Is there any difference between return and raise an Exception?

Question

Consider the following code:

def f(x):
    if x < 10:
        return Exception("error")
    else:
        raise Exception("error2")

if __name__ == "__main__":
    try:
        f(5)                        # f(20)
    except Exception:
        print str(Exception)

Is there any difference? When should I use return Exception and when should I use raise?

Answer 1

raise and return are two inherently different keywords.

---

raise, commonly known as throw in other languages, produces an error in the current level of the call-stack. You can catch a raised error by covering the area where the error might be raised in a try and handling that error in an except.

try:
    if something_bad:
        raise generate_exception()
except CertainException, e:
    do_something_to_handle_exception(e)

return on the other hand, returns a value to where the function was called from, so returning an exception usually is not the functionality you are looking for in a situation like this, since the exception itself is not the thing triggering the except it is instead the raiseing of the exception that triggers it.