abcdcallstack pydef ()print(' (starts' ( (print(' (returns'def ()print(' (starts' (print(' (returns'def ()print(' (starts'print(' (returns'def ()print(' (starts'print(' (returns' (if you run this programthe output will look like thisa(starts (starts (starts (returns (returns (starts (returns (returns you can view the execution of this program at /abcdcallstackwhen (is called it calls (which in turn calls (the (function doesn' call anythingit just displays (starts and (returns before returning to the line in (that called it once execution returns to the code in (that called ()it returns to the line in (that called (the execution continues to the next line in the (function which is call to (like the (functionthe (function also doesn' call anything it just displays (starts and (returns before returning to the line in (that called it since (contains no other codethe execution returns to the line in (that called (the last line in (displays (returns before returning to the original (call at the end of the program the call stack is how python remembers where to return the execution after each function call the call stack isn' stored in variable in your programratherpython handles it behind the scenes when your program calls functionpython creates frame object on the top of the call stack frame