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Python - TypeError – NoneType Object not Subscriptable

July 06, 2023
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TypeError: 'NoneType' object is not subscriptable

The mistake is self-evident. You are attempting to subscript an object that is actually a None.

Example 1

list1=[5,1,2,6] # Create a simple list
order=list1.sort() # sort the elements in created list and store into another variable.
order[0] # Trying to access the first element after sorting

TypeError Traceback (most recent call last)

in ()
list1=[5,1,2,6]
order=list1.sort()
----> order[0]

TypeError: 'NoneType' object is not subscriptable

Sort () function returns None due to TypeError: 'NoneType' object is not subscriptable. It affects the source item directly. So you're attempting to slice or subscript the empty None object.

print(order) # Let’s see the data present in the order variable.
None # It’s None

REMEDY

Sort () function returns None due to TypeError: 'NoneType' object is not subscriptable. It affects the source item directly. So you're attempting to slice or subscript the empty None object.Verify whether the returned value is None by looking at it. If it's None, then make appropriate plans for the alternatives.

We are attempting to sort the values in a list in the example above. When sort() is called, the source object is changed without any output being produced. To fix the problem, we might attempt other approaches.

either operate on the source directly.

list1=[5,1,2,6] #A simple List
list1.sort() # Sort the elements of source object directly.
list1[0] # Access the first element of the sorted list.
Output: 1
or use another method that returns the object with sorted values of the list.

list1=[5,1,2,6]              # A simple list created
order=sorted(list1) # Sorting the elements of the above list and store them into another list.
order[0]                  # Access first element of a new list created.

Output: 1

Example 2

list1=[1,2,4,6]                           # Create a list with a few elements
reverse_order=list1.reverse() # Reverse the order of elements and store into other variable.
reverse_order[0:2]    # Access the first two elements after reversing the order.

TypeError Traceback (most recent call last)

in ()
     list1=[1,2,4,6]
     reverse_order=list1.reverse()
----> reverse_order[0:2]

TypeError: 'NoneType' object is not subscriptable

the reverse() method also won't return anything but None, it directly acts upon the source object. So you are trying to slice/subscript the None object which holds no data at all.

print(reverse_order) # Prints the data inside reverse_order

None #It’s None
REMEDY

Always verify whether None is present in the returned values. If it's None, then consider your options carefully.

The items of a list are being attempted to be reversed in the example above. Reverse() does not return anything; instead, it changes the source object. To fix the problem, we might attempt other approaches.
- Either operate on the source directly.
  
  list1=[1,2,4,6] #A simple list
  list1.reverse() # Reverse the order of elements in the above list
  list1[0:2] # Accessing the first two elements in a reversed list.
  
  Output: [6, 4]
- Use another method that returns the object with reversed values of the list.
  
  list1=[1,2,4,6] # A list
  reverse_order=list(reversed(list1)) # Reversing the order and store into another list.
  reverse_order[0:2] # Accessing the first 2 elements of reversed list.
  
  Output: [6, 4]
Example 3

Import numpy as np # Import numpy package

def addition(arrays):    # A function which performs addition operation
total=arrays.sum(axis=1) # Performing row wise addition in numpy array

a=np.arange(12).reshape(6,2) #Creating a 2D array
total=addition(a)                        #Calling the function
total[0:4]                                    #Accessing first 4 elements on total

TypeError Traceback (most recent call last)

in ()

    a=np.arange(12).reshape(6,2)
    total=addition(a)
----> total[0:4]

TypeError: 'NoneType' object is not subscriptable

As we can see, the addition function in this case is not returning anything. The resulting object will yield the aforementioned error when we attempt to subscript it because it contains nothing.

print(total) #print total
None

REMEDY

Always verify whether None is present in the returned values. If it's None, then consider your options carefully.

In the example above, we're attempting to display the total of a 2D array's row-wise items. To fix the problem, we might attempt other approaches.
- Either print the sum inside the function directly.
  
  import numpy as np # Import numpy package for mathematical operations
  
  defaddition1(arrays):                  # Function to perform addition
  total1=arrays.sum(axis=1)    # Row-wise sum in 2D numpy array
  print('row wise sum',total1[0:4]) # Printing first 4 elements of total
  
  a=np.arange(12).reshape(6,2) # Creating a 2D array
  print('input array \n',a)              # Printing a comment
  print('*********')
  addition1(a)    # Calling the function
  
  input array
  [[ 0 1]
  [ 2 3]
  [ 4 5]
  [ 6 7]
  [ 8 9]
  [10 11]]
  *********
  
  row wise sum [ 1 5 9 13]
- import numpy as np # Import numpy package
  
  defaddition2(arrays): # Defining a function which performs addition
  return total # Returning the sum
  
  a=np.arange(12).reshape(6,2) # Creating a 2D array
  print('input array \n',a)
  print('*********')
  total2= addition2(a) # Calling the function
  print('row wise sum',total2[0:4]) # Printing first 4 elements of total
  
  input array
  [[ 0 1]
  [ 2 3]
  [ 4 5]
  [ 6 7]
  [ 8 9]
  [10 11]]
  *********
  row wise sum [ 1 5 9 13]
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Example4

import cv2             # Importing opencv package to read the image
import numpy as np                  # Importing numpy package
import matplotlib.pyplot as plt           # Package for visualization
image=cv2.imread('download.jpeg')    # Reading the image
plt.imshow(image[65:120])              # Show the part of image

TypeError Traceback (most recent call last)

in ()
importmatplotlib.pyplotasplt
image=cv2.imread('download.jpeg')
----> plt.imshow(image[65:120])

TypeError: 'NoneType' object is not subscriptable

Here we are trying to print a cut short of the image. Above error which is coming as OpenCV is unable to read the image

print(image)
None

REMEDY

Look for the proper path, then fix the image's format. OpenCV won't be able to load the image if the path or image type are incorrect. The picture type is 'jpg' here rather than 'jpeg.'

import cv2 # Import opencv package to read the image
import numpy as np # Numpy package
import matplotlib.pyplot as plt         # For visualization
image=cv2.imread('download.jpg') # Reading the image
plt.imshow(image[65:120])             # Showing the part of image

Output:

Conclusion: We frequently encounter the TypeError issue while attempting to compute across incompatible data types. Anytime we attempt to subscript or slice an empty data object or data of no type, we encounter the TypeError: None-type not subscriptable error.