Explain to me what the big deal with tail call optimization is and why Python needs it

Personally, I put great value on tail call optimization; but mainly because it makes recursion as efficient as iteration (or makes iteration a subset of recursion). In minimalistic languages you get huge expressive power without sacrificing performance.

In a 'practical' language (like Python), OTOH, you usually have a lot of other constructions for almost every situation imaginable, so it's less critical. It is always a good thing to have, to allow for unforeseen situations, of course.

Personally, I put great value on tail call optimization; but mainly because it makes recursion as efficient as iteration (or makes iteration a subset of recursion). In minimalistic languages you get huge expressive power without sacrificing performance.

In a 'practical' language (like Python), OTOH, you usually have a lot of other constructions for almost every situation imaginable, so it's less critical. It is always a good thing to have, to allow for unforeseen situations, of course.

If you intensely want to use recursion for things that might alternatively be expressed as loops, then "tail call optimization" is really a must. However, Guido, Python's Benevolent Dictator For Life (BDFL), strongly believes in loops being expressed as loops -- so he's not going to special-case tail calls (sacrificing stack-trace dumps and debugging regularity).

Tail call optimization makes it easier to write recursive functions without worrying about a stack overflow:

def fac(n, result=1):
        if n > 1:
                return fac(n - 1, n * result)
        return result

Without tail call optimization, calling this with a big number could overflow the stack.