fig the run-time stack of recursive function call each time the function is called new activation record is pushed and new copy of the local variables is stored within the activation record the picture in fig depicts the run-time stack at its deepest point when execution of the function gets to the point when equals the python interpreter finds that equals on line of the code it is at this point that the sumfirstn function returns its first value it returns to the previous function call where was the return occurs on line of the code the activation record for the function call when was is popped from the run-time stack this is depicted in fig by the shading of the activation record in the figure when the function returns the space for the activation record is reclaimed for use later the shaded this copy belongs to 'acha