import traceback try: a = {'123': 4} b = a[6] except KeyError: actual = traceback.format_exc() expected = '''Traceback (most recent call last): File "tests/80_traceback.py", line 5 b = a[6] KeyError: 6''' if actual != expected: print('--- ACTUAL RESULT -----') print(actual) print('--- EXPECTED RESULT ---') print(expected) exit(1)