[Tutor] Flow control question.

[Clay Shirky]

As an exercise, I am writing a MAC address tester. It takes a collection of
possible MAC addresses, compares them to a test case, and outputs matches,
doesn't match, and errors for strings that cant be valid MAC addresses.

On these errors, I return with 0, then, in the "check addresses" loop, I try
to 'continue' if the return value is 0, but it isn't working.

The code is

def bad_address(address, error):
    print address, "not a valid MAC address:", error, "..."

def test_mac(mac):
    address_list = []
    elements = re.split('[\:\-\.]', mac)
    if len(elements) == 1:
        bad_address( mac, "No valid seperator...")
        return 0
    if len(elements) != 6:
        bad_address( mac, "Need 6 two-hex-digit numbers...")
        return 0
        
    for element in elements:
        num = long(element, 16)
        if num >= 256:
            bad_address(mac, "Numeric element above 256")
            return 0
        else:
            address_list.append(element)
            
    hex_num = "".join(address_list)
    return long(hex_num, 16)

    
for new_address in new_addresses:
    if new_address == 0: continue # I want to skip the next test
    if test_mac(new_address) == test_mac(orig_address):
        print new_address, "matches", orig_address
    else:
        print new_address, "doesn't match..."

And when I run it against a test list, every address that fails generates
two errors, both a bad_address() error and a "doesn't match" error from the
for loop below.

How can I make the for loop skip the second if test if the return is after a
bad_address() call?

-clay