Well... string parsing is always going to be be a bit of a crapshoot.
Especially if you're trying to come up with something like parsing out the
framenumbers, for a very general case, there will always be things that
break it. In general, it's best if you can enforce some sort of uniformity
on your filenames, so you can have a certain amount of assurance that it's
going to work as intended.
However - to your specific regex - if you're looking specifically to catch
cases that look like:
filename.####.ext
filename_####.ext.
...you're on the right track, but there's a few things I would fix.
First, some general advice - ALWAYS get in the habit of prefixing your
regex pattern strings with "r", like: r'myPattern'
The 'r' marks it as a raw string, meaning backslashes aren't treated as
escape sequences. Since python keeps the backslash for sequences it
doesn't recognize, MOST of the time it won't make a difference, but it's
best to just get in the habit now. I also like to always triple quote my
regex patterns, for cases when I need to search for a quote mark...
Second - you probably want to make sure that your expression only matches
at the END of the string - easiest way to do that is with a "$" character
at the end. otherwise, if your file is:
f = "myawesome_filename_ver_1_frame.0001.exr"
...you'll get the wrong result. Also, I wouldn't limit your file
extensions to only 3 characters - ".jpeg" and ".tiff" pop up pretty
frequently. So at least allow 4 characters (and possibly just make it 1+).
Finally, you'll probably want to start using groups - at minimum, around
the framenumbers. So my final take would look something like:
pat = re.compile*(r'''[.|_](\d+)\.(\w{3,4})$''')*
print pat.search(f).groups()
If you want to get fancy, python regular expressions allow you to name your
groups, which I like. The main downside is that this is a python only
extension, so if you try to copy your regex somewhere else, it won't work:
pat = re.compile*(r'''[.|_](?P<frame>\d+)\.(?P<ext>\w{3,4})$''')*
print pat.search(f).groupdict()
- Paul
PS - Is that Kurt Russel from "The Thing", or do you just happen to look
just like him? Either way, it's awesome...
On Wed, Jul 30, 2014 at 12:03 PM, md <[email protected]> wrote:
> Hey guys,
>
> I am fairly new to regular expressions.
>
> When I want to get the delimiter between a filename and framenumber I am
> using the following regex.
>
> f = myawesome_filename_v1_0001.exr"
>
> pat = re.compile*('[\.|\_]\d+[\.]\w{3}')*
> x = re.search(pat, f)
> print x.group()
> delimiter = x.group()[0]
> print 'delimiter : ' + delimiter
>
> This works specifically for the case where you might have
> filename.####.ext or filename_####.ext.
>
> Question is ... is this a decent/efficient way to do this ?
>
>
>
>
>
>
>
>
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