fruitful functions and void functions some of the functions we are usingsuch as the math functionsyield resultsfor lack of better namei call them fruitful functions other functionslike print_twiceperform an action but don' return value they are called void functions when you call fruitful functionyou almost always want to do something with the resultfor exampleyou might assign it to variable or use it as part of an expressionx math cos(radiansgolden (math sqrt( when you call function in interactive modepython displays the resultmath sqrt( but in scriptif you call fruitful function and do not store the result of the function in variablethe return value vanishes into the mistmath sqrt( this script computes the square root of but since it doesn' store the result in variable or display the resultit is not very useful void functions might display something on the screen or have some other effectbut they don' have return value if you try to assign the result to variableyou get special value called none result print_twice('bing'bing bing print(resultnone the value none is not the same as the string "noneit is special value that has its own typeprint(type(none)to return result from functionwe use the return statement in our function for examplewe could make very simple function called addtwo that adds two numbers together and returns result