Typeerror nonetype object is not subscriptable python ошибка

You might have worked with list, tuple, and dictionary data structures, the list and dictionary being mutable while the tuple is immutable. They all can store values. And additionally, values are retrieved by indexing. However, there will be times when you might index a type that doesn’t support it. Moreover, it might face an error similar to the error TypeError: ‘NoneType’ object is not subscriptable.

list_example = [1, 2, 3, "random", "text", 5.64]
tuple_example = (1, 2, 3, "random", "text", 5.64)

print(list_example[4])
print(list_example[5])
print(tuple_example[0])
print(tuple_example[3])

What is a TypeError?

The TypeError occurs when you try to operate on a value that does not support that operation. The most common reason for an error in a Python program is when a certain statement is not in accordance with the prescribed usage. The Python interpreter immediately raises a type error when it encounters an error, usually along with an explanation.

Let’s reproduce the type error we are getting:

On trying to index the var variable, which is of NoneType, we get an error. The ‘NoneType’ object is not subscriptable.

Let’s break down the error we are getting. Subscript is another term for indexing. Likewise, subscriptable means an indexable item. For instance, a list, string, or tuple is subscriptable. None in python represents a lack of value for instance, when a function doesn’t explicitly return anything, it returns None. Since the NoneType object is not subscriptable or, in other words, indexable. Hence, the error ‘NoneType’ object is not subscriptable.

An object can only be subscriptable if its class has __getitem__ method implemented.

By using the dir function on the list, we can see its method and attributes. One of which is the __getitem__ method. Similarly, if you will check for tuple, strings, and dictionary, __getitem__ will be present.

However, if you try the same for None, there won’t be a __getitem__ method. Which is the reason for the type error.

Resolving the ‘NoneType’ object is not subscriptable

The ‘NoneType’ object is not subscriptable and generally occurs when we assign the return of built-in methods like sort(), append(), and reverse(). What is the common thing among them? They all don’t return anything. They perform in-place operations on a list. However, if we try to assign the result of these functions to a variable, then None will get stored in it. For instance, let’s look at their examples.

Example 1: sort()

list_example = [1, 11, 14, 10, 5, 3, 2, 15, 77]
list_example_sorted = list_example.sort()
print(list_example_sorted[0])

The sort() method sorts the list in ascending order. In the above code, list_example is sorted using the sort method and assigned to a new variable named list_example_sorted. On printing the 0th element, the ‘NoneType’ object is not subscriptable type error gets raised.

Recommended Reading | [Solved] TypeError: method Object is not Subscriptable

Example 2: append()

list_example = [1, 11, 14, 10, 5, 3, 2, 15, 77]
list_example_updated = list_example.append(88)
print(list_example_updated[5])

The append() method accepts a value. The value is appended to t. In the above code, the return value of the append is stored in the list_example_updated variable. On printing the 5th element, the ‘NoneType’ object is not subscriptable type error gets raised.

Example 2: reverse()

Similar to the above examples, the reverse method doesn’t return anything. However, assigning the result to a variable will raise an error. Because the value stored is of NoneType.

list_example = [1, 11, 14, 10, 5, 3, 2, 15, 77]
list_example_reversed = list_example.reverse()
print(list_example_reversed[5])

Recommended Reading | How to Solve TypeError: ‘int’ object is not Subscriptable

The solution to the ‘NoneType’ object is not subscriptable

It is important to realize that all three methods don’t return anything to resolve this error. This is why trying to store their result ends up being a NoneType. Therefore, avoid storing their result in a variable. Let’s see how we can do this, for instance:

Solution for sort() method

list_example = [1, 11, 14, 10, 5, 3, 2, 15, 77]
list_example.sort()
print(list_example[0])

Solution for append() method

list_example = [1, 11, 14, 10, 5, 3, 2, 15, 77]
list_example.append(88)
print(list_example[-1])

Solution for the reverse() method

list_example = [1, 11, 14, 10, 5, 3, 2, 15, 77]
list_example_reversed = list_example.reverse()
print(list_example_reversed[5])

TypeError: ‘NoneType’ object is not subscriptable, JSON/Django/Flask/Pandas/CV2

The error, NoneType object is not subscriptable, means that you were trying to subscript a NoneType object. This resulted in a type error. ‘NoneType’ object is not subscriptable is the one thrown by python when you use the square bracket notation object[key] where an object doesn’t define the __getitem__ method. Check your code for something of this sort.

None[something]

FAQs

Conclusion

This article covered TypeError: ‘NoneType’ object is not subscriptable. We talked about what is a type error, why the ‘NoneType’ object is not subscriptable, and how to resolve it.

In Python, NoneType is the type for the None object, which is an object that indicates no value. Functions that do not return anything return None, for example, append() and sort(). You cannot retrieve items from a None value using the subscript operator [] like you can with a list or a tuple. If you try to use the subscript operator on a None value, you will raise the TypeError: NoneType object is not subscriptable.

To solve this error, ensure that when using a function that returns None, you do not assign its return value to a variable with the same name as a subscriptable object that you will use in the program.

This tutorial will go through the error in detail and how to solve it with code examples.

TypeError: ‘NoneType’ object is not subscriptable

Let’s break up the error message to understand what the error means. TypeError occurs whenever you attempt to use an illegal operation for a specific data type.

The subscript operator retrieves items from subscriptable objects. The operator in fact calls the __getitem__ method, for example a[i] is equivalent to a.__getitem__(i).

All subscriptable objects have a __getitem__ method. NoneType objects do not contain items and do not have a __getitem__ method. We can verify that None objects do not have the __getitem__ method by passing None to the dir() function:

print(dir(None))

['__bool__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__']

If we try to subscript a None value, we will raise the TypeError: ‘NoneType’ object is not subscriptable.

Example #1: Appending to a List

Let’s look at an example where we want to append an integer to a list of integers.

lst = [1, 2, 3, 4, 5, 6, 7]

lst = lst.append(8)

print(f'First element in list: {lst[0]}')

In the above code, we assign the result of the append call to the variable name lst. Let’s run the code to see what happens:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [1], in <cell line: 5>()
      1 lst = [1, 2, 3, 4, 5, 6, 7]
      3 lst = lst.append(8)
----> 5 print(f'First element in list: {lst[0]}')

TypeError: 'NoneType' object is not subscriptable

We throw the TypeError because we replaced the list with a None value. We can verify this by using the type() method.

lst = [1, 2, 3, 4, 5, 6, 7]

lst = lst.append(8)

print(type(lst))

<class 'NoneType'>

When we tried to get the first element in the list, we are trying to get the first element in the None object, which is not subscriptable.

Solution

Because append() is an in-place operation, we do not need to assign the result to a variable. Let’s look at the revised code:

lst = [1, 2, 3, 4, 5, 6, 7]

lst.append(8)

print(f'First element in list: {lst[0]}')

Let’s run the code to get the result:

First element in list: 1

We successfully retrieved the first item in the list after appending a value to it.

Example #2: Sorting a List

Let’s look at an example where we want to sort a list of integers.

numbers = [10, 1, 8, 3, 5, 4, 20, 0]

numbers = numbers.sort()

print(f'Largest number in list is {numbers[-1]}')

In the above code, we assign the result of the sort() call to the variable name numbers. Let’s run the code to see what happens:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [8], in <cell line: 3>()
      1 numbers = [10, 1, 8, 3, 5, 4, 20, 0]
      2 numbers = numbers.sort()
----> 3 print(f'Largest number in list is {numbers[-1]}')

TypeError: 'NoneType' object is not subscriptable

We throw the TypeError because we replaced the list numbers with a None value. We can verify this by using the type() method.

numbers = [10, 1, 8, 3, 5, 4, 20, 0]

numbers = numbers.sort()

print(type(numbers))

<class 'NoneType'>

When we tried to get the last element of the sorted list, we are trying to get the last element in the None object, which is not subscriptable.

Solution

Because sort() is an in-place operation, we do not need to assign the result to a variable. Let’s look at the revised code:

numbers = [10, 1, 8, 3, 5, 4, 20, 0]

numbers.sort()

print(f'Largest number in list is {numbers[-1]}')

Let’s run the code to get the result:

Largest number in list is 20

We successfully sorted the list and retrieved the last value of the list.

Summary

Congratulations on reading to the end of this tutorial! The TypeError: ‘NoneType’ object is not subscriptable occurs when you try to retrieve items from a None value using indexing. If you are using in-place operations like append, insert, and sort, you do not need to assign the result to a variable.

For further reading on TypeErrors, go to the articles:

• How to Solve Python TypeError: ‘function’ object is not subscriptable
• How to Solve Python TypeError: ‘bool’ object is not subscriptable

Go to the online courses page on Python to learn more about Python for data science and machine learning.

Have fun and happy researching!

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