1 00:00:00,150 --> 00:00:00,540 Now, 2 00:00:00,540 --> 00:00:05,540 there are so many possible solutions to create this coffee machine program 3 00:00:05,760 --> 00:00:10,760 satisfying all the requirements. And the way that you code it up is essentially 4 00:00:12,000 --> 00:00:13,080 your choice, right? 5 00:00:13,440 --> 00:00:17,970 Whether if you decide to use a while loop or use a for loop or create a 6 00:00:17,970 --> 00:00:21,540 different data structure, there are endless possibilities. 7 00:00:21,840 --> 00:00:25,320 What I'm going to show you now is just one of those possibilities. 8 00:00:25,890 --> 00:00:29,790 And what's really important is you don't feel like you've done it wrong 9 00:00:29,790 --> 00:00:33,120 just because it's different to mine. As long as it works 10 00:00:33,120 --> 00:00:36,900 the way that you expect it to, then consider yourself successful. 11 00:00:37,650 --> 00:00:41,520 The first thing I'm going to do is create a new project in PyCharm, 12 00:00:41,910 --> 00:00:46,740 and I'm going to call my project coffee machine. Again, 13 00:00:46,770 --> 00:00:51,570 making sure that I've got the latest version of Python as the interpreter I'll 14 00:00:51,570 --> 00:00:52,403 click 15 00:00:52,490 --> 00:00:53,323 create. 16 00:00:54,860 --> 00:00:58,700 Now that the first thing I'm going to do here is right-click on this and create 17 00:00:58,730 --> 00:01:02,210 a new file, which is going to be my main.py. 18 00:01:02,810 --> 00:01:07,160 And then I'm going to go to my starting project in Repl.it and I'm just going to 19 00:01:07,160 --> 00:01:12,160 copy everything there is over here and paste it into this main.py. 20 00:01:13,370 --> 00:01:18,370 Now you might find the font of your code or of PyCharm a little bit too big or 21 00:01:19,190 --> 00:01:21,350 too small. If that's the case, 22 00:01:21,350 --> 00:01:26,350 you can just go into preferences and change the appearance and the font to a 23 00:01:27,830 --> 00:01:30,680 different size. And this is for the user interface. 24 00:01:31,130 --> 00:01:35,210 And if you want to change the font of the editor, then you can go here, 25 00:01:35,270 --> 00:01:38,120 go to font and then change that size here. 26 00:01:38,600 --> 00:01:41,810 I've tried to make it as large as possible so that when you were looking at this 27 00:01:41,810 --> 00:01:46,100 video on an iPad or an iPhone, all the code still be readable. 28 00:01:46,460 --> 00:01:48,230 But of course, normally when you're coding, 29 00:01:48,230 --> 00:01:52,250 you'd probably want to fit more lines into the same screen, 30 00:01:52,730 --> 00:01:56,300 but it's not good to strain your eyes. So try to strike a balance there. 31 00:01:57,110 --> 00:02:00,800 Now I'm going to collapse that sidebar because I'm going to be coding entirely 32 00:02:00,800 --> 00:02:01,880 in this one file. 33 00:02:02,510 --> 00:02:06,080 Now notice that the beginning we get given a menu, 34 00:02:07,070 --> 00:02:11,210 and this is a dictionary which contains three entries. 35 00:02:11,690 --> 00:02:15,050 And each of those entries have a name of a drink, 36 00:02:15,140 --> 00:02:16,820 espresso, latte and cappuccino. 37 00:02:17,210 --> 00:02:21,140 And then each of them have a value that holds a bunch of data, 38 00:02:21,500 --> 00:02:24,650 including the ingredients that are required to make that drink 39 00:02:24,980 --> 00:02:29,840 and also the price of the drink. Now there's also a resources dictionary, 40 00:02:29,870 --> 00:02:32,900 which holds the resources of the coffee machine. 41 00:02:33,740 --> 00:02:36,440 Now that we've got all of that, then we're ready to go. 42 00:02:37,070 --> 00:02:39,740 I'm going to tackle these requirements one by one. 43 00:02:40,370 --> 00:02:43,670 And the first one says to prompt the user by asking, 44 00:02:43,700 --> 00:02:46,880 what would you like? Espresso, latte or cappuccino. 45 00:02:46,880 --> 00:02:51,880 So I'm actually gonna just straight up copy this line and put that into an 46 00:02:51,950 --> 00:02:55,730 input. This is going to be saved into some sort of variable, 47 00:02:55,730 --> 00:02:57,140 which I'll name choice. 48 00:02:58,550 --> 00:03:03,010 Now it tells me that the prompt should show every time action has completed. 49 00:03:03,280 --> 00:03:03,820 For example, 50 00:03:03,820 --> 00:03:07,660 once the drink is dispensed and it should show again and again and again. 51 00:03:07,930 --> 00:03:11,970 So that means we probably going to have to embed this input in some sort of while 52 00:03:11,970 --> 00:03:16,270 loop. So I'm just gonna say for now while something is true, 53 00:03:16,570 --> 00:03:20,110 then keep asking for this prompt. Right now 54 00:03:20,140 --> 00:03:25,140 if we decide to go and run this code where we go to run and then click on this 55 00:03:25,540 --> 00:03:29,140 button and then select the main.py to run, 56 00:03:29,800 --> 00:03:33,790 then you can see that it asks me what would you like? And if I've put an input, 57 00:03:33,880 --> 00:03:36,910 it'll keep asking me until eternity, basically, 58 00:03:36,910 --> 00:03:40,870 because that there's currently no way of turning that true into a false. 59 00:03:41,740 --> 00:03:43,720 So let's take a look at the next requirement. 60 00:03:43,900 --> 00:03:48,010 We should be able to turn off the coffee machine by entering off into the prompt. 61 00:03:48,610 --> 00:03:50,290 For maintainers of the coffee machine, 62 00:03:50,290 --> 00:03:54,160 they can use off as the secret word to turn off the machine and your code should 63 00:03:54,160 --> 00:03:58,450 end execution when this happens. So when somebody wants to buy coffee, 64 00:03:58,480 --> 00:04:03,160 this is the line that they see. But when a maintenance guy comes along, 65 00:04:03,160 --> 00:04:05,140 then they should be able to enter something. 66 00:04:05,500 --> 00:04:08,290 And if this choice happens to equal the secret code, 67 00:04:08,590 --> 00:04:13,090 which is off, then in this case we should stop the while loop and exit. 68 00:04:13,510 --> 00:04:18,510 So that gives us a way of changing this true into some other form of variable, 69 00:04:18,870 --> 00:04:22,320 right? So we could create a new variable code is_on, 70 00:04:22,650 --> 00:04:27,180 start it off as true and while the machine is on, 71 00:04:27,510 --> 00:04:31,530 then it should continue to loop through and ask the user for their choice. 72 00:04:31,890 --> 00:04:35,280 But if the choice happens to be off, then we're going to turn 73 00:04:35,280 --> 00:04:39,060 that is_on into false. Now, 74 00:04:39,060 --> 00:04:40,650 if we run our code again, 75 00:04:40,650 --> 00:04:44,790 so now that you've run it once you can either stop it or you can rerun it, 76 00:04:45,390 --> 00:04:49,770 and now it's going to stop your existing code and rerun the code. 77 00:04:50,040 --> 00:04:52,140 So if you don't want to see this dialogue every time, 78 00:04:52,170 --> 00:04:55,230 then just check this box and then click stop and rerun. 79 00:04:55,950 --> 00:05:00,950 So now if we make a selection or we say something basically anything other than 80 00:05:01,380 --> 00:05:02,970 the key word, which is off, 81 00:05:03,240 --> 00:05:06,810 it's going to loop back and forth and keep prompting us. 82 00:05:07,170 --> 00:05:12,170 But if I say off, then the machine turns off and you can see that I've now exited 83 00:05:12,870 --> 00:05:16,920 the program. Now we've tackled 1 and 2. 84 00:05:16,950 --> 00:05:21,930 Let's go on to number 3. When the user enters the keyword report to 85 00:05:21,930 --> 00:05:24,600 the prompt, another secret word, a report 86 00:05:24,630 --> 00:05:28,410 should be generated that shows the current resource values. For example, 87 00:05:28,410 --> 00:05:33,150 water, milk, coffee, and money. So how can we do that? Well, firstly, 88 00:05:33,180 --> 00:05:36,360 we don't actually have a variable that holds the amount of money. 89 00:05:36,690 --> 00:05:37,950 So let's create something, 90 00:05:37,950 --> 00:05:41,940 let's call it profit maybe and set it to equal zero to begin with. 91 00:05:42,240 --> 00:05:44,790 Our machine has an empty money box in the beginning. 92 00:05:45,390 --> 00:05:48,720 So now we have to check to see, well, elif 93 00:05:48,750 --> 00:05:52,590 the choice was equal to report. Well, in this case, 94 00:05:52,620 --> 00:05:57,620 we have to generate a report and the report is basically going to print all the 95 00:05:58,820 --> 00:06:00,500 values of these resources. 96 00:06:01,010 --> 00:06:06,010 So I'm simply going to copy the expected output and I'm going to paste it here. 97 00:06:07,550 --> 00:06:12,080 And then we can try and turn that into print statements, 98 00:06:12,170 --> 00:06:16,220 making it a dynamic instead of hard-coded. In my case, 99 00:06:16,220 --> 00:06:19,670 I want to add print in front of all of these lines. 100 00:06:19,790 --> 00:06:23,990 And previously we've been doing this just by writing it one by one, 101 00:06:23,990 --> 00:06:25,970 and then maybe we could copy and paste it. 102 00:06:26,330 --> 00:06:30,890 But let me show you a quick tip that you can do in PyCharm. If you're on Windows, 103 00:06:30,920 --> 00:06:35,510 hold down the alt and the shift key on your keyboard. If you are on a Mac, 104 00:06:35,540 --> 00:06:37,790 hold down the option and the shift key. 105 00:06:38,300 --> 00:06:42,710 Now click at the beginning and hold and drag down. 106 00:06:43,580 --> 00:06:45,470 So if that doesn't work, try out a few times, 107 00:06:45,470 --> 00:06:49,400 you'll get the hang of it eventually. But notice how I've now got four cursors 108 00:06:49,520 --> 00:06:52,580 and that means when I write print, check this out. 109 00:06:53,870 --> 00:06:54,703 Isn't that cool? 110 00:06:55,550 --> 00:06:59,780 I've managed to write on four lines at once because I need that repeat 111 00:06:59,780 --> 00:07:03,980 functionality and this is a way of doing multiline editing. 112 00:07:04,190 --> 00:07:07,910 Remember that shortcut and use it in the future if you find it useful. 113 00:07:08,480 --> 00:07:13,430 So I'm actually going to change this all into fstrings because I want to change 114 00:07:13,460 --> 00:07:16,160 these numbers instead of being hard-coded, 115 00:07:16,490 --> 00:07:19,700 I want to insert them into here using the curly braces. 116 00:07:20,210 --> 00:07:23,120 The water is stored under resources, 117 00:07:23,510 --> 00:07:26,270 and then it's in the key called water. 118 00:07:27,830 --> 00:07:31,670 And now notice how I've got a outer double quote, 119 00:07:31,910 --> 00:07:33,770 so I can't have an inner double quote. 120 00:07:33,770 --> 00:07:37,100 So I'm going to change this into single quotes instead, 121 00:07:38,960 --> 00:07:42,530 like, so. And I'm going to do the same for milk and coffee. 122 00:07:44,420 --> 00:07:48,590 So now I've added the water, milk, and coffee into my print statement. 123 00:07:48,620 --> 00:07:50,990 All I have left is the money. 124 00:07:51,230 --> 00:07:56,230 So let's delete the value and let's insert that profit into here. 125 00:07:57,020 --> 00:08:00,170 Now let's run our code again and let's check it out. 126 00:08:00,650 --> 00:08:05,650 If I type report it should now give me a report of all the current values and 127 00:08:06,140 --> 00:08:10,130 money is equal to $0 because that's what we start off with. 128 00:08:11,120 --> 00:08:14,540 We're now ready to tackle number 4. Here 129 00:08:14,570 --> 00:08:19,370 we have to check that when the user chooses a drink, we're going to check 130 00:08:19,370 --> 00:08:23,360 if there are enough resources to make that particular drink they chose. 131 00:08:23,690 --> 00:08:26,630 For example, if a latte requires 200 ml of water 132 00:08:26,930 --> 00:08:29,390 but there's only 100ml left in the machine, 133 00:08:29,750 --> 00:08:32,960 it should not make the drink because it actually can't make the drink 134 00:08:33,289 --> 00:08:37,390 and it's going to print out, 'Sorry, there's not enough water' or not enough milk, 135 00:08:37,440 --> 00:08:39,320 not enough coffee, whatever it may be. 136 00:08:39,770 --> 00:08:42,350 So let's tackle this particular checkpoint. 137 00:08:43,909 --> 00:08:48,650 Now that I've got the if choices equal off, if choice equals report. 138 00:08:48,980 --> 00:08:50,990 Now, if it's not either of those, 139 00:08:51,020 --> 00:08:54,080 then they're probably going to be entering the name of a drink. 140 00:08:54,380 --> 00:08:56,820 So let's catch that using an else statement. 141 00:08:57,480 --> 00:08:59,430 And then inside this else statement 142 00:08:59,430 --> 00:09:04,350 I'm going to get hold of the particular drink that they ordered by tapping into 143 00:09:04,350 --> 00:09:09,120 our menu dictionary and then using that choice they typed in as the key. 144 00:09:09,630 --> 00:09:14,190 Let's say that the particular drink that they chose is equal to menu 145 00:09:14,610 --> 00:09:18,480 and then the key is of course going to be the choice. 146 00:09:18,930 --> 00:09:23,930 So now if I just print this drink and I run my code.. 147 00:09:24,270 --> 00:09:29,270 So the shortcut for running is actually holding down the control and R and now 148 00:09:29,730 --> 00:09:34,200 it can go down here and you can see it's asking me for what I would like, 149 00:09:34,230 --> 00:09:38,010 so I'm going to choose latte. And what's going to be printed 150 00:09:38,040 --> 00:09:43,040 is the latte entry in my recipes dictionary up here, so this particular 151 00:09:44,010 --> 00:09:44,843 value. 152 00:09:46,050 --> 00:09:50,070 Now that I've got this value stored inside a variable called drink, 153 00:09:50,340 --> 00:09:55,340 well then I can tap into its ingredients and loop through each of the ingredients 154 00:09:56,160 --> 00:10:00,600 comparing it against the resources and seeing if there's enough. 155 00:10:00,990 --> 00:10:04,680 Now this is a little bit of functionality that should probably be self- 156 00:10:04,680 --> 00:10:07,950 contained. So instead of just printing the drink, 157 00:10:07,950 --> 00:10:11,520 I'm actually going to create a new function. So up here, 158 00:10:11,520 --> 00:10:15,930 I'm going to create a new function with our def and I'm going to call it is_ 159 00:10:15,960 --> 00:10:17,940 resource_sufficient. 160 00:10:20,370 --> 00:10:25,370 And this is_resource_efficient is going to take the order ingredients as a 161 00:10:27,180 --> 00:10:29,910 input and then it's going to work on that. 162 00:10:29,910 --> 00:10:34,860 So if we want to call that function and pass in the order ingredients we'll have 163 00:10:34,860 --> 00:10:36,930 to call is_resource_efficient 164 00:10:37,410 --> 00:10:42,410 and then the other ingredients will be from the drink and then getting hold of 165 00:10:43,350 --> 00:10:46,470 the values under the key ingredients. 166 00:10:48,860 --> 00:10:49,580 All right. 167 00:10:49,580 --> 00:10:54,350 So under this particular key, it will fetch this particular dictionary. 168 00:10:54,710 --> 00:10:58,880 And this is the dictionary that's going to be passed over to this function as 169 00:10:58,880 --> 00:10:59,713 the input. 170 00:11:00,140 --> 00:11:04,130 So now that we have a hold of a dictionary with all the ingredients that are 171 00:11:04,130 --> 00:11:06,950 required and the amount of each ingredient, 172 00:11:07,250 --> 00:11:09,950 we can now compare it against our resources 173 00:11:09,980 --> 00:11:14,980 which is a very similar dictionary with the resources and the amount that's left 174 00:11:15,800 --> 00:11:16,633 in the machine. 175 00:11:17,750 --> 00:11:22,750 We can loop through the order ingredients and for each of the items in the 176 00:11:23,720 --> 00:11:24,380 ingredients, 177 00:11:24,380 --> 00:11:29,380 we're going to check to see if the order ingredients at that particular key, 178 00:11:30,080 --> 00:11:35,080 so this is getting hold of the value, is greater than or equal to the resources 179 00:11:37,700 --> 00:11:41,090 using the same particular key. For example, 180 00:11:41,090 --> 00:11:43,580 if we were looking at the first example, 181 00:11:43,940 --> 00:11:46,580 the item would be equal to water. 182 00:11:47,090 --> 00:11:51,020 So if we fetch the value from order ingredients 183 00:11:51,050 --> 00:11:54,010 with the key of water, we should get of 200. 184 00:11:54,460 --> 00:11:59,460 And we would now test to see if 200 is greater than or equal to the 300 that 185 00:12:02,110 --> 00:12:05,050 we have under the resources. Well, in this case, 186 00:12:05,080 --> 00:12:09,370 then we should probably tell the user that we actually can't make it. 187 00:12:09,370 --> 00:12:14,370 So let's put an if statement there and I'm going to use this same string here to 188 00:12:15,880 --> 00:12:16,713 print it out. 189 00:12:18,340 --> 00:12:22,000 Now notice when I pasted that string in and 190 00:12:22,000 --> 00:12:27,000 it has the double quotes from the PDF file here that it's actually not being 191 00:12:27,910 --> 00:12:29,740 recognized and I'm getting an error here. 192 00:12:30,220 --> 00:12:33,820 And the important thing to know is that there's a difference between decorative 193 00:12:33,820 --> 00:12:35,260 double quotes, like these, 194 00:12:35,320 --> 00:12:38,680 which looked different for the beginning quote and the end quote. 195 00:12:39,130 --> 00:12:43,060 And then there are Programming double quotes which look like this, 196 00:12:43,060 --> 00:12:44,770 so I'm going to select this whole line 197 00:12:45,070 --> 00:12:50,070 and I'm going to add a double quote and notice how they look identical from the 198 00:12:50,260 --> 00:12:54,550 front and the back. So now it's going to print, Sorry 199 00:12:54,550 --> 00:12:56,050 there is not enough. 200 00:12:56,140 --> 00:12:59,560 And the enough of what? It's going to be 201 00:12:59,590 --> 00:13:01,990 the item that we're currently looping through. 202 00:13:02,500 --> 00:13:04,210 So let's change that to an fstring 203 00:13:04,540 --> 00:13:08,080 which makes that an active piece of code that's going to be inserted. 204 00:13:08,980 --> 00:13:09,880 And in this case, 205 00:13:09,910 --> 00:13:14,530 we're going to return false because there is not enough resources. 206 00:13:14,980 --> 00:13:16,210 But otherwise, 207 00:13:16,450 --> 00:13:21,130 if we managed to get to the end of the for loop and we still haven't returned or 208 00:13:21,130 --> 00:13:25,420 exited the function by returning false, then in this case 209 00:13:25,450 --> 00:13:26,560 we can return true. 210 00:13:26,980 --> 00:13:30,520 So if this particular logic is a little bit confusing for you, 211 00:13:30,520 --> 00:13:35,080 you could have something like, like this. 212 00:13:35,110 --> 00:13:39,730 So you have is_enough = true, and you could change is_enough 213 00:13:41,380 --> 00:13:42,640 to false. 214 00:13:42,910 --> 00:13:46,810 If any of the order ingredients are greater than the resources. 215 00:13:47,380 --> 00:13:51,250 And finally at the end, you could return is_enough. 216 00:13:51,460 --> 00:13:55,630 So basically it stays true unless one of these if statements gets activated. 217 00:13:56,800 --> 00:14:01,540 But for simplicity sake, I'm actually just going to keep it simple like this. 218 00:14:02,140 --> 00:14:04,720 And we're now ready to receive that result here 219 00:14:05,140 --> 00:14:07,270 so we can put an if statement here. 220 00:14:07,390 --> 00:14:10,630 If the resources are sufficient for the drink, 221 00:14:11,080 --> 00:14:14,800 then we can proceed to continue to the next step. 222 00:14:15,970 --> 00:14:18,580 The next step is to process coins. 223 00:14:18,730 --> 00:14:21,820 The user's going to be asked for the number of quarters 224 00:14:21,820 --> 00:14:24,070 they have, the number of dimes, nickels, and pennies, 225 00:14:24,460 --> 00:14:26,950 and you have to remember their values. 226 00:14:26,980 --> 00:14:31,000 So if you're from the US this shouldn't be a problem. But if you're like me 227 00:14:31,030 --> 00:14:33,610 somebody who's not from the US, um, 228 00:14:33,640 --> 00:14:36,940 I actually find it really confusing when I go to the States. 229 00:14:37,450 --> 00:14:41,860 I always think that the larger coin, that the nickel, should be worth more than 230 00:14:41,860 --> 00:14:44,200 the dime, but I think it was just me being silly. 231 00:14:45,070 --> 00:14:49,570 So we're going to ask the user to insert some coins, we're going to process it 232 00:14:49,630 --> 00:14:52,340 and then we're going to calculate the total value of the coins 233 00:14:52,340 --> 00:14:54,590 they inserted. That, to me, 234 00:14:54,590 --> 00:14:57,440 sounds like it should be a separate function as well. 235 00:14:58,040 --> 00:15:02,120 So let's create another function here, which I'm going to call process_coins. 236 00:15:04,130 --> 00:15:06,410 And this is not going to take any input, 237 00:15:06,470 --> 00:15:10,610 but it is going to return the total value of the coins inserted. 238 00:15:11,270 --> 00:15:13,310 Now, how do we process coins? Well, 239 00:15:13,310 --> 00:15:18,310 first we can print to ask them to please insert coins. 240 00:15:19,340 --> 00:15:23,780 And then afterwards, we're going to somehow calculate a total, right? 241 00:15:23,810 --> 00:15:25,940 This is the variable that we're going to keep track of 242 00:15:26,270 --> 00:15:29,150 and we're going to return as the output of this function. 243 00:15:29,930 --> 00:15:34,160 The total is going to be calculated based on the four types of coins. 244 00:15:34,670 --> 00:15:38,600 So the first question we're going to ask them is how many quarters? 245 00:15:40,700 --> 00:15:43,670 And this of course is going to be a whole number, 246 00:15:43,670 --> 00:15:46,910 so we're going to turn it from a string into an integer. 247 00:15:47,570 --> 00:15:51,860 And we know that each quarter is worth 0.25 248 00:15:51,860 --> 00:15:53,090 of a dollar, 249 00:15:53,390 --> 00:15:57,470 so we can multiply the number of quarters by 0.25 250 00:15:57,770 --> 00:15:59,720 and then we'll get the monetary value. 251 00:16:01,190 --> 00:16:06,190 Now we'll need to do the same thing for a bunch of other coins. 252 00:16:06,980 --> 00:16:09,860 So instead of quarters, this is going to be dimes, 253 00:16:10,130 --> 00:16:14,690 and then it's going to be nickels and finally, 254 00:16:14,690 --> 00:16:18,920 it's going to be pennies. Dimes are worth 10 cents, 255 00:16:19,310 --> 00:16:21,380 nickels are worth 5 cents, 256 00:16:22,010 --> 00:16:26,030 and pennies are worth 1 cent. Now, 257 00:16:26,060 --> 00:16:30,950 instead of just setting the totals of each of these values, every subsequent one 258 00:16:30,980 --> 00:16:32,240 other than the first one 259 00:16:32,240 --> 00:16:35,810 which remember creates this variable and sets its value, 260 00:16:36,230 --> 00:16:41,230 every other one is just going to be added to the current value like this. 261 00:16:42,620 --> 00:16:44,840 So now at the very end of all of this, 262 00:16:44,870 --> 00:16:48,260 we're going to return the total as the output. 263 00:16:48,740 --> 00:16:52,850 And whenever you have something that returns like both of these functions, 264 00:16:53,210 --> 00:16:56,960 you should probably be adding a docstring. So in this case, 265 00:16:56,960 --> 00:16:58,280 this returns 266 00:16:58,280 --> 00:17:02,870 the total calculated from coins 267 00:17:02,870 --> 00:17:06,349 inserted. And in this case, 268 00:17:06,380 --> 00:17:11,380 what happens is it returns true when order can be made and false 269 00:17:15,500 --> 00:17:19,130 if ingredients are insufficient. 270 00:17:20,990 --> 00:17:25,160 Now let's call this function that we created, process_coins. 271 00:17:25,849 --> 00:17:28,310 If there's enough resources to make the drink, 272 00:17:28,339 --> 00:17:31,520 then the next step is to actually ask them for the money. 273 00:17:31,820 --> 00:17:34,820 So here is where we're going to call process coins. 274 00:17:35,450 --> 00:17:40,400 And notice when I write this and I hover over it, you can see that docstring 275 00:17:40,400 --> 00:17:43,700 we just wrote, returns the total from coins inserted. 276 00:17:44,990 --> 00:17:47,180 That means this is going to return 277 00:17:47,330 --> 00:17:52,110 and we need to capture the user's payment in this variable. 278 00:17:52,110 --> 00:17:56,760 So this returns the output replaces this function call, 279 00:17:57,060 --> 00:18:01,230 and then it gets saved inside this variable called payment. Now, 280 00:18:01,230 --> 00:18:05,340 what are we going to do with this payment? Well, that goes onto the next step, 281 00:18:05,790 --> 00:18:08,970 which is to check that the transaction was successful. 282 00:18:09,270 --> 00:18:13,380 So we have to make sure that the user has inserted enough money to actually 283 00:18:13,380 --> 00:18:18,060 purchase the drink they wanted. But each drink of course has a different price. 284 00:18:18,330 --> 00:18:22,920 So if the user inserts enough money, then we're going to give them some change. 285 00:18:23,250 --> 00:18:26,910 But if they haven't inserted enough money, then we're going to say, sorry, 286 00:18:26,910 --> 00:18:29,460 that's not enough money. And the money is refunded. 287 00:18:30,240 --> 00:18:33,990 But if they have inserted enough money then the cost of the drink is going to be 288 00:18:33,990 --> 00:18:38,700 added to the machine as the profit. So the next time when we trigger the report, 289 00:18:38,730 --> 00:18:42,570 then we're going to get to see the increase in the monetary value. 290 00:18:44,010 --> 00:18:44,490 Again, 291 00:18:44,490 --> 00:18:48,900 let's create a new function and let's get rid of some of these squiggly lines by 292 00:18:48,900 --> 00:18:51,630 adding enough spaces in between the functions. 293 00:18:52,530 --> 00:18:56,370 This one I'm going to call is_transaction_successful, 294 00:18:58,290 --> 00:19:00,810 because that's basically what we're going to be checking. 295 00:19:01,380 --> 00:19:03,990 And it's going to take two inputs. 296 00:19:04,110 --> 00:19:08,520 It's going to take a input in terms of the amount of money that was received, 297 00:19:09,180 --> 00:19:14,130 and it's also going to have another input, which is cost of the drink. 298 00:19:15,060 --> 00:19:20,060 This function's goal is to return true when the payment is accepted or it's 299 00:19:24,570 --> 00:19:25,980 going to return false 300 00:19:26,370 --> 00:19:29,610 if the money is insufficient. 301 00:19:29,630 --> 00:19:30,463 Uhm 302 00:19:32,390 --> 00:19:36,410 Notice how there's this line to the right here of your editor. 303 00:19:36,890 --> 00:19:41,890 Basically what happens is if you have a line of code that's a little bit too 304 00:19:41,930 --> 00:19:45,320 long past the recommendation from PEP 8, 305 00:19:45,650 --> 00:19:50,150 you can see that PEP 8 recommends that a line should not be longer than 120 306 00:19:50,150 --> 00:19:50,983 characters 307 00:19:51,140 --> 00:19:54,650 because it's very hard to read for somebody scrolling around like this. 308 00:19:54,980 --> 00:19:55,880 So in this case, 309 00:19:55,880 --> 00:20:00,020 they would want you to put it onto a new line so that you don't have to scroll 310 00:20:00,020 --> 00:20:03,500 and you can see it all on the same screen. But in our case, 311 00:20:03,500 --> 00:20:07,520 this is not a problem because we have not exceeded the line length 312 00:20:07,520 --> 00:20:08,353 recommendation. 313 00:20:09,590 --> 00:20:13,790 So how are you going to check if the transaction is successful? 314 00:20:14,420 --> 00:20:14,690 Well, 315 00:20:14,690 --> 00:20:19,690 if the money received is greater or equal to the cost of the drink, well in this case 316 00:20:21,770 --> 00:20:26,300 that means we should return true, right? The transaction is successful. 317 00:20:26,990 --> 00:20:30,530 And if it's not the case, if it's the opposite case, 318 00:20:30,860 --> 00:20:34,160 then we're going to print, Sorry that's not enough money. 319 00:20:34,220 --> 00:20:36,380 And the money is refunded to them. 320 00:20:36,620 --> 00:20:37,453 Right. 321 00:20:39,590 --> 00:20:44,420 So let's print that here. And we're also going to return false. 322 00:20:44,960 --> 00:20:48,340 Remember that the return has to be the last thing in your function. 323 00:20:48,400 --> 00:20:52,420 If you put this above the print statement then the print statement will never 324 00:20:52,420 --> 00:20:55,840 get called, and that's why you have this highlight. And if you click on it, 325 00:20:55,840 --> 00:20:58,810 you can see that it tells you this code is unreachable. 326 00:21:00,520 --> 00:21:04,780 So there's a lot of these little hints and tips that really help you when you're 327 00:21:04,780 --> 00:21:05,613 developing. 328 00:21:06,340 --> 00:21:10,990 But if the user has inserted enough money then the cost of the drink should be 329 00:21:10,990 --> 00:21:15,310 added to the machine as the profit so that we can see it in the next time report 330 00:21:15,310 --> 00:21:16,143 is triggered. 331 00:21:16,420 --> 00:21:21,420 So this means that if this money_received is greater or equal to the drink cost, 332 00:21:22,420 --> 00:21:27,420 then we're going to add to this variable called profit that we have up here, 333 00:21:28,870 --> 00:21:30,340 which starts out at zero, 334 00:21:30,580 --> 00:21:34,420 but we're going to add the drinks cost to profit. 335 00:21:34,720 --> 00:21:37,600 So we're going to say profit += drink_cost. 336 00:21:38,110 --> 00:21:41,740 And now you'll see an error under the profit 337 00:21:42,070 --> 00:21:45,100 because this is acting inside 338 00:21:45,130 --> 00:21:50,130 a local scope and profit is outside in the global scope. 339 00:21:50,830 --> 00:21:54,550 So in order to reach it, we have to say global profit. 340 00:21:56,260 --> 00:22:01,260 And the final part of checking the transaction is seeing if the user has 341 00:22:01,420 --> 00:22:06,070 inserted too much money then the machine is going to offer change. For example, 342 00:22:06,340 --> 00:22:11,080 here is however many dollars in change and the change should be rounded to two 343 00:22:11,080 --> 00:22:15,760 decimal places. Again, it's going to be inside this if statement. 344 00:22:16,420 --> 00:22:21,130 So the change is going to be equal to the amount of money received, 345 00:22:21,430 --> 00:22:23,740 subtracting the drink cost. 346 00:22:24,280 --> 00:22:27,430 And this of course could be any number of decimal places. 347 00:22:28,060 --> 00:22:30,040 So we can use the round function 348 00:22:30,040 --> 00:22:34,150 which you've seen a long time ago to round this number 349 00:22:34,510 --> 00:22:38,230 and the second input is the number of decimal places. 350 00:22:39,310 --> 00:22:43,270 So if you just hover over the function name, then you can see the docs come up 351 00:22:43,720 --> 00:22:48,670 and this function is basically going to around a number to a given precision in 352 00:22:48,670 --> 00:22:52,840 decimal digits. So the first is the number you want to round, 353 00:22:53,140 --> 00:22:57,850 and the second is the number of digits that you want after the dot 354 00:22:57,880 --> 00:23:02,080 basically. Now that we've gotten hold of the change, 355 00:23:02,110 --> 00:23:05,260 we're going to print and tell the user, 356 00:23:05,440 --> 00:23:09,730 basically, here is this many dollars in change. 357 00:23:11,260 --> 00:23:14,860 And of course I have to add an F to activate that fstring. 358 00:23:16,570 --> 00:23:21,010 So now we're ready to call is_transaction_successful 359 00:23:21,550 --> 00:23:25,630 and we're going to pass in the money_received and the drink_cost. 360 00:23:26,050 --> 00:23:30,280 So the money_received is, of course, going to be the payment from the previous step 361 00:23:30,730 --> 00:23:35,530 that was calculated from all the coins and the drink_cost is going to be based 362 00:23:35,530 --> 00:23:38,650 on the drink and it's under the key cost, 363 00:23:38,980 --> 00:23:43,750 which we can confirm up here. So the drink is this dictionary, 364 00:23:44,080 --> 00:23:46,550 and then there's the ingredients and the cost. 365 00:23:48,760 --> 00:23:49,030 Right. 366 00:23:49,030 --> 00:23:54,030 Let's rerun our code and let's test it out with something. Let's say 367 00:23:54,070 --> 00:23:57,100 I want a latte. Please insert coins. 368 00:23:57,280 --> 00:24:02,170 Let's say we tried to insert insufficient coins. 369 00:24:03,700 --> 00:24:07,150 It tells us, sorry, that's not enough money. Money is refunded. 370 00:24:07,660 --> 00:24:11,020 But let's try giving it enough coins this time. 371 00:24:13,750 --> 00:24:14,950 And in this case, 372 00:24:14,980 --> 00:24:19,980 it accepts it and it tells us here's $2.42 in change rounded to two decimal places, 373 00:24:21,700 --> 00:24:25,570 and we're ready to take another drink. So now if we hit report, 374 00:24:25,630 --> 00:24:30,630 you can see that we've now earned some money in our machine and all our code is 375 00:24:30,730 --> 00:24:32,440 working as expected. 376 00:24:33,550 --> 00:24:37,450 So we're now ready to tackle the final part, which is to make coffee. 377 00:24:38,050 --> 00:24:42,580 If the transaction is successful and there are enough resources to make the 378 00:24:42,580 --> 00:24:42,880 drinks 379 00:24:42,880 --> 00:24:47,350 the user selected, then the ingredients to make the drink should be deducted from 380 00:24:47,350 --> 00:24:51,010 the coffee machine's resources. For example, before I purchased a latte 381 00:24:51,070 --> 00:24:52,660 I have 300ml of water. 382 00:24:53,050 --> 00:24:57,010 After I purchased the latte that gets reduced by 200 to 100, 383 00:24:57,340 --> 00:25:00,520 and the same happens to the other ingredient values. 384 00:25:00,790 --> 00:25:04,750 But of course the money goes up because I've already taken payment in the 385 00:25:04,750 --> 00:25:08,770 previous step. Let's take this into an if statement 386 00:25:08,800 --> 00:25:13,800 because remember this function returns true when the payment is accepted or false 387 00:25:14,440 --> 00:25:15,820 if their money is insufficient. 388 00:25:16,240 --> 00:25:19,510 So this is where we're going to call on next function 389 00:25:19,540 --> 00:25:23,740 which is to make coffee. So let's create 390 00:25:23,770 --> 00:25:27,940 make_coffee. In order to make coffee 391 00:25:27,940 --> 00:25:32,940 we need to know the drink name so that we can tell the user here's your 392 00:25:33,910 --> 00:25:34,810 particular drink. 393 00:25:35,230 --> 00:25:39,130 And it will also need to have the order ingredients. 394 00:25:40,060 --> 00:25:45,060 The goal of this function is to deduct the required ingredients from the 395 00:25:46,960 --> 00:25:49,660 resources. In order to do that, 396 00:25:49,840 --> 00:25:54,840 we're going to get hold of the order ingredients and we're going to loop 397 00:25:55,900 --> 00:26:00,730 through them. So for each of the items in the order_ingredients, 398 00:26:01,630 --> 00:26:05,770 we're going to look inside the resources for that particular item 399 00:26:06,220 --> 00:26:10,570 and we're going to subtract the amount that's in the order_ingredients. 400 00:26:11,620 --> 00:26:14,410 And once all of that is done, so the for loop 401 00:26:14,440 --> 00:26:19,440 ends, then we can print and we can even add an emoji to this. 402 00:26:21,160 --> 00:26:21,993 Right. 403 00:26:22,390 --> 00:26:22,930 On a Mac 404 00:26:22,930 --> 00:26:27,850 you can insert an emoji by going to edit, emoji, and symbols. On Windows 405 00:26:27,850 --> 00:26:32,560 the easiest thing to do is to just search Google for a coffee emoji 406 00:26:32,890 --> 00:26:35,200 and then copy and paste it into your code. 407 00:26:35,860 --> 00:26:40,060 So now let's call make_coffee here and notice how 408 00:26:40,240 --> 00:26:42,940 if we are here the machine is on 409 00:26:44,250 --> 00:26:47,610 and it's not any of these other previous choices, 410 00:26:48,270 --> 00:26:52,530 and then the resource is sufficient and the transaction is successful. 411 00:26:52,560 --> 00:26:57,560 These are all the steps that it took us to get to this particular stage in our 412 00:26:57,630 --> 00:26:58,463 code. 413 00:26:58,680 --> 00:27:02,790 So now we're going to make the coffee and we're going to pass in two things. 414 00:27:02,820 --> 00:27:06,900 So let's just see the prompt again. We need to give the drink name 415 00:27:06,960 --> 00:27:11,960 which is going to be the choice that the user entered, and the order ingredients 416 00:27:12,060 --> 00:27:16,260 which is going to come from the drink and it's under the key ingredients. 417 00:27:17,700 --> 00:27:21,810 So now we're ready to test and run our code once more. 418 00:27:22,230 --> 00:27:26,340 Let's say, I want a latte and I'm going to insert lots of money. 419 00:27:27,180 --> 00:27:31,200 And now I have my latte. If I hit report, 420 00:27:31,350 --> 00:27:36,150 you should be able to see that a bunch of resources were subtracted and the 421 00:27:36,150 --> 00:27:40,800 money is increased. If I try to order another latte, 422 00:27:40,830 --> 00:27:45,750 it should fail because there is not enough water and there's not enough milk. 423 00:27:46,620 --> 00:27:51,030 You can see that it's not going to let me go through as long as one of the 424 00:27:51,030 --> 00:27:52,770 ingredients is not enough. 425 00:27:54,390 --> 00:27:59,070 So we've now managed to fulfill all of the requirements of our coffee machine 426 00:27:59,100 --> 00:28:00,450 program. Now, 427 00:28:00,450 --> 00:28:04,620 this probably a lot more complexity that you could add to your coffee machine, 428 00:28:05,010 --> 00:28:10,010 but basically what I wanted to show you today is how you would program something 429 00:28:11,160 --> 00:28:12,660 that exists in real life, 430 00:28:12,690 --> 00:28:17,690 like a coffee machine and even something that seems as simple as a coffee 431 00:28:18,030 --> 00:28:20,760 machine. It can lead to a lot of errors, 432 00:28:20,790 --> 00:28:25,080 a lot of bugs and a lot of anguish, but its good. 433 00:28:25,080 --> 00:28:26,370 The more that you struggle, 434 00:28:26,670 --> 00:28:31,170 the closer you get towards your goals. And the clearer the role of the function, 435 00:28:31,560 --> 00:28:35,100 the easier it will be for you to untangle the logic. 436 00:28:36,480 --> 00:28:39,990 If you want to take a look at the completed code that I've written in this 437 00:28:39,990 --> 00:28:40,823 lesson, 438 00:28:40,860 --> 00:28:45,000 then simply head over to the link that's in the resources and you'll be able to 439 00:28:45,000 --> 00:28:45,720 see it in 440 00:28:45,720 --> 00:28:50,700 Repl.it. Make sure that you've managed to fix any issues in your code 441 00:28:51,060 --> 00:28:56,060 and that it runs exactly the same way as expected in the program requirements.