All language subtitles for 6. Introduction & Requirements for the Coffee Machine Project

Now you should have PyCharm up and running,
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and we're finally ready to tackle today's project,
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which we're going to write in PyCharm. You've just been hired.
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Congratulations, but first there's the matter of coffee.
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We all know that programmers can't work unless they're loaded up on coffee.
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So your company has asked you to create the code for a coffee machine.
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Now you, very cleverly, go online and look at the other coffee machines.
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And you notice that it only costs $230 to buy a coffee machine,
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but you're not going to cheat. You're going to create everything from scratch.
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And luckily we don't actually have to build the hardware because we're programmers,
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right?
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But we're going to use this real-life coffee machine as the inspiration for our
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virtual coffee machine, noting the features and the capabilities.
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So what does it say? I found some wonderful graphics on here
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which tells me that they're three hot flavors
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which I'm guessing are these three buttons, it's coins operate
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which I think they mean it's coin operated, and there's not much else that it can
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do.
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Let's take this example and we're going to make a digital version of it.
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We're going to create our own coffee machine.
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And the first step we need to replicate is the ability to make three hot
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flavors. So the flavors we're going to make are 1. espresso,
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2. latte, and 3. cappuccino. Here
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are the recipes for these three types of drinks.
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Each of them requires a different quantity of water,
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a different quantity of coffee and a different quantity of milk.
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And they also each half a different price.
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We're going to be modeling all this data in our coffee machine program as well.
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But luckily for you in the starting code,
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I've already included all of this data inside a dictionary.
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So you don't have to remember this,
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although it might help if you're at home and you decided that you really wanted
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a latte instead of your usual black coffee. Now, in addition,
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the coffee machine has some resources that it has to manage.
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So it starts out with 300ml of water in the tank,
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200ml of milk and 100 grams of coffee.
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The second feature of our coffee machine is that it's coin operated.
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So we're going to be using American coins and they have four types of coins:
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the penny, the nickel, the dime, and the quarter.
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They used to also have the dollar as a coin
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but a few years ago they stopped minting that. So we're not going to count it
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and it probably means one less if statement for us.
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Notice what each of these coins are worth. The penny is worth a cent,
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the nickel worth 5 cents and the dime 10 cents,
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and the quarter is a quarter of a dollar.
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These represented in decimal values would look something like this.
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Now here's the important part. Let's think about what our program requirements are
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if we break it down one.
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1. We need our coffee machine to be able to print a report.
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It needs to be able to tell us what resources it has left,
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how much water has left, how much milk, et cetera.
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If you head over to the completed version of the coffee machine,
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the link is in the course resources,
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and you can go ahead and try out the final version of the coffee machine.
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So let's say that we wanted a report on all the resources that the machine has.
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All we have to do is type report, and we can see all the resources we have.
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Now, in addition to being able to print a report,
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we also want to be able to check that the resources are sufficient when the user
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orders a drink. Now let's say that the user decided to order a latte.
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It asks me to insert some coins and then it gives me the change and it gives me
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the latte. But now if I check the report,
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I can see that I've only got a hundred mils of water left.
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And I know from the previous slide that a latte and a cappuccino is going to
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need more than that amount of water. So let's see what happens
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if I go ahead and order a cappuccino. It says, sorry,
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there's not enough water.
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So our program is able to look through all the resources that the machine has,
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checks it against the recipe of the drink that we're trying to make, and tells the
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user if there is insufficient water or if there's insufficient milk,
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and as long as one of the resources is insufficient,
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then it can't make the drink and it gives the feedback to the user. Now,
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as you saw before,
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our program also needs to be able to process coins because our machine is coin
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operated.
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So no fancy contactless payments or pay with your Apple watch, none of that.
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We've only got coins. When we order something,
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it should ask us to insert coins.
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And it's going to ask for the quantity of each type of coin.
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So let's say that I insert one of each, then in this case,
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there's actually not enough money to cover my drink and it refunds the money and
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doesn't give me a drink. But on the other hand, if I do insert enough money,
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then it should be able to calculate how much money all of these coins are worth
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and then calculate the amount of change based on the cost of my drink.
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And then it should hand me my drink and tell me to enjoy. So,
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in addition to being able to process the four types of coins,
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calculating the actual monetary value based on the number of points,
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it should also check that the transaction is successful.
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That the user didn't try to hoodwink us by not giving enough coins and asking
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for a drink. So if they haven't inserted enough coins,
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then we're just going to refund them and tell them, sorry
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that's not enough money, and not give them their drink.
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But if the transaction was successful,
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then we're going to make the coffee. And in the process of making the coffee,
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we're going to have to deduct the resources.
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Notice how every time we make a drink,
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say in this time we made a latte and previous to the latte,
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we have 300 mills of milk. But after the latte,
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when we asked for the report, you can see that the water has been reduced,
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the milk has been reduced,
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the coffee has been reduced and the money has been put into the coffer.
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This program, even though it seems simple,
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just a simple digital version of a coffee machine,
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it actually has quite a few requirements.
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So I recommend that you look at the screen and try to see how each of the
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requirements work by having a play around with the final version of the code. Now
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I've created a detailed program specification for you as a PDF file
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which you can download in the course resources.
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And this goes into a lot more details on each of those points. For example,
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what should the prompt print in the beginning of the program,
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and then how to turn the machine off,
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how to print the reports and how each of those points should work in detail.
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Go ahead and download this and make sure you read each of the sections and test
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it out in the final working version of the project.
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Once you're ready,
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you can go ahead and head over to the starting version of the code. And again,
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I'm sharing this using Repl.it,
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but I want you to copy everything that's in here,
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there's only one file the main.py file,
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and I want you to create a new project using PyCharm and call it coffee
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machine,
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Right?
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And then create a new file inside your project called main.py,
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and then paste all of the starting code into your main.py.
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And now you are going to code inside this file. And once you're ready,
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you're going to click run and you'll be able to run this main.py down here
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and this will act as your console. Now,
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one really handy feature of
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PyCharm is something called to-do tracking.
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Whereas previously in Repl.it I've been creating to-dos and you've been able to
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view them. But if I have lots of to-dos in different places,
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you can't actually see all of them at once.
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You have to scroll through the file looking for them.
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But in a professional tool,
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we actually have something called to-do tracking and its a tab that's down here.
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So if I go ahead and take some of these program requirements,
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I can put them in as to-dos. To create a
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to-do you have to follow the syntax. First is a pound sign
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and then we write TODO in all caps, and notice how that's just changed color just
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now, and now you can see in the todo tab,
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it's found one todo item.
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Now we can write todo number one
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and this is to print a report of all the coffee machine resources.
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Now let's say that I created a todo somewhere else, right?
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Like all the way up here,
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check that the resources are sufficient to make the drink order. And notice how
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they're completely in different places in a different order.
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But every time I create one of these todos using this format,
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it will get picked up in the
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todo tab. And you can go ahead and see where they live.
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So it's found two items inside our main.py
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and you can see that this one is todo one, this one is todo two.
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And when you click on them,
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they'll take you to the correct places in your code.
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Use this to break down the problem into smaller problems that you can solve one
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by one,
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just as you've done before and try to see if you can complete this project.
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Just the word of warning: this project is quite ambitious.
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But you've now got professional tools to help you,
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and you've got a lot more skill under your belt.
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So give this problem at least an hour to work on it and make sure that you
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satisfy all the criteria that's set out in the program requirements
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and also that your program works exactly the same as the final version of the
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coffee machine.