Asked By – Jordan Mack
I have the following piece of code which fails with the following error:
RuntimeError: maximum recursion depth exceeded
I attempted to rewrite this to allow for tail recursion optimization (TCO). I believe that this code should have been successful if a TCO had taken place.
def trisum(n, csum): if n == 0: return csum else: return trisum(n - 1, csum + n) print(trisum(1000, 0))
Should I conclude that Python does not do any type of TCO, or do I just need to define it differently?
Now we will see solution for issue: Does Python optimize tail recursion?
No, and it never will since Guido van Rossum prefers to be able to have proper tracebacks:
Tail Recursion Elimination (2009-04-22)
Final Words on Tail Calls (2009-04-27)
You can manually eliminate the recursion with a transformation like this:
>>> def trisum(n, csum): ... while True: # Change recursion to a while loop ... if n == 0: ... return csum ... n, csum = n - 1, csum + n # Update parameters instead of tail recursion >>> trisum(1000,0) 500500