Handling IndexError Exception in Python list operation program

Last update on March 29 2025 13:01:06 (UTC/GMT +8 hours)

6. Handle IndexError in List Operations

Write a Python program that executes an operation on a list and handles an IndexError exception if the index is out of range.

exception IndexError:

Raised when a sequence subscript is out of range. (Slice indices are silently truncated to fall in the allowed range; if an index is not an integer, TypeError is raised.)

Sample Solution:

Code:

# Define a function named test_index that takes 'data' and 'index' as parameters.
def test_index(data, index):
    try:
        # Try to access an element at the specified 'index' in the 'data' list and store it in the 'result' variable.
        result = data[index]
        # Perform desired operation using the result (in this case, printing it).
        print("Result:", result)
    except IndexError:
        # Handle the exception if the specified 'index' is out of range for the 'data' list.
        print("Error: Index out of range.")

# Define a list of numbers 'nums'.
nums = [1, 2, 3, 4, 5, 6, 7]
# Prompt the user to input an index and store it in the 'index' variable.
index = int(input("Input the index: "))
# Call the test_index function with the 'nums' list and the user-provided 'index'.
test_index(nums, index)

Explanation:

In the above exercise,

• The "perform_operation()" function takes two parameters: data, which represents the list, and index, which represents the index of the element.
• Inside the function, we use a try block to access the element at the specified index in the list. If the index is within the list range, the element is assigned to the result variable.
• We can then execute the desired operation using the result. In this example, we simply print the result.
• If the index is out of range and an IndexError exception occurs, the program jumps to the except block.
• In the except block, we catch the IndexError exception and print an error message indicating that the index is out of range.

Output:

Input the index: 0
Result: 1

Input the index: 4
Result: 5

Input the index: 9
Error: Index out of range.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program that attempts to access an element beyond the list length and catches the IndexError to print a custom message.
• Write a Python program to implement a function that safely retrieves an element from a list given an index, returning a default value if out of range.
• Write a Python program to iterate over a list using a for-loop and handle IndexError when accessing a specific index in a try-except block.
• Write a Python program to demonstrate IndexError by intentionally accessing an invalid index and then using a fallback mechanism to avoid crashing.

Python Code Editor:

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