I have a directory with several files which contain random unwanted characters in the filenames like:

027_blahblah.mp3
074blahblah3.txt

I would like to rmove (in bulk) specific characters in the file names so that after running the command the above would contain only characters:

blahblah.mp3
blahblah.txt

I am not scripting proficient but would like to be.
If anyone has recommendations for a good perl or python tutorial it would be much appreciated.
Thanks for any assistance with this!!

First, exactly what characters would you like to remove or change ? I see an _ and numbers, anything else ? In fact it may be more prudent to say what characters to keep instead.

As an example I have a script that fixes names so they all are lowercase and removes spaces and illegal characters (or rather keeps good ones):

this happens for all files in the directory, but instead of '*' you could put '*.mp3' for all mp3s in the directory. However, I think you might want to customize it.

Maybe you should post a few actual filenames. Regex expressions can be very exacting, and "for instance" examples you make up of the top of your head may convey the actual pattern to use. Also, are the number of preceding characters the same? Do they all have the `_' character separating the random characters at the beginning from the filename?

1234_filename.ext
Using ${filename#*_} will remove the characters you want that use this pattern.
12-qqfilename.ext
Using ${filename#?????} will remove the characters for this type of pattern by simply removing the first 5 characters.

You also need to be careful if after removing the characters, the filenames are no longer unique.
1234_picture1.jpg
4321_picture1.jpg

Then run 'mv -i' to make it interactive or use '--backup' option to prevent clobbering.