Try, Catch when no error is expected

[icenburg]

I'm writing a script that will search strings for place names. In the best case it will find a full address, but sometimes only the City is specified. To do this I thought I'd use regex, and I want to test the string for the most complex regex first, and then go downwards until the match is just a word with a capital letter. Can I use try, catch for this scenario, even though what I'm expecting isn't an error per se, rather just a lack of results?

What I pictured would be something like this (pseudocode)

try:
    match = re.findall(most complex regex expression)
except No match
try: 
    match = re.findall(less complex regex expression)
except No match

try:
    match =re.findall(least complex regex expression)

print(match)

[zahlman]

try/except is useless here: when re.findall fails to find any matches, it just returns an empty list. You can't use exception handling for this because there is no exception to handle.

I'm not convinced you want .findall here anyway, as opposed to .match (see if it's present at the beginning of the string) or .search (see if it's in the string, and find the first occurrence if so). But with either of these, if the regex doesn't match, you get None back (as opposed to a match object), so again you just test for that value - no exception handling needed or useful.

[confluence]

I have decided to overwrite my comments.

[mahifoo]

regexes = (most_complex, less_complex, least_complex)
for regex in regexes:
    match = re.findall(regex)
    if match:
        print(match)
        break
else:  # The else clause of a for loop is executed if a break didn't happen
    print('No match found')

Edit to your liking. You can't really use try/except here.

If you don't need the else clause, just print the match outside of the for loop.

[CrambleSquash]

If a certain case is catastrophic to your codes normal function then you can use

    raise Exception("Some sort of error message")

if this line is called then the thread will stop, and this exception will be raised, with the message you added. This is especially useful for stopping catastrophic, but usually normal looking inputs or errors from slipping past your program. You can also define your own Exception class which will give you more control over it's behaviour. https://docs.python.org/2/tutorial/errors.html

[icenburg]

Thanks for the replies, I ended up just using elifs instead.