Efficient character escapes decoding

I ran into this technical issue using Python's 'unicode_escape' codecs on unicode string. Put a question in the comp.lang.python newsgroup and thought this is probably too technical for anyone to care. But the Python community never fails me. Thank you for Steven Bethard to come up with a great suggestion that works for me. I have written up the solution in a Python cookbook recipe.

Hope it will be useful for other people too.