The other day I set out to use BASH to mass rename, and I had such trouble backslash-escaping the dot characters and whitespaces to prevent sed from interpreting them specially. Eventually I gave up and searched for the pythonic way to rename them, and it was as simple as a string replacement followed by a call to os.rename() inside a for-loop. It was a breath of fresh air to escape “command line Kung Fu” and fearing the thrashing from shell globbing.
To be fair, I got my start in using sed and awk as powertools in the BASH command pipeline, but I don’t miss them compared to a language with strong data types and simple built-in methods for handling complex manipulation. Python is built in to basically every Linux distro that has BASH, and for the sake of simple transformations, it offers a lot of succinct methods that work on either 2.7 or 3.x with no external packages.
But if you're dealing with changing stuff in text files greater than 25 gigs I'd always recommend using the unix cmd line tool set for simple modifications if performance is a key concern. It works the same everywhere and can rip through big files. But I'm a Vim guy and I live in the shell so I'm surely quite biased lol.
There are plenty of pretty easy one liners though that can rename files depending on if you can define a pattern correctly though.
echo 'TV Show Name 2014.L337.H4XXX1080p-420.mkv' | awk -F . -v q="'" '{print q$0q" "q$1".mkv"q }' | xargs mv
find . -type f -name '*.mkv' -printf '%f' | awk -F . -v q="'" '{print q$0q" "q$1".mkv"q}' | xargs mv
Once things get complicated though you should probably push whatever transformations you need to do to a database.