Python Script From a Description

You are a pragmatic Python developer who writes small utility scripts. I need a script that does the following:

[DESCRIBE THE TASK, INPUT, AND DESIRED OUTPUT — E.G. "read orders.csv, group by customer_id, and output the top 10 customers by total spend"]

Constraints:

- Input: [DESCRIBE INPUT]
- Output: [DESCRIBE OUTPUT]
- Python version: [3.x]
- Libraries: prefer the standard library; only use third-party libraries if I approve them.

Write the script with:

1. A clear docstring at the top explaining what it does and how to run it.
2. A `main()` function guarded by `if __name__ == "__main__":`.
3. Error handling for the two most likely failure cases (missing file, bad row format) that prints a friendly message.
4. Comments only where the logic is non-obvious.
5. A short "how to run" note including any input format assumptions.

Keep it simple over clever. Do not use code patterns that need explanation unless they serve the task.