Python error message

It looks to me like too much recursion.

Each method invocation requires a frame which is stored in the memory reserved for stack. If your stack gets large enough to use all available stack memory, then any attempts to use additional stack space will fail with an unpredictable crash, like the one you're seeing.

This kind of crash often occurs with infinite recursion, but given how heavily your program appears to rely heavily on recursion, you may simply be attempting to recurse too much for larger inputs. You might want to try using a simple loop instead.

 

The stack holds important information. If it's purged, you lose information. That isn't something a program usually does intentionally.

The standard way of avoiding death by recursion is to refactor it so the recursive structure is explicit. That is, implement your own stack. This usually takes less memory than relying on the call stack, but it will still have a recursion limit. It also gives you the control necessary to virtualize it to disk if necessary.

The other tool to apply is converting tail-recursion to iteration. Search Wikipedia for keywords tail recursion.

 

There was a good bit of discussion on this (albeit for C not python, but the general ideas still apply) here:
http://forums.macrumors.com/showthread.php?t=561251

-Lee