The code below implements the functionality described in
Section 5, “The
Singleton base class: A classic design pattern”. The code is kept in a
singleton.py, and not in the
file, because it may be useful elsewhere.
A Python implementation of the Singleton pattern is given on page 84 of this work:
Martelli, Alex. Python in a nutshell. O'Reilly, 2003, 1st ed., ISBN 0-596-00188-6.
The present work is basically an elaboration of that code with literate annotation.