Python - Add "Key" to csv game script

import csv
import os

def update_csv_keys(file_path):
    try:
        # Extract the filename without extension for key generation
        filename = os.path.splitext(os.path.basename(file_path))[0]

        with open(file_path, mode='r', newline='') as file:
            # Reading the CSV file
            reader = csv.DictReader(file)
            rows = list(reader)

        # Clear existing content in the "Key" column
        for row in rows:
            row['Key'] = ''

        # Index for key generation
        key_index = 1
        added_keys = []

        # Update rows
        for row in rows:
            if row['Line']:  # Check if 'Line' column is not empty
                new_key = f'{filename}_{key_index}'
                row['Key'] = new_key
                added_keys.append(new_key)
                key_index += 1

        with open(file_path, mode='w', newline='') as file:
            # Writing back to the CSV file
            fieldnames = reader.fieldnames
            writer = csv.DictWriter(file, fieldnames=fieldnames)
            writer.writeheader()
            writer.writerows(rows)

        return added_keys

    except Exception as e:
        return f"An error occurred: {e}"

# Ask for the CSV file path
file_path = input("Enter the path to the CSV file: ")
result = update_csv_keys(file_path)

# Check if the result is an error message or keys
if isinstance(result, list):
    # Print all added keys
    print("\nAdded keys:")
    for key in result:
        print(key)
    print("\nCSV file has been updated.")
else:
    # Print the error message
    print(result)