This is expected. Your timing measures the time for garbage collection of the large arrays in addition to the time for the result to be returned.

In the line `result = myfunc()`, the name `result` gets rebound to the value of `myfunc()`. That means that `result` is unbound from whatever it was previously bound to, and the old value then gets garbage collected.

You can test this by adding a "del result" line as the last line inside the "for" loop block.