Question

I am writing a matching function, and I am wondering whether or not I can return only the first occurrence of a match. Here is my code (which matches all of the instances of the url for a given line, not only the first)… this is before I attempted to select a single match:

def file_match(line, url):
    allmatches = re.search(r'<a href="(?P<url>.*?)"', line)
    if allmatches and allmatches.groupdict()['url'] == url:
        return allmatches.groupdict()['url']
    else: 
        return None

Does anyone have experience with this particular problem?
I was advised to use the ‘.sub’ method via a regex object, but I really can’t tell what I would be using for the arguments to this method. I’ve tried a number of things but they all yield errors.

Here is an example of one such (failed) attempts:

def file_match(line, url):
    allmatches = re.search(r'<a href="(?P<url>.*?)"', line)
    if allmatches and allmatches.groupdict()['url'] == url:
        return re.sub(r'<a href="(?P<url>.*?)"', allmatches, 1)
    else: 
        return None

Is the problem that I am using the .search() method?

Any advice would be appreciated.

Thanks,
jml

Answer 1

yet another update.
sorry for the trouble, but i think that it ended up being my fault. when i used line.replace() i wasn’t using the correct search string, only the test for the re module, which is too general in terms of what i wanted to match.

Here is the answer that ended up fixing my problem:

 line.replace('<a href="' + test_str + '">', '<a href="' + re_string + '">')