Using Regex to Find and Replace

Question

I would like to take a text document that contains Feet+Frames values and convert them to Timecodes. For example, 0000+00 is replaced with 00:00:00:00.

I have a function to do the conversion from Feet+Frames to Timecode (16 frames per foot, framerate is 24 frames per second):

def FeetFramesToTimecode(FeetFrames):
    frames = int(FeetFrames[:4])*16+int(FeetFrames[-2:])
    return "%02d:%02d:%02d:%02d" % (frames/(3600*framerate), frames/(60*framerate)%60, frames/framerate%60, frames%framerate)

And then I have code that goes through the text file and sub's the Feet+Frame with timecode:

for line in input_document:
    found = re.search(r'\d{4}\+\d{2}', line)
    if found:
        print "%s replaces %s" % (FeetFramesToTimecode(found.group()), found.group())
        new_line = re.sub(r'\d{4}\+\d{2}', (FeetFramesToTimecode(found.group()), line)
        output_document.write(new_line)
    else:
        output_document.write(line)

So, what am I doing wrong? How do I get a function to work inside of a re.sub?

stylistically - please save CamelCase for classes and use words_separated_by_underscores for function names. (i.e. def feet_frames_to_time_code(feet_frames)). This makes it much clearer what is going on. (Notice how your question highlights the CamelCase differently then the rest of the code?) — Jeff Tratner
– Jeff Tratner, Commented Jun 7, 2013 at 3:19
I learned a new word today... CamelCase. As I said, I don't know much about programming... much less what a class is. I'm learning though and appreciate the input. — Paul Carlin
– Paul Carlin, Commented Jun 7, 2013 at 18:37
Well, if you learned it, may as well say that that’s PascalCase, not camelCase. =) — Ry-
– Ry- ♦, Commented Jun 8, 2013 at 1:48

Phil Cooper · Accepted Answer · 2013-06-07 03:32:29Z

1

resub can take a second argument of a callable rather than just the replacement string.

If you pass a callable, it must take the match object.

You should also follow the python pep8 to make the python more readable (for other pythonistas)

Something like:

def feetframes_to_timecode(feetframes_match, framerate=24):
    feetframes = feetframes_match.group()
    frames = int(feetframes[:4])*16+int(feetframes[-2:])
    return "%02d:%02d:%02d:%02d" % (frames/(3600*framerate),
                                    frames/(60*framerate)%60,
                                    frames/framerate%60,
                                    frames%framerate)
# then just use:
for line in input_document:
    output_document.write(re.sub(r'\d{4}\+\d\d', feetframes_to_timecode, line))

edited Jun 7, 2013 at 3:32

answered Jun 7, 2013 at 3:22

Phil Cooper

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2 Comments

Paul Carlin Over a year ago

I apologize for my bad scripting as I have no formal education on this topic. I simply have an idea and Google my way to the final script. I will take a look at whatever pep8 is and try to improve my formatting. Thanks for all your help on this!

Paul Carlin Over a year ago

Ahhh! I see! Move the match.group() to the function instead! That's a good idea.

cforbish · Accepted Answer · 2013-06-07 03:09:29Z

0

Your example code has an extra '(' that does not belong. This is what the line should be:

new_line = re.sub(r'\d{4}\+\d{2}', FeetFramesToTimecode(found.group()), line)

This produced output for me like you want.

answered Jun 7, 2013 at 3:09

cforbish

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1 Comment

Paul Carlin Over a year ago

Doh! I feel like Homer on this one. Thanks for pointing this out.

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