You are analyzing a log file with transaction data. Positive values represent sales, while negative values represent refunds. Your task is to process the data efficiently using generator functions and expressions.
Each line in the log file is formatted as follows:
date, user_id, transaction_amount
For example:
2025-01-20 12:00:00,user_123,50.75
2025-01-20 12:01:00,user_456,20.00
2025-01-20 12:02:00,user_123,-10.50
