Find if error occured in function's try/except block

Question

I want to test the format of multiple dates using this function, then use sys.exit(1) to exit after all the checks are done if any of them returned an error. How can I return if any of multiple checks had an error?

def test_date_format(date_string):
    try:
        datetime.strptime(date_string, '%Y%m')
    except ValueError:
        logger.error()

test_date_format("201701")
test_date_format("201702")
test_date_format("201799")

# if any of the three tests had error, sys.exit(1)

Answer 1

You could return some indicator:

def test_date_format(date_string):
    try:
        datetime.strptime(date_string, '%Y%m')
        return True
    except ValueError:
        logger.error()
        return False

error_happened = False # Not strictly needed, but makes the code neater IMHO
error_happened |= test_date_format("201701")
error_happened |= test_date_format("201702")
error_happened |= test_date_format("201799")

if error_happened:
    logger.error("oh no!")
    sys.exit(1)

Answer 2

First of all, lets assume you have the datestring as list/tuple. ie datestring_list = ["201701", "201702", "201799"]. So the code snippet are as follows...

datestring_list = ["201701", "201702", "201799"]

def test_date_format(date_string):
    try:
        datetime.strptime(date_string, '%Y%m')
        return True
    except ValueError:
        logger.error('Failed for error at %s', date_string)
        return False

if not all([test_date_format(ds) for ds in datestring_list]):
    sys.exit(1)