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in Python

I have this tail-recursive function here:

def fib(n, sum):

if n < 1:

return sum

else:

return fib(n-1, sum+n)

c = 998

print(fib(c, 0))

It works up to n=997, then it just breaks and spits a "maximum recursion depth exceeded in comparison" `RuntimeError`. Is this just a stack overflow? Is there a way to get around it?

by (16.8k points)

It is a guard against a stack overflow, yes. Python (or rather, the CPython implementation) doesn't optimize tail recursion, and unbridled recursion causes stack overflows. You can change the recursion limit with `sys.setrecursionlimit`, but doing so is dangerous -- the standard limit is a little conservative, but Python stackframes can be quite big.

Python isn't a functional language and tail recursion is not a particularly efficient technique. Rewriting the algorithm iteratively, if possible, is generally a better idea.

by (20.3k points)

It seems like you just need to set a higher recursion depth like this:

sys.setrecursionlimit(1500)