I keep it in my home directory and from any directory (MacOS) I can run it via the command:
~/image2htm.py
A file named images.htm will remain in the current directory. Open it to see the images in that directory.
I've hard-coded the output filename and the width style attribute. These are easy enough to change in the code.
Things I learned: I had no idea until working on this script that the endswith() method can use a tuple of comparator strings.