when you run this programthe function gets defined when the def statement on line executes the next line of code that is executed is line kwhich calls passfortytwowhenyoucallthisfunction(and passes (gasp! as resultthe function calls itself on line and passes we call this call the recursive call this is what our program outputsstart of function you did not pass when you called this function fine will do it myself start of function thank you for passing when you called this function end of function end of function notice that the --start of function |and --end of function |text appears twice let' figure out what exactly happens and what order it happens in on line kthe function is called and is passed for the param parameter line prints out --start of function |the condition on line will be true (since ! so line and will print out their messages line will then make callrecursivelyto the function and passes for the param parameter so execution starts on line again and prints out --start of function |line ' condition this time is falseso it skips to line and finds that condition to be true this causes line to be called and displays --thank you |on the screen then the last line of the functionline iwill execute to print out --end of function |and the function returns to the line that called it but rememberthe line of code that called the function was line and in this original callparam was set to the code goes down to line and checks the conditionwhich is false (since = is falseso it skips the print(call on line insteadit runs the print(call on line which makes --end of function |display for second time since it has reached the end of the functionit returns to the line of code that called this function callwhich was line there are no more lines of code after line kso the program terminates note that local variables are not just local to the functionbut to specific call of the function stack overflows each time function is calledthe python interpreter remembers which line of code made the call that way when the function returns python knows where to resume the execution remembering this takes up tiny bit of memory this isn' normally big dealbut take look at this code