Is there a way to check if function is recursive in python?

Question

I want to write a testing function for an exercise, to make sure a function is implemented correctly.
So I got to wonder, is there a way, given a function \"foo\", to ch

Answer 1

I have not yet verified for myself if Alex's answer works (though I assume it does, and far better than what I'm about to propose), but if you want something a little simpler (and smaller) than that, you can simply use sys.getrecursionlimit() to error it out manually, then check for that within a function. For example, this is what I wrote for a recursion verification of my own:

import sys

def is_recursive(function, *args):
  try:
    # Calls the function with arguments
    function(sys.getrecursionlimit()+1, *args)
  # Catches RecursionError instances (means function is recursive)
  except RecursionError:
    return True
  # Catches everything else (may not mean function isn't recursive,
  # but it means we probably have a bug somewhere else in the code)
  except:
    return False
  # Return False if it didn't error out (means function isn't recursive)
  return False

While it may be less elegant (and more faulty in some instances), this is far smaller than Alex's code and works reasonably well for most instances. The main drawback here is that with this approach, you're making your computer process through every recursion the function goes through until reaching the recursion limit. I suggest temporarily changing the recursion limit with sys.setrecursionlimit() while using this code to minimize the time taken to process through the recursions, like so:

sys.setrecursionlimit(10)
if is_recursive(my_func, ...):
  # do stuff
else:
  # do other stuff
sys.setrecursionlimit(1000) # 1000 is the default recursion limit