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In Common Lisp we can use macros to bring about a reasonable tail calling system without relying on TCO support in the implementation.

In the Lisp source file below, I provide a tlet operator whose syntax resembles labels, but which compiled to a tagbody in which the "functions" are just labels.

There is also deftail for tail calling among global functions, which is based on dynamic non-local returns and a dispatch mechanism.

http://www.kylheku.com/cgit/lisp-snippets/tree/tail-recursio...

Really fantastic point. I'm not a heavy user of Python. But, when I need to quickly prototype something its simplicity - i.e. one good way to do something, although this is a little exaggerated - makes the development very quick. Given my late start with Python, I work only in 3.x so I don't even need to look at search results with 2.x solutions in them: the range of solutions is narrowed further.

> If you are going to require high-performance

I'm not sure exactly why people bring up performance when tail call elimination is mentioned. Maybe because sometimes it's called "tail call optimization"? Besides replacing a call with a jump, it's more of an "optimization" in the sense that it allows an optimizing compiler to see and optimize a loop. However, CPython is not an optimizing compiler, and it would barely be an optimization.

Rather, tail call elimination is a feature that allows for a very controlled goto statement, and even a computed goto. However, "continue" and "break" seem to work well enough for most cases. Perhaps the strongest objection to having TCO is that stack traces become more inscrutable.

>I'm not sure exactly why people bring up performance when tail call elimination is mentioned.

Yes, you are correct, however i was mentioning TCO and performance as separate topics. This nonwithstanding, consider that TCO allows writing recursive functions without utilizing call stack space, and this might have some performance impact as well.

> There's also the case of some of those potential features threatening to go against the Zen of Python

It seems like "Zen of Python" is applied inconsistently, especially the "one way to do it" rule. Python is horrid about "one way to do it"--list comprehensions vs loops, decorator syntax vs `x = decorate(x)`, try/except/finally vs with, etc etc. In particular, if we are going to force a choice between iterative and recursive based on "one way to do it", then I would vote recursion + tco. Of course, this is a false dichotomy and we could have the best of both worlds.

> if you are going to require high-performance * , or things that collide with the Global Interpreter Lock, etc, then simply Python is not the best choice.

Unfortunately, people rarely realize their performance requirements until they're neck-deep in Python. Basically if you ever, ever, ever think you might need decent performance, there are performant languages that beat Python at its own friendliness/maintainability game (Go comes to mind).

I don't see a conflict between loops, list comprehensions and other shortcuts - use the syntax sugar where it makes the code simpler/easier to read, otherwise stick to plain loops.

My own rules for "list/dict comprehension" versus "loops" versus "generator expressions" are the following:

* use a loop where you are interested only in the side-effects or where it will make the code easier to read

* use generator expressions where you don't really need to instantiate a list, for example when you are just iterating over the result and throwing it away.

* use list or dict comprehensions where you need to build and save a list/dict and the resulting code does not resemble a lisp program (where the choice does not make the program harder to read).

I agree, but it's nevertheless a violation of the "one obvious way" rule.

It seems like "Zen of Python" is applied inconsistently

Good. I think we would all be better off if we forgot about it entirely.