1 00:00:00,250 --> 00:00:03,910 One of the first things I want to talk about is randomisation. 2 00:00:04,390 --> 00:00:07,930 And this is a concept that we're super familiar with. 3 00:00:08,530 --> 00:00:10,690 Randomization is really, 4 00:00:10,690 --> 00:00:14,890 really important when we want to create computer programs that have a degree of 5 00:00:14,950 --> 00:00:19,540 unpredictability. Now, the biggest category of that is, of course, games right? 6 00:00:19,840 --> 00:00:23,440 Can you imagine if you had to play Tetris and every single time, 7 00:00:23,440 --> 00:00:25,780 the block that fell down was like predictable. 8 00:00:26,020 --> 00:00:30,430 You always knew that it was going to be a T and then it was going to be an L 9 00:00:30,460 --> 00:00:32,439 like, there would be no fun in that right? 10 00:00:32,770 --> 00:00:37,770 So how do we create this randomness for our programs? Now in nature and in our 11 00:00:38,950 --> 00:00:42,460 everyday lives, it's really easy to create randomness. 12 00:00:42,760 --> 00:00:46,480 If you splash some paint on a canvas, that's going to be pretty random. 13 00:00:46,600 --> 00:00:51,340 If you take a look at the TV static from the analog TVs, 14 00:00:51,610 --> 00:00:53,890 that's also a whole bunch of randomness there. 15 00:00:54,370 --> 00:00:56,440 But when we're talking about computers, 16 00:00:56,740 --> 00:01:00,670 then these machines are what we would call deterministic. 17 00:01:00,910 --> 00:01:05,910 They will perform repeatable actions in a fully predictable way. 18 00:01:06,400 --> 00:01:11,400 So how do we wrangle these machines that operate basically on ones and zeros to 19 00:01:11,920 --> 00:01:15,280 get them to create some random numbers? Well, 20 00:01:15,280 --> 00:01:19,150 there's a whole bunch of maths that can be applied to create what are called a 21 00:01:19,180 --> 00:01:21,490 pseudo-random number generators. 22 00:01:21,910 --> 00:01:25,420 And the one that Python uses is something called the Mersenne Twister. 23 00:01:25,900 --> 00:01:28,180 And if you really want to read about it, 24 00:01:28,210 --> 00:01:32,020 then you can have a look on Wikipedia and take a look under the algorithmic 25 00:01:32,020 --> 00:01:36,310 detail. But to be honest, it's a little bit too much information for anybody, 26 00:01:36,670 --> 00:01:41,050 unless you're really interested in these types of number generators. 27 00:01:41,560 --> 00:01:43,000 But what I recommend though, 28 00:01:43,000 --> 00:01:47,980 is a free video from the Khan Academy where they explain pseudorandom number 29 00:01:47,980 --> 00:01:50,950 generators, and it's really well produced. 30 00:01:50,980 --> 00:01:55,980 And it tells you a lot of different aspects of pseudorandom number generation. 31 00:01:57,010 --> 00:01:57,790 Have a look at that 32 00:01:57,790 --> 00:02:02,020 if you're interested to learn a little bit more about pseudorandom number 33 00:02:02,020 --> 00:02:05,650 generators. We've talked a lot about randomness, 34 00:02:05,710 --> 00:02:07,180 but lets see it in action. 35 00:02:07,210 --> 00:02:11,980 Let's write some code and produce some random numbers. Head over to the Day 4 36 00:02:11,980 --> 00:02:15,340 starting Repl and then go ahead and fork your own copy. 37 00:02:15,760 --> 00:02:18,970 We know that we want to get hold of some random numbers, 38 00:02:19,300 --> 00:02:23,950 but we don't really want to implement the Mersenne Twister ourselves because 39 00:02:24,220 --> 00:02:28,480 it's horrendously complicated using lots and lots of math and probably it'll 40 00:02:28,480 --> 00:02:33,250 take us months to write the code for. So how can we get random numbers? 41 00:02:33,880 --> 00:02:37,870 If you think about it, it's a little bit like searching for something in Google. 42 00:02:38,530 --> 00:02:43,530 The Google algorithm is horrendously complicated and it's taken them years and 43 00:02:43,660 --> 00:02:48,370 years to refine and perfect to such an extent where I think Google knows me 44 00:02:48,370 --> 00:02:50,980 better than myself because when I search for something, 45 00:02:50,980 --> 00:02:53,410 it always gives me the most relevant results. 46 00:02:53,920 --> 00:02:57,760 And if you're questioning the complexity of the Google algorithm, 47 00:02:58,090 --> 00:03:02,980 just go to Bing and try searching for something and see how relevant the results 48 00:03:02,980 --> 00:03:06,100 are. So they have the super complex algorithm, 49 00:03:06,130 --> 00:03:09,340 which we're never going to get a chance to see, let alone understand. 50 00:03:09,850 --> 00:03:14,850 And yet every day we're able to search things on Google and use this Google 51 00:03:15,100 --> 00:03:17,680 algorithm to get the things that we want, 52 00:03:18,010 --> 00:03:21,640 like the air speed velocity of a laden swallow. 53 00:03:22,240 --> 00:03:26,920 Now we can do the same thing when we want to generate random numbers. Because 54 00:03:26,920 --> 00:03:29,410 this is such frequently needed functionality, 55 00:03:29,710 --> 00:03:33,190 the Python team have already created a random module. 56 00:03:33,700 --> 00:03:38,700 So if you head over to askpython.com and search for the Python random module, 57 00:03:39,100 --> 00:03:42,700 then you'll be able to see the documentation for this random module. 58 00:03:43,180 --> 00:03:46,750 And you can see that it contains a whole bunch of functions that you can use 59 00:03:47,170 --> 00:03:50,110 that allows you to generate random integers, 60 00:03:50,110 --> 00:03:53,650 so random whole numbers or random floating point numbers. 61 00:03:54,040 --> 00:03:59,040 So let's see how we can tap into this random module. In order to tap into the 62 00:03:59,260 --> 00:04:02,410 random module, we first have to import it. 63 00:04:02,440 --> 00:04:07,440 So we write import random. And now we're able to use this random module in our 64 00:04:10,000 --> 00:04:11,800 main.py code. 65 00:04:12,580 --> 00:04:17,470 We can start using the documentation to generate a random integer. For example, 66 00:04:17,709 --> 00:04:22,710 they show us in the code snippet here that we could generate a random integer by 67 00:04:23,320 --> 00:04:27,430 using the randint function, providing an a and B. 68 00:04:27,850 --> 00:04:31,480 And it will return a random integer between a and b, 69 00:04:31,630 --> 00:04:33,700 including both of those numbers. 70 00:04:34,150 --> 00:04:37,390 And there's even a little bit of code snippet to show us how it's done. 71 00:04:37,720 --> 00:04:42,720 So this line of code generates a random whole number between 100 and 200 and 72 00:04:44,110 --> 00:04:48,310 including those two numbers. So it could be anything between those two numbers. 73 00:04:49,060 --> 00:04:51,340 So let's see if we can implement this in our code. 74 00:04:51,820 --> 00:04:56,820 Let's say that we want to create a random integer and we use the same code that 75 00:04:56,950 --> 00:04:59,650 we saw in the code snippet where we say random, 76 00:04:59,890 --> 00:05:04,600 that's tapping into this module here, .randint. 77 00:05:04,960 --> 00:05:09,960 And then we at a set of parentheses and then we specify the start, and 78 00:05:10,360 --> 00:05:11,350 then the end. 79 00:05:11,830 --> 00:05:16,830 So this is basically a range of numbers that we're specifying, any integer 80 00:05:16,960 --> 00:05:18,670 between 1 and 10. 81 00:05:19,480 --> 00:05:24,480 And now we can go ahead and print our random integer, just like that. 82 00:05:26,050 --> 00:05:28,060 And every single time I run it, 83 00:05:28,330 --> 00:05:32,050 you'll notice that I'll get a different number or maybe sometimes the same, 84 00:05:32,140 --> 00:05:35,650 but it's a random number between the range that I've specified. 85 00:05:37,000 --> 00:05:41,890 Now I've mentioned that the random module is a Python module. 86 00:05:41,980 --> 00:05:44,860 So what exactly is a module? Well, 87 00:05:44,890 --> 00:05:49,480 you've seen that we've mostly been writing our code all on the same page in a 88 00:05:49,480 --> 00:05:50,920 sort of script style, right? 89 00:05:50,920 --> 00:05:53,980 And everything just kind of gets executed from top to bottom. 90 00:05:54,460 --> 00:05:58,490 But sometimes your code will get so long because you're trying to create 91 00:05:58,490 --> 00:06:03,490 something complicated and it's no longer possible to understand what's going on 92 00:06:03,620 --> 00:06:06,140 in such a large piece of code. 93 00:06:06,650 --> 00:06:11,650 What people will do in that case is to split the code up into individual modules 94 00:06:13,190 --> 00:06:18,190 where each module is responsible for a different bit of functionality of your 95 00:06:18,380 --> 00:06:22,430 program. And if you have a complex project with many, many modules, 96 00:06:22,700 --> 00:06:25,520 then you could have collaboration on your project, right? 97 00:06:25,550 --> 00:06:29,630 Lots of people could be working on it, each person working on a different thing. 98 00:06:29,990 --> 00:06:31,820 Say if a factory was building a car, 99 00:06:32,150 --> 00:06:36,260 it wouldn't make sense for one person to build the entire car from wheels, 100 00:06:36,260 --> 00:06:38,810 axles to chassis, that's crazy. 101 00:06:38,960 --> 00:06:43,220 Instead you have different people working on different modules like the tire 102 00:06:43,220 --> 00:06:47,000 module or the chassis module or the engine module. 103 00:06:47,420 --> 00:06:49,220 And then once they put everything together, 104 00:06:49,490 --> 00:06:53,990 you end up with the final car or in our case, the final program. 105 00:06:54,740 --> 00:06:59,570 So we know that the random module is a module that the Python team created to 106 00:06:59,570 --> 00:07:04,570 make it easier for us to generate our random numbers without needing to get into 107 00:07:04,850 --> 00:07:09,850 the complexities of all of the math that's required to generate pseudorandom 108 00:07:09,920 --> 00:07:10,753 numbers. 109 00:07:10,970 --> 00:07:15,080 But how can we create our own modules and how do modules work anyways? 110 00:07:15,260 --> 00:07:19,430 Well, it's actually very simple. If you go ahead and click on the files icon, 111 00:07:19,490 --> 00:07:23,120 you can see, we currently only have one file that we're writing in, 112 00:07:23,420 --> 00:07:25,100 which is main.py, 113 00:07:25,130 --> 00:07:29,150 the Python file. And the main.py is the entry point to our program. 114 00:07:29,300 --> 00:07:33,590 This is the file that will be executed when we run our code. Now, 115 00:07:33,590 --> 00:07:37,100 if I go ahead and click on this icon to add a new file, 116 00:07:37,490 --> 00:07:42,490 let's say I call it my_module.py and I create a new Python file. 117 00:07:45,650 --> 00:07:50,270 And inside my module, I'm going to maybe work on something else. 118 00:07:50,300 --> 00:07:53,270 Let's say I want into the store, the value of PI. 119 00:07:55,850 --> 00:07:57,260 Okay. I think that's all I remember. 120 00:07:57,680 --> 00:08:02,360 So I know the value of PI and I want to be able to use it in my different 121 00:08:02,360 --> 00:08:06,080 programs. Now that I've created my_module.py, well, 122 00:08:06,080 --> 00:08:11,080 now I can use my module wherever I want just by importing it. So I could import 123 00:08:13,250 --> 00:08:17,480 my_module. And now down here, I can say, 124 00:08:17,900 --> 00:08:22,900 let's go ahead and print my_module.pi. 125 00:08:24,440 --> 00:08:28,610 And now if I go ahead and comment out of this code and hit run, 126 00:08:29,060 --> 00:08:29,810 then you'll see, 127 00:08:29,810 --> 00:08:34,809 we get that value of PI that got dragged in because I imported my module, 128 00:08:35,780 --> 00:08:40,370 but now we've got our code separated out into separate modules that are 129 00:08:40,370 --> 00:08:42,110 responsible for different things. 130 00:08:42,650 --> 00:08:46,460 And that is how the random module works as well. 131 00:08:46,880 --> 00:08:51,590 So I'm going to go ahead and delete all of this stuff relating to PI, 132 00:08:51,890 --> 00:08:55,500 but you can keep yours if you want, if you wanna keep it for reference. 133 00:08:57,390 --> 00:08:59,910 Coming back to creating random numbers. 134 00:09:00,300 --> 00:09:03,840 We've seen how we can create random whole numbers, 135 00:09:04,080 --> 00:09:08,730 but what if I wanted to create a random floating point number? Well, 136 00:09:08,730 --> 00:09:12,390 it tells me how to do it in the AskPython documentation. 137 00:09:12,780 --> 00:09:17,780 And all I have to do is use the random module that contains the random function 138 00:09:18,180 --> 00:09:23,180 and it will return a random floating-point number between 0 and 1. 139 00:09:24,480 --> 00:09:29,130 But it's really important to note that in this case it doesn't actually include 140 00:09:29,130 --> 00:09:34,050 1. So it goes up to like 0.9999999, but not including 1. 141 00:09:34,590 --> 00:09:36,150 Let's go ahead and try that out. 142 00:09:36,510 --> 00:09:41,190 So we'll say random_float = random.random 143 00:09:41,250 --> 00:09:45,990 and then I set of parentheses. And this will give me output some sort of number 144 00:09:46,320 --> 00:09:50,040 in the interval between 0 and 1, but not including 1. 145 00:09:50,910 --> 00:09:53,430 So let's go ahead and see if it works. 146 00:09:56,820 --> 00:09:57,210 First, 147 00:09:57,210 --> 00:10:01,650 we print a random integer between 1 and 10 and then we print our random float 148 00:10:01,710 --> 00:10:06,210 between 0 and 1. And every time we run the code, 149 00:10:06,240 --> 00:10:09,210 you'll notice that we get different random numbers. 150 00:10:10,290 --> 00:10:11,610 Now here's a question. 151 00:10:12,420 --> 00:10:17,420 This random function always generates a number between 0 and 1 and it has 152 00:10:18,210 --> 00:10:19,560 many decimal places. 153 00:10:20,160 --> 00:10:25,050 But what if I wanted a random floating-point number between 0 and 5? 154 00:10:25,980 --> 00:10:28,620 How might we do that? Now 155 00:10:28,680 --> 00:10:33,510 it's not as complicated as you think it is and you'll be able to do it just by 156 00:10:33,510 --> 00:10:35,190 looking at the code you've got here. 157 00:10:35,880 --> 00:10:39,210 Have a think about it and see if you can come up with the answer. 158 00:10:39,330 --> 00:10:42,420 I'll go through it with you afterwards. Pause the video now and give that a go. 159 00:10:44,430 --> 00:10:44,850 All right. 160 00:10:44,850 --> 00:10:49,850 So we know that this random float can be anything between 161 00:10:50,230 --> 00:10:51,300 0.000000 162 00:10:51,370 --> 00:10:56,370 to 0.999999..., effectively repeating right? Now 163 00:10:58,050 --> 00:11:03,050 what if we were able to multiply this random number by a number? 164 00:11:05,970 --> 00:11:10,620 Let's say that I multiply the random_float by 5. 165 00:11:11,310 --> 00:11:15,150 Well, what if this random_float was no 0.1? Well, 166 00:11:15,180 --> 00:11:19,050 0.1 times 5 would be 0.5. 167 00:11:20,070 --> 00:11:25,070 But what if the random_float was 0.4? 0.4 times 5 would be 2. 168 00:11:28,290 --> 00:11:30,090 Or what if it was 0.9? 169 00:11:30,120 --> 00:11:33,330 0.9 times five is 4.5. 170 00:11:33,840 --> 00:11:38,840 So effectively by multiplying this random_float by 5, 171 00:11:39,840 --> 00:11:42,540 I will end up with random numbers, 172 00:11:42,810 --> 00:11:46,920 but of course they're now floats, right? So it could be 0.000 173 00:11:46,920 --> 00:11:50,940 ... all the way to 4.999999 174 00:11:51,360 --> 00:11:53,010 and et cetera, et cetera. 175 00:11:53,410 --> 00:11:58,410 So this is how we can expand that range from 0 to 1 all the way to 0 to 176 00:11:59,650 --> 00:12:02,050 5, but not including 5. 177 00:12:03,130 --> 00:12:05,950 So what can you do with random numbers? Well, 178 00:12:06,010 --> 00:12:10,870 if we think back to our love calculator that we made in the last lesson, 179 00:12:11,380 --> 00:12:15,070 um, I mean, its kind of based on pseudo-science right? 180 00:12:15,070 --> 00:12:20,050 Like just because you have a certain number of letters that exist in the word 181 00:12:20,050 --> 00:12:20,890 true and love, 182 00:12:20,890 --> 00:12:24,160 it doesn't mean that you're actually going to be more compatible. 183 00:12:24,950 --> 00:12:29,590 I'm sorry to break anyone's heart out there. But if it's random anyways, 184 00:12:29,620 --> 00:12:34,270 then why don't we just use a random number generator saving ourselves all of 185 00:12:34,270 --> 00:12:37,510 that trouble from counting Ts and counting Us. 186 00:12:37,900 --> 00:12:42,900 We can instead just simply say love_score = random.randint between 187 00:12:47,830 --> 00:12:52,830 1 and 100. And then go ahead and just print "Your love score is", 188 00:12:56,620 --> 00:13:01,420 and then let's insert our love score and turn this into an Fstring. 189 00:13:02,230 --> 00:13:06,310 Let's print that. And you can see that we're getting a different love score 190 00:13:06,340 --> 00:13:10,540 every single time I run this code. It's between 1 and a hundred 191 00:13:10,660 --> 00:13:12,400 and you know, 192 00:13:12,520 --> 00:13:16,300 who can tell that this is any different from the previous method, right? 193 00:13:16,660 --> 00:13:21,490 So we can use our random number generator for this. We can use it for, 194 00:13:21,520 --> 00:13:22,180 um, 195 00:13:22,180 --> 00:13:27,180 creating a dice or flipping a coin or we can use it in games that we create. 196 00:13:28,540 --> 00:13:33,010 If you head over to the next lesson, I've got a code challenge for you 197 00:13:33,310 --> 00:13:37,990 where you are going to be building a program in order to pick from heads or 198 00:13:37,990 --> 00:13:42,990 tails and help the user out when they don't have access to a coin. For all of 199 00:13:43,030 --> 00:13:45,280 that and more, I'll see you on the next lesson.