Help creating a pattern using the re module

[zulu_likuum]

What's your code for the two-pass solution?

You mention that the 4th should not be renamed, but you actually remove a space. It might be good to clarify which it is.

Wow. I knew something was different. I couldn't find a way to edit my post, so allow me to correct it here.

I have written a python3 script to rename files based on a pattern input by the user. It has worked well, but I now am trying to create a pattern, and I am running into problems.

Correction:

I have four types of filenames:
filename1 - flubber.MP4
filename2.MP4
filename3 - flubber.mp4
filename4.mp4

I am trying to create a pattern that will work on all these file names and rename them all as:
filename1.mp4
filename2.mp4
filename3.mp4
filename4.mp4 (This one of course would not be renamed)

I can easily accomplish this in two passes, but I would like to accomplish it in one pass. Help?

---

How do you easily accomplish this in two passes?

See my correction in response to micseydel.

My two-pass solution is:
1st pattern:
(.+)MP4$
Replacement:
\1mp4

2nd pattern:
(.+) - flubber(.+)
Replacement:
\1\2