The real reason for plus plus originally was that it made efficient use of the auto increment addressing modes on the PDP 11. Whether you use prefix or post fix now should be an issue of expressing what you mean. Worrying about the additional memory usage before you have even monitor the code is really a perfect example of Knuth’s “premature optimization is the root of all evil.”
The majority of your snippets are questionable re-implementations of methods that are available either on native Python types or in the Python standard library. While I applaud your desire to share your knowledge with others, in this case your teaching will only encourage bad programming habits.