Python: Find the index of the last element in the given list that satisfies a testing function

Last update on April 19 2025 13:01:03 (UTC/GMT +8 hours)

Last Index Satisfying Function

Write a Python program to find the index of the last element in the given list that satisfies the provided testing function.

Sample Solution:

Python Code:

# Define a function 'find_last_index' that takes a list 'lst' and a function 'fn' as input.
def find_last_index(lst, fn):
    # Reverse the 'lst', enumerate it, and find the first index where the function 'fn' returns 'True' in the reversed list.
    # Then, subtract the found index from the length of the list to get the last index where 'fn' returned 'True' in the original list.
    return len(lst) - 1 - next(i for i, x in enumerate(lst[::-1]) if fn(x))

# Call the 'find_last_index' function with an example list and a lambda function 'fn', and print the result.
print(find_last_index([1, 2, 3, 4], lambda n: n % 2 == 1))

Sample Output:

2

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to find the index of the last element in a list that meets a provided condition.
• Write a Python program to retrieve the last index where an element is negative using a lambda function.
• Write a Python program to determine the last index of an element that satisfies a custom test, returning -1 if none qualify.
• Write a Python program to find the last index in a list where the square of the element is greater than a specified value.

Python Code Editor:

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