[Tutor] recursion depth

[Emile van Sebille]

On 1/8/2014 12:25 PM, Keith Winston wrote:
> I've been playing with recursion, it's very satisfying.
>
> However, it appears that even if I sys.setrecursionlimit(100000), it
> blows up at about 24,000 (appears to reset IDLE). I guess there must be
> a lot of overhead with recursion, if only 24k times are killing my memory?

Yes -- the docs warn specifically about that:

sys.setrecursionlimit(limit)¶
Set the maximum depth of the Python interpreter stack to limit. This 
limit prevents infinite recursion from causing an overflow of the C 
stack and crashing Python.

The highest possible limit is platform-dependent. A user may need to set 
the limit higher when she has a program that requires deep recursion and 
a platform that supports a higher limit. This should be done with care, 
because a too-high limit can lead to a crash.


> I'm playing with a challenge a friend gave me: add each number, up to
> 1000, with it's reverse, continuing the process until you've got a
> palindrome number. Then report back the number of iterations it takes.
> There's one number, 196, that never returns, so I skip it. It's a
> perfect place to practice recursion (I do it in the adding part, and the
> palindrome checking part), but apparently I can't help but blow up my
> machine...

Without seeing your code it's hard to be specific, but it's obvious 
you'll need to rethink your approach.  :)

Emile