Return Values - CS50P Shorts

Key Takeaways

[Music] well hello one and all and Welcome to our short on return values so let's say I want to find the area of my apartment how much square fet is inside of it well I know my apartment is about 50 ft wide and about let's say 20 ft long so to find the area of my apartment I could multiply these two numbers together to get the total area inside in terms of square F feet so I wrote a program here to do just that I have a function here called area that takes in two parameters length and width what I'll then do is print the result of multiplying length time width converted of course to a string and I'll concatenate this result with the other string square feet so let's try this out uh here in my main function I'm calling area with two particular arguments 50 and 20 and I should get let's say about 1,000 squ ft I'll run python of area. Pi hit enter and I will see 1,000 square ft so area seems to working just as I want it to now let's imagine I had maybe more space to add to my apartment maybe I also have a yard I want to figure out how much space I have in my yard too well let's visualize that first back here I have my apartment but let's say I added on some space for a yard well in this case my yard is is 50 ft wide and 50 ft long so I need to multiply those two values together to find the area of my yard well I'll go back to my program here and because I have this area function I could just call it again with different arguments so down here on line 7even let's say I'll run area and provide 50 for the length and 50 for the width and now if I run python of area. Pi I'll see the area for my house and the area for my yard well this is all well and good but what if I wanted to add these two numbers together maybe I want to find the total area between my house and my yard well currently I actually can't do that and that's because area doesn't have what we would call a return value at least one that I can use right now in my program so here area really only has we would call a side effect something that changes as a result of this function running in this case we see down below some text being printed to the screen and that makes sense because on line two we call the print function whose side effect is to print something to my terminal down below but if I look in this main function here where I call both are where I call area both times I actually can't really do anything with the output I only see it down in my terminal so how could I get a value from area that I could re use in my program well I should create in this case a return value Let Me Clear My terminal down below and let me modify area to instead return to me some value and return in this sense means that area once it is finished running will give back to me a value I could use my program I could store it in a variable for instance let's type return here our keyword indicate we're going to return some value and let's now type the value we're going to return in this case length times width now that I've done this in my main function below I can actually store this return value from area in its own variable I could say house is a new variable which is assigned the return value of area so we'll read this more so right to left area will run it'll be past these two arguments 50 and 20 area will then run it will run 50 * 20 and returned me that value which I'll then assign to the value of the variable house here I'll do the same thing down here for yard let me go ahead and actually uh let me actually use these values first now that I have these into variables I could find the total area by simply using the values in these variables I could say total a new variable is assigned the result of house plus yard or the value in these two variables added together that is my total area all then down below print something like this convert total to a string and concatenate it here total square ft I'm going go ahead and run python of area. Pi and now I'll see 3500 Square ft so this return value here allowed me to take some value from my function area and use it later on in my program it passed back to me a value that I could then use throughout my main function now a common misconception with these return values well here on line two I'm saying return length time width but you might be inclined to also want to print the the the the current area let's say I wanted to do print um the value of length times width just like this maybe I could both return some value and print the result well actually doesn't quite work like this when I say return online to this means this is the end of my function return indicates not just what value to hand back to whoever called the function but also when my function should end and stop entirely so you see down below here on line three this line is actually kind of more faintly written indicating my program will never get to this line so if I want to do both this act of printing something out having this side effect and returning some value value I'll need to actually move this print statement above my return statement so here I'll print length time width let's go ahead and concatenate that with our square feet as well and then to make things more clear why don't we say total square fet down in Maine and now what I think will happen is this we'll call area the first time with 50 and 20 we'll print out the uh area of my house and then return the value which we'll store in this variable house we'll then call area with 50 and 50 do the same thing now with these two values we'll add the two results together to get total and we'll print one final time the total square feet let's try this out I'll run python of area. piy and I'll see exactly what we wanted to see this then was our short on return values and we'll see you next time