In python, we can have many types of errors in our code. One of the most common errors is TypeError: list indices must be integers or slices, not str. In this article, we are going to see what causes this error and how can we fix this error.
This error mostly comes when we are working with lists in python. Whether we are printing the contents of a list or modifying any value at a particular position in the list. In this article, we will discuss some points to remember when working with lists so that the probability of occurring these types of errors will be much less.
Case 1:
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# Declare a List l1 = [10, 20, 30, 40, 50] # Get Index input from User index = input("Enter the Index at which you want to change value: ") # Get the number from user number = int(input("Enter the final value you want in list : ")) # Update the value in list l1[index] = number # Print the list after updation print(f"Updated list is : {l1}") |
Output:
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PS C : \ Users \ ASUS \ Desktop \ Crazy Programmer Work > python -u " c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py " Enter the Index at which you want to change value: 3 Enter the final value you want in list : 76 Traceback (most recent call last): File "c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py ", line 13, in <module> l1[index] = number TypeError: list indices must be integers or slices, not str |
In the above example, we have initialized a list of five numbers and we want to change the value of a particular index. We get out the index and value entered by the user and in the last operation, we are going to print the updated list. When we run the code and enter the respective value then we are getting the error. It states that the list indices must be integers or slices, not str it means that the index value we have passed in our code should be an integer.
We often make this mistake because we all know that the input function takes input as a string and if we want to use it as an integer then we have to convert it into an integer first, then we can use the index value and we will be able to perform our operation successfully.
Solution:
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# Declare a List l1 = [10, 20, 30, 40, 50] # Get Index input from User and convert it to integer index = int(input("Enter the Index at which you want to change value: ")) # Get the number from user number = int(input("Enter the final value you want in list : ")) # Update the value in list l1[index] = number # Print the list after updation print(f"Updated list is : {l1}") |
Output:
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PS C : \ Users \ ASUS \ Desktop \ Crazy Programmer Work > python -u " c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py " Enter the Index at which you want to change value: 3 Enter the final value you want in list : 76 Updated list is : [10, 20, 30, 76, 50] |
As we can see that after converting the index value into an integer, we are successfully able to perform the desired operation. We can see that the value at 4th index has been changed to 76.
Case 2:
We are given with a list of words and we want to create a new string with all the words from the list and create a proper sentence and then print it.
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# initialise a list of words list1 = ["This", "article", "is", "written", "by", "crazy", "programmer"] # initialise an empty string new_string = "" # initialist index with 0 index = 0 # run a loop through the list and add all the words in a string while index < len(list1): new_string = new_string + " " + list1[new_string] index = index + 1 # print the new combined words print(new_string) |
When we run our code then we will get some error.
Output:
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PS C : \ Users \ ASUS \ Desktop \ Crazy Programmer Work > python -u " c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py " Traceback (most recent call last): File "c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py ", line 70, in <module> new_string = new_string + " " + list1[new_string] TypeError: list indices must be integers or slices, not str |
Here the same error occurred. It means we have to re examine the index value passed to the list in our program. We have to make sure that the index value should be in an integer only, to run our code perfectly. In line 70 we can see that the index we have passed to our list is a string. At this point, many programmers does not realize the mistake in the code and they spend 1 to 2 hours in debugging it. In our program, we know that new_string is a string so we cannot pass it as an index. We have identified the error.
Solution:
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# initialize a list of words list1 = ["This", "article", "is", "written", "by", "crazy", "programmer"] # Initialize an empty string new_string = "" # initialize index with 0 index = 0 # run a loop through the list and add all the words in a string while index < len(list1): new_string = new_string + " " + list1[index] index = index + 1 # print the new combined words print(new_string) |
Output:
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PS C : \ Users \ ASUS \ Desktop \ Crazy Programmer Work > python -u " c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py " This article is written by crazy programmer |
We can see that our program is running successfully. We have fixed our code.
Conclusion
Whenever we see that error named TypeError: list indices must be integers or slices, not str. Then without making any changes in the code, firstly we have to figure out the uses of lists in our program, after that, we have to figure out where we are going to print the content of the lists or we are going to make any changes in the list.
If either of the cases is happening we have to check whether the index value passed in the list is an integer or not. It will give the error when the index value passed in the list is a string type. So we have to check it and fix it if it is not integer type.
