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All right, guys, so now that we've loaded up all the knowledge that we need into our brains, it's

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time to tackle the final project of the day.

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And as I showed you in the beginning of the day, it's a Rock Paper Scissors game that we can play

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with the computer.

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So the game starts out by asking you to type 0 for rock, 1 for paper, or 2 for scissors.

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So let's go ahead and type two for scissors, and then it's going to show you a graphic of your choice scissors,

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and then the choice the computer made, which is rock. And of course, rock beats scissors

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so you lose.

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What this game boils down to is some way of randomly making a choice between rock, paper, or scissors

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and then comparing that choice that the computer randomly generated against your choice.

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And then based on the rules of rock, paper, and scissors, determining whether if you won, you lost or

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whether if you had a draw.

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While I was looking around, I actually came across the world rock paper scissors association.

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And they have the official rules of the state of Rock Paper Scissors.

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If you're not familiar with this game, it might be worth checking out this website.

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Here are the three shapes of rock, paper, scissors.

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And then the rules are that rock wins against scissors, scissors wins against paper, and paper wins

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against rock.

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Having all of this in mind, head over to replit/@appbrewery/ rock-paper-scissors-start

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and go ahead and just fork the starting project.

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Now you'll notice that in the starting project, I've already got the ASCII art for rock, paper and scissors

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in here and they're each saved to a variable.

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So what that means is that you can start out by just having a go at printing out let's say a rock.

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And remember that these are variable names.

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They're not strings, so they don't need the double quotes around them.

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So let's run that.

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And you can see what we get printed is the particular ASCII art that I chose in my print statement.

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So this is already yours.

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But as you'll notice, there's no other logic that I've provided you and you are going to rely on what

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you learned in the previous days and most importantly, what you've learned in today's lessons to be

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able to complete this challenge.

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And it's worth comparing the outcome against the game of Rock Paper Scissors that I'll link to.

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There's a couple of things to think about, namely, how are you going to decide who won or who lost?

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How are you going to get the computer to choose a random shape, rock, paper, scissors, and how you

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actually get this game to work in the same way that is demoed in this final version?

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I'm going to go quiet now and I'm going to let you pause the video.

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And I want you to spend at least ten or fifteen minutes working on this.

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And if you get stuck, just try some things out or maybe watch some of the previous videos in the day

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and just try to give it your best

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go, and do a lot of struggling.

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Hopefully you're going to succeed.

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And once you're done, head back over here and I'll go through the solution with you.

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So pause the video now.

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All right, so we know that we've got all of this ASCII art, but for the moment, I'm just going to

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start off by putting down the basic logic of this game.

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And it's really helpful for you as well if you start thinking about breaking down the larger problem,

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which is making the Rock Paper Scissors game into smaller problems that you can solve, like generating

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a random number between one and three.

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So we have some sort of proxy for Rock Paper Scissors. And then maybe thinking about putting down

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the logic, well, if the computer chose scissors and I chose paper, then I'm going to lose.

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Or if the computer chose rock and I chose paper, then I'm going to win.

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And putting that down on a flowchart using draw.io or something like that can make this challenge a lot

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easier as well.

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But without further ado, the first thing I need to do is to produce a user choice.

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Now, this is going to be the one that the user chose when they typed in a value.

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And in order to get the value from them, I'm going to need to use a input.

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And inside the input, I'm going to put the following prompt asking the user, what do you choose?

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Type 0 for rock, 1 for paper or 2 for scissors.

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Now, once I get hold of this input, hopefully, if the user is following my instructions, they're going

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to type some sort of number, either zero or one or two.

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Now that I've gotten hold of what the user wants to choose, the next thing to do is figure out what

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the computer is going to choose.

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So I'm going to make another variable called computer_choice and I'm going to generate a random number.

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So to do that, remember, we have to import the random module.

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And then we can start using it to generate random whole numbers by using random.randint.

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And then the range is going to be between zero and two, because this is what I asked the user to do.

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Type 0 for rock, 1 for paper, 2 for scissors.

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So the computer is also going to choose between 0, 1 or 2.

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Now that I've got the computer_choice, I'm actually going to just print it out for now instead of printing

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out the actual shape, I'm just going to print out the number.

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So computer chose and then let's go ahead and add a fstring.

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And of course, that requires the F in front of the string.

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So now if we just play the game as it is, remember that testing up while you're developing it is really,

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really good practice.

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It picks up on the bugs that you make along the way instead of waiting until the end when you've done

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everything

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and then it doesn't work and you have to untangle all of the lines of code.

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At this point, I've already realized that it's actually not so great getting the user to type on this

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line.

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What I would much rather is to start a new line for them to type their answer on.

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So if I run the code again, then it should look a bit like this.

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My prompt is now here. So I'm going to choose 0 for Rock.

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And then it tells me that computer also chose zero.

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So in this case, this would be a draw.

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But if I played this game again, you can see that the computer is probably going to choose something

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different.

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So I chose rock again

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the computer chose 1, which is paper.

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So now we can start thinking about how do we compare these two choices and how can we define the logic

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of Rock Paper Scissors?

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So I know that paper beats rock, scissors beats paper and rock will beat scissors.

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So if zero is rock, one is paper and two is scissors, then two beats one and one beats zero.

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So that's very simple for us to check in terms of using if statements,

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right?

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We could simply just check

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well, if the computer choice is greater than the user choice, well then this probably means that the

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computer wins.

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But this is not true in all cases, right? Because if the computer chose 2 for scissors and the user

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chose 0 for rock, then the user should win rather than the computer winning.

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So we actually have some exceptions to this rule.

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How can we catch the exceptions before we go down to this level of generalization?

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Well, we could instead of using this as an if, we use this as an elif and we create another if statement

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which says, well, if the user_choice is equal to zero, so if the user chose rock and the computer_choice

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was 2, well then this means that in this case, the user actually wins.

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Now, if we're thinking from the perspective of the user when they're playing this game, then they

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don't really care if the computer won or the user won. They want to know, did they win or did they lose?

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So let's change this wording a little bit.

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We'll say, instead of user wins, we'll say you win.

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And if the computer wins, then we'll say you lose.

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So now if we run our program and test it out, so let's say I'm going to type 0 for rock and the

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computer chooses 2, but we actually get an error.

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It tells us that the greater than comparison is not supported between instances of int and string.

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What's going on here?

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Well, remember that we get our inputs as a number, but the input is always going to be a string.

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So if we want this to be a number,

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then we're going to have to wrap it inside an int.

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So now we turn it into a whole number.

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Now, this might be a good point to address

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well, what should happen if they typed something that wasn't 0, 1 or 2, whether they typed 34?

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Well, then naturally they should probably lose,

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right?

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So we can add an else statement addressing this situation. So we could say else we just print

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You typed an invalid number.

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You lose. Cool.

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So that sorts that out.

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Now let's run our code again and see if it works.

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What do you choose?

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Type 0 for Rock.

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I'm going to choose rock again.

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Computer chose zero and it tells me that you typed an invalid number.

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Well, actually, zero is not an invalid number.

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So what's going on here?

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Well, it's because it didn't fit this criteria.

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So I had zero,

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computer had zero, and it didn't fit this criterion because zero is not greater than zero.

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So it basically defaulted to the final else statement.

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But what's actually happening here is that that was a draw.

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Computer chose rock,

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I chose rock.

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That's a draw in the official rules of Rock Paper Scissors.

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So how do I catch that?

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Well, I could create another elif statement which says, well, if the computer_choice is equal to

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the user_choice, well, then we're going to print

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it's a draw.

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Now, let's test our app again and see if there are any other situations where our code is not behaving

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properly.

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I'm going to choose rock again, computer chose rock as well.

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And I guess it's a draw, so that's pretty good.

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Now, if I choose 0 and the computer chose 2, then this is going to be the statement that gets

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triggered and I win.

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So that's pretty good.

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Now, what if I chose 2 for scissors and the computer chose 0?

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Well, in this case, rock beats scissors

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so it should actually say I lose.

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But instead it says you typed an invalid number.

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So it defaulted to the else statement again because this particular situation is not caught by any of

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these statements.

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So what do we have to do instead?

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Well, we actually need another elif to say, well, if the computer_choice was equal to 0 and

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the user_choice was equal to 2, well, this means that rock beats scissors

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so I lose and the computer wins.

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Now, the final one that we need to catch is this case.

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If I type 1 for paper and computer chooses 0 for rock, it again defaults to the else statements

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whereas in fact in this case it should tell me that I won.

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So what's missing here?

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Well, it's the partner to this particular statement.

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If computer_choice is greater than user_choice then I lose.

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But on the other hand, if the user_choice was greater than the computer_choice, then I actually should

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win.

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So now the final thing we might have to fix is this else statement now actually never gets called because

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this is what happens.

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So let's say that I choose 456.

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It tells me that computer chose 2, I win.

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What's happening here?

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Well, it's actually this particular line that's being carried out.

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user_choice is greater than computer_choice.

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This is not what we want.

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We want it to default to

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You typed an invalid number.

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You lose. So we can actually just use else in this situation.

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We actually need to provide a condition.

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We're going to use elif to check if the user_choice is greater or equal to three,

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now, the computer will never choose anything other than 0, 1 and 2

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so we don't have to check that one.

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But the user could choose something above 3 or below 0.

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So we can use an or statement to catch this. Or if the user_choice is less than zero,

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well, in this case, you typed an invalid number, you lose.

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But that's not all that we have to do.

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If we hit run and we again type some extraordinarily large number, you'll see that it still says

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computer chose 1.

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You win.

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What's going on?

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We have this statement that should catch this situation, but it's right at the bottom.

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So it's not going to be checked until one of the previous ones are checked.

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Namely, it's one of these that's going to be the problem.

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So what we have to do is we have to move this statement above all the lines so that we first check if

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the user_choice is greater than three or less than zero.

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And if that's not true, do we actually continue checking to see who won the game.

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Now, finally, we can run our code type an invalid number and get you typed an invalid number. You lose.

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So now that we've actually got our logic all sorted out, the next step is to include our images.

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And to do that, we have to somehow match it up with these numbers we have,

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right? 0, 1 and 2.

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Now, there's many, many ways that you could do this and you could solve this project.

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But the easiest way is probably putting the game images into a list where we have rock as the first

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one, paper as the second one and scissors as the last one.

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So we're using the fact that lists have a order that is always going to be followed. So we can now get

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hold of the rock picture by getting game_images[0].

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We can get scissors by doing game_images[2] and so on and so forth. And we can match those up to our

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choices, the user_choice and the computer_choice.

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So when the user chooses a number, then we're going to print from the game_images and we're going to

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use our little square brackets to select the image we want from this list.

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And the one that we want is going to be based on the user's choice, right?

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0 for rock, 1 for paper, 2 for scissors.

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So we're going to put user_choice as the index to pick out an image from game_images. Now down here for

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the computer_choice, instead of printing the number that the computer chose, I'm going to delete that

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and add a little colon.

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So that way it's going to show computer chose

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and then I'm going to print the image of the choice that the computer made.

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So I'm going to add another print statement,

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I'm going to tap into the game_images and then inside some square brackets, I'm going to use the computer

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choice which is going to be between 0, 1 and 2 as the index to pick out the corresponding image

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from my list game_images.

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So now we're finally ready to run our code and I'm going to choose 0 for rock and the computer chose

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paper.

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So paper beats rock, I lose.

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Let's try this again.

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I'm going to choose scissors and computer chose scissors.

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It's a draw. But we have also introduced a bug.

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So if we test this using a number that's outside of this range, 0, 1 or 2,

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so let's try 5. And we hit enter,

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what do we get?

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We get a index error.

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So what has happened here?

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Well, this is up to you to debug.

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Well, this is a really good opportunity for you to practice your debugging.

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So think about what has

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changed since the last time we tested this and how you can fix the code so that it works as expected,

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so telling us that you typed an invalid number, you lose whenever we type a number that's above or

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equal to three or less than zero.

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So I want you to pause the video and see if you can debug this challenge so that when you type in 5,

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you get this printed. Pause video now.

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All right, so what's going on here, because we tested this and it worked, but in between that time,

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we also added this line because we wanted to get a hold of the game images based on the user's choice.

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Now, at this point, the user's choice is unchecked by the if statement.

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So it could still be equal to 4 or 5 or 10 or a million.

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So if in that case, it tries to get hold of the fifth image from the game_images list, well, it doesn't

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exist.

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There's only 0, 1 and 2.

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So to fix this, we need to move this if statement so that it gets checked before this line of code

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gets carried out.

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So let's go ahead and cut this line of code out and put it right above this print statement.

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So in this case, if the user types in a choice that's above or equal to three or less than zero,

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we're going to print this.

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But else, if they typed in any other number, then we want the rest of the code to continue.

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So let's select the rest of the code, hit tab and tab it over

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so that is included under the else statement.

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Now let's go ahead and change this from elif just to an if because we're no longer checking it as another

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else-

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if statement. It is just a straight up

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if. So, in this case, if they typed a 5, then it will go into this basket and it will finish there.

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But otherwise, it will go into this basket and it will continue checking later on.

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So did you manage to debug your code and figure out the issue?

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This is one of the most important skills

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as a programmer. You have plenty of opportunities coming up to practice your debugging.

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And if you ever want more practice, head over into the Q&A and see what other students have issues

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with and see if you can help them out by practicing your debugging skills.

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Now, we have completed the project by using everything from lists to randomization to variables to

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if statements and a whole lot of logic.

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So how did you get on with this project? If you struggle

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this is the time again to go back to it and maybe map things out using a flow diagram or try to run

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the code using Thonny to see how it does it step by step.

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But the important thing is that you got to write your own code and you got to make it work.

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And this is the only way that you'll understand what's going on so that you can continue on.

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And as things get harder, you'll be able to learn more because you've already understood all of the

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previous knowledge.

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So I hope you had fun with me today

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learning and building, and hopefully I will see you tomorrow bright and early.

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So that's good night from me for today.