os.rename() problems on OS X

[lukas]

hello,

i recently had the job of having to rename about 200 files. The source
for the renaming was a bunch of names in a file. I know next to
nothing when it comes to bash scripting (which would have seemed the
obvious choice) so i used python. The files i was renaming were canon
raw files (.CR2). my problem is that after i rename the files, OS X
will no longer render the thumbnails for the files, and preview is no
longer the default app for viewing them. Does anyone have an idea as
to why this is? Thanks for the help :)

-Lukas