<---- start code ----> import itertools data = """Line1 Line2 Line4 Line5""" def test_to_start(s): return "2" in s for line in itertools.dropwhile(test_to_start, data.splitlines()): print(line) <---- end code ----> I expect: $ python3 dropwhile.py Line2 Line4 Line5 I get: $ python3 dropwhile.py Line1 Line2 Line4 Line5 Please explain.