Generator Pipelines and Reuse

Understanding why chained generators over large datasets can be silently exhausted after one pass.

You build a memory-efficient pipeline over a huge log file: ```python lines = (line.strip() for line in open('huge.log')) errors = (l for l in lines if 'ERROR' in l) total = sum(1 for _ in errors) first_five = list(errors)[:5] ``` Why is `first_five` an empty list?