Modifying existing regex

Question

I have the existing regex:

self.metadata = re.sub('(?<=<file_name>)\d{4,}','', self.metadata)

This will do the following conversion:

<file_name>1232434_FILE.mov --> <file_name>FILE.mov

However, I do not want it to strip a filename if there is a . (period) directly after it.

So, the result should be:

<file_name>1232434_FILE.mov --> <file_name>FILE.mov
<file_name>123445.mov --> <file_name>123445.mov

What would be the new correct regular expression to use?

zessx · Accepted Answer · 2014-05-20 18:25:47Z

2

You should add a lookahead :

self.metadata = re.sub('(?<=<file_name>)\d{4,}(?![.\d])','', self.metadata)

<file_name>1232434_FILE.mov => <file_name>_FILE.mov
<file_name>1232434FILE.mov  => <file_name>FILE.mov
<file_name>123445.mov       => <file_name>123445.mov

Regular expression visualization

Debuggex Demo

answered May 20, 2014 at 18:25

zessx

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1 Comment

Sam Over a year ago

Lol, I guess a negative lookahead makes more sense than a lookahead with a negatiave character class +1

Sam · Accepted Answer · 2014-05-20 18:25:10Z

0

Add a lookahead to assert that your file name is followed by a non-digit, non . character. Note, we can't just look for a non . character, because that could be your 5th digit (since we match 4+ digits).

self.metadata = re.sub('(?<=<file_name>)\d{4,}(?=[^\d.])','', self.metadata)

RegEx

(?<=<file_name>)\d{4,}(?=[^\d.])

Note, this will replace <file_name>1232434_FILE.mov to <file_name>_FILE.mov but your current solution does that as well..

answered May 20, 2014 at 18:25

Sam

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