights and diverse perspectives, helping our users make informed decisions about their educational and career journeys. In fact, the error can be reproduced most easily when calling hash lst on a list object lst. Python dictionaries only accept hashable data types as a key in a dictionary. How do you protect Python source code? What is the difference between runtime and compile time?

Explore your training options in 10 minutes Get Started. Python dictionaries only accept hashable data types as a key in a dictionary.

Your phone number. Here is what you can do to flag itsmycode: Make all posts by itsmycode less visible itsmycode consistently posts content that violates DEV Community's code of conduct because it is harassing, offensive or spammy. Dictionary keys must be immutable types and list is a mutable type. Find your bootcamp match. When our code parses this line on the first iteration of our loop, our code tries to create a dictionary with the following key and value:. Christian Mayer found his love for teaching computer science students. Confirm Flag. Dictionary keys must be immutable types, and the list is a mutable type. What are literals in python? Hashable is a feature of Python objects that determines whether the object has a hash value or not. Once unpublished, all posts by itsmycode will become hidden and only accessible to themselves. 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.