WEBVTT 0 00:00.140 --> 00:04.100 One of the first things I want to talk about is randomization. 1 00:04.100 --> 00:08.180 And this is a concept that we're super familiar with. 2 00:08.300 --> 00:14.540 Randomization is really, really important when we want to create computer programs that have a degree 3 00:14.540 --> 00:16.100 of unpredictability. 4 00:16.130 --> 00:19.100 Now the biggest category of that is of course, games. 5 00:19.100 --> 00:19.610 Right? 6 00:19.610 --> 00:21.710 Can you imagine if you had to play Tetris, 7 00:21.710 --> 00:27.170 and every single time the block that fell down was like predictable? You always knew that it was going 8 00:27.170 --> 00:32.510 to be a T, and then it was going to be an L, like there would be no fun in that, right? 9 00:32.510 --> 00:39.770 So how do we create this randomness for our programs? Now in nature and in our everyday lives, 10 00:39.770 --> 00:42.560 it's really easy to create randomness. 11 00:42.560 --> 00:46.490 If you splash some paint on a canvas, that's going to be pretty random. 12 00:46.490 --> 00:54.110 If you take a look at the TV static from the analog TVs, that's also a whole bunch of randomness there. 13 00:54.110 --> 01:00.740 But when we're talking about computers, then these machines are what we would call deterministic. 14 01:00.740 --> 01:06.140 They will perform repeatable actions in a fully predictable way. 15 01:06.140 --> 01:13.490 So how do we wrangle these machines that operate basically on 1's and 0's to get them to create some 16 01:13.490 --> 01:14.750 random numbers? 17 01:14.750 --> 01:20.680 Well, there's a whole bunch of maths that can be applied to create what are called Pseudo Random Number 18 01:20.680 --> 01:21.610 Generators. 19 01:21.610 --> 01:25.570 And the one that Python uses is something called the Mersenne Twister. 20 01:25.570 --> 01:31.150 And if you really want to read about it, then you can have a look on Wikipedia and take a look under 21 01:31.150 --> 01:32.710 the Algorithmic detail. 22 01:32.710 --> 01:38.470 But to be honest, it's a little bit too much information for anybody, unless you're really interested 23 01:38.470 --> 01:41.260 in these types of number generators. 24 01:41.260 --> 01:47.650 But what I recommend, though, is a free video from the Khan Academy where they explain Pseudorandom 25 01:47.650 --> 01:55.180 Number Generators and it's really well produced, and it tells you a lot of different aspects of pseudorandom 26 01:55.180 --> 01:56.500 number generation. 27 01:56.500 --> 01:57.730 So have a look at that, 28 01:57.730 --> 02:02.860 if you're interested to learn a little bit more about Pseudorandom Number Generators. 29 02:03.130 --> 02:07.150 We've talked a lot about randomness, but let's see it in action. 30 02:07.150 --> 02:10.150 Let's write some code and produce some random numbers. 31 02:10.150 --> 02:16.570 We know that we want to get hold of some random numbers, but we don't really want to implement the 32 02:16.570 --> 02:22.330 Mersenne Twister ourselves because it's horrendously complicated, using lots and lots of maths, 33 02:22.330 --> 02:25.450 and probably it'll take us months to write the code for. 34 02:25.810 --> 02:28.090 So how can we get random numbers? 35 02:28.360 --> 02:32.830 If you think about it, it's a little bit like searching for something in Google. 36 02:32.830 --> 02:39.460 The Google algorithm is horrendously complicated, and it's taken them years and years to refine and 37 02:39.460 --> 02:44.110 perfect to such an extent where I think Google knows me better than myself, 38 02:44.110 --> 02:48.280 because when I search for something, it always gives me the most relevant results. 39 02:48.280 --> 02:55.060 And if you're questioning the complexity of the Google algorithm, just go to Bing and try searching 40 02:55.060 --> 02:58.030 for something and see how relevant the results are. 41 02:58.060 --> 03:03.220 So they have this super complex algorithm, which we're never going to get a chance to see, let alone 42 03:03.220 --> 03:04.240 understand. 43 03:04.270 --> 03:11.680 And yet, every day we're able to search things on Google and use this Google algorithm to get the things 44 03:11.680 --> 03:16.540 that we want, like the air speed velocity of a laden swallow. 45 03:16.660 --> 03:21.000 Now we can do the same thing when we want to generate random numbers. 46 03:21.000 --> 03:27.270 Because this is such frequently needed functionality, the Python team have already created a Random 47 03:27.270 --> 03:34.050 Module, and you can get a direct link to this documentation just by clicking on the link in the Description 48 03:34.050 --> 03:39.720 box here. And you can see that it contains a whole bunch of functions that you can use that allows 49 03:39.720 --> 03:42.000 you to generate random integers. 50 03:42.000 --> 03:45.720 So random whole numbers, or random floating point numbers. 51 03:45.720 --> 03:49.290 So let's see how we can tap into this Random Module. 52 03:49.740 --> 03:51.900 We first have to import it. 53 03:51.900 --> 03:54.510 So we write, "import random". 54 03:55.290 --> 04:00.840 And now we're able to use this Random Module in our Python code. 55 04:01.230 --> 04:07.920 So we can look into the documentation to figure out how we can generate random whole numbers, 56 04:07.920 --> 04:13.830 to random integers using this Random Module from Python. 57 04:13.830 --> 04:21.390 So if you scroll down on this documentation file and you go to the section, Functions for integers, 58 04:21.390 --> 04:27.690 then you can see a whole bunch of different things that we can do to generate random whole numbers. 59 04:27.690 --> 04:32.880 Now the one that we're going to look into is random.randint(). 60 04:32.880 --> 04:38.400 And this is going to generate a random integer between a and b. 61 04:38.400 --> 04:42.870 And these are the numbers that we have to provide to set that range. 62 04:42.870 --> 04:52.260 So the way that randint(a, b) works is that it will generate a random number that is greater than or equal 63 04:52.260 --> 04:56.600 to a and less than or equal to b. 64 04:56.600 --> 05:05.030 So basically, between this range a and b that we provide, but inclusive of both a and b. 65 05:05.030 --> 05:06.980 So let's give it a go. 66 05:07.070 --> 05:11.840 If we go into our code file and we use the Random Module. 67 05:11.840 --> 05:13.610 So we first write, "random". 68 05:13.610 --> 05:21.020 This refers to this module that we just imported which contains all the code for generating random numbers. 69 05:21.020 --> 05:26.210 And then we write a full stop, which in programming is normally called a dot. 70 05:26.210 --> 05:28.010 So random. 71 05:28.010 --> 05:32.990 and then we're going to use the name of that function that we found, randint. 72 05:33.140 --> 05:36.920 So this randint needs some open parentheses, 73 05:36.920 --> 05:44.000 and you can see from the code hints it's asking us for a which is an integer, and b which is an integer, 74 05:44.000 --> 05:47.330 and we already know this is the range that we want. 75 05:47.330 --> 05:49.490 So let's go ahead and give it a range. 76 05:49.490 --> 05:53.960 And I want a random whole number between 1 and 10. 77 05:54.200 --> 06:00.140 So in this case I've got 1 as the first starting value. 78 06:00.140 --> 06:03.410 So it's going to give me a random number that could include 1, 79 06:03.410 --> 06:07.910 and then it goes up to 10 and including 10. 80 06:07.910 --> 06:12.380 So it means that we will get random numbers between 1 and 10. 81 06:12.380 --> 06:20.570 So let's go ahead and save this into a variable which we'll call, random_integer. 82 06:21.410 --> 06:25.850 And now I'm going to print this random_integer. 83 06:26.030 --> 06:30.740 And every single time I run it, you'll notice that I'll get a different number, 84 06:30.740 --> 06:36.200 or maybe sometimes the same, but it's a random number between the range that I've specified. 85 06:37.040 --> 06:42.260 Now, I've mentioned that the Random M odule is a Python module. 86 06:42.260 --> 06:44.540 So what exactly is a module? 87 06:44.570 --> 06:50.570 Well, you've seen that we've mostly been writing our code all on the same page in a sort of script 88 06:50.570 --> 06:50.990 style, 89 06:50.990 --> 06:51.200 right? 90 06:51.200 --> 06:54.500 And everything just kind of gets executed from top to bottom. 91 06:54.500 --> 07:01.000 But sometimes your code will get so long because you're trying to create something complicated, and 92 07:01.000 --> 07:06.700 it's no longer possible to understand what's going on in such a large piece of code. 93 07:06.730 --> 07:14.650 What people will do in that case is to split the code up into individual modules, where each module 94 07:14.650 --> 07:21.530 is responsible for a different bit of functionality of your program, and if you have a complex project 95 07:21.530 --> 07:25.910 with many, many modules, then you could have collaboration on your project, right? 96 07:25.910 --> 07:31.310 Lots of people could be working on it, each person working on a different thing. Say if a factory was 97 07:31.310 --> 07:37.250 building a car, it wouldn't make sense for one person to build the entire car from wheels to axles 98 07:37.250 --> 07:38.000 to the chassis. 99 07:38.000 --> 07:39.230 That's crazy. 100 07:39.230 --> 07:45.310 Instead, you have different people working on different modules, like the Tire module, or the Chassis 101 07:45.310 --> 07:51.460 Module, or the Engine Module, and then once they put everything together, you end up with the final 102 07:51.460 --> 07:54.520 car or in our case, the final program. 103 07:54.820 --> 08:01.300 So we know that the Random Module is a module that the Python team created to make it easier for us 104 08:01.300 --> 08:07.870 to generate our random numbers without needing to get into the complexities of all of the math that's 105 08:07.870 --> 08:11.020 required to Generate Pseudorandom Numbers. 106 08:11.020 --> 08:15.490 But how can we create our own modules, and how do modules work anyways? 107 08:15.520 --> 08:17.230 Well, it's actually very simple. 108 08:17.380 --> 08:25.630 If you open up the file inspector over here and you go into today's task, Random Module and you right-click 109 08:25.630 --> 08:32.110 click on it, you can go into New and we're going to create a new Python file. 110 08:32.110 --> 08:39.180 Now we're going to create our Python file and call it my_module, so that I can show you how to create 111 08:39.180 --> 08:40.920 your very own module. 112 08:41.340 --> 08:49.590 Now let's say inside my_module, I decide to create a variable called my_favorite number, 113 08:49.590 --> 08:53.430 and it happens to be 3.1415. 114 08:53.460 --> 09:01.680 Now, if I want to use this number that I've created in my_module, all I have to do is to go back into 115 09:01.680 --> 09:07.530 the task.py, which is the main entry point, at least in this course format. 116 09:07.530 --> 09:14.310 And normally when you're writing code in Python, it might be called something like main.py or app.py, 117 09:14.310 --> 09:21.330 but either way, there's usually a primary file that you use where you write most of your starting and 118 09:21.330 --> 09:22.410 core code. 119 09:22.440 --> 09:30.060 Now, if I want to use the code in my_module, all I have to do is, same as the Random Module, 120 09:30.060 --> 09:31.350 I have to import it. 121 09:31.350 --> 09:35.880 So I'll import my_module into this task.py file. 122 09:35.880 --> 09:39.750 And then I can use it by simply printing, 123 09:39.750 --> 09:44.730 for example, my_module.my_favorite_number. 124 09:44.730 --> 09:48.360 And you can see it's exactly the same way as the Random Module, 125 09:48.360 --> 09:53.550 we imported it and then we used a function inside it called, randint. 126 09:53.550 --> 09:57.270 And now if I go ahead and print, you can see the, 127 09:57.270 --> 10:02.610 my_favorite_number is printed by using and tapping into this module. 128 10:03.180 --> 10:10.230 Now coming back to our main task of generating random numbers, let's take a look how we can generate 129 10:10.230 --> 10:12.510 random floating point numbers. 130 10:12.510 --> 10:17.790 So I'm going to go ahead and delete my module and all the related code. 131 10:17.790 --> 10:23.790 You can keep yours if you want just for revision, but I want to keep everything as clean as possible. 132 10:23.790 --> 10:30.780 So I'm also going to comment out this section where we've got the random_integer as well. 133 10:30.780 --> 10:34.520 So how do we create random floating point numbers? 134 10:34.550 --> 10:37.340 Well, let's take a look at the documentation. 135 10:37.340 --> 10:44.840 If you scroll down to this area called Real-valued distributions, you can see that one way of generating 136 10:44.840 --> 10:50.120 random floating point numbers is using the random.random() function. 137 10:50.120 --> 10:56.570 And this is one of the core functions that we use a lot when we're dealing with random numbers in Python, 138 10:56.570 --> 11:00.020 because it is one of the most adaptive functions. 139 11:00.020 --> 11:06.530 It generates a random floating point number between 0 and 1. 140 11:06.530 --> 11:12.650 Now if you look at these symbols, you'll see that the random number that's generated can be greater 141 11:12.650 --> 11:13.940 or equal to zero. 142 11:13.940 --> 11:17.540 So that means zero is included in the possibility, 143 11:17.540 --> 11:19.430 but it is less than one. 144 11:19.430 --> 11:24.620 So one is not um in the generated random numbers. 145 11:24.800 --> 11:26.600 Now let's try that out. 146 11:26.600 --> 11:33.950 So we will create a random_number_0_to_1. 147 11:33.950 --> 11:39.110 And this is going to be set to random.random. 148 11:39.110 --> 11:44.240 And notice that it's actually exactly the same, spelled the same, same casing, 149 11:44.240 --> 11:49.550 but the first one refers to the Module, and when you hover over it, it should show you it's the Module 150 11:49.550 --> 11:54.680 random, and the second one refers to the function random. 151 11:54.680 --> 11:58.160 And this is something that doesn't take any inputs, 152 11:58.160 --> 12:03.470 and all you need to do is to add an empty set of parentheses to activate it. 153 12:03.470 --> 12:10.100 When we're looking at functions such as the randint(), we always see a set of parentheses, and it's 154 12:10.100 --> 12:17.530 been used to put in inputs like what to print or what is the prompt for input, or what is the range 155 12:17.530 --> 12:18.700 for a random integer, 156 12:18.700 --> 12:25.720 but remember that some functions don't take any inputs at all, but they still need the set of parentheses 157 12:25.720 --> 12:30.880 in order to carry out the action that the function is supposed to perform. 158 12:30.880 --> 12:39.460 So let's go ahead and print this new random_number_0_to_1, and you will see that every time I press 159 12:39.460 --> 12:43.510 the print button, it generates a new floating point number, 160 12:43.510 --> 12:49.990 and it's between 0 inclusive and up to 1, not inclusive. 161 12:49.990 --> 12:57.580 So you can use this random number generator, random.random() to expand it. 162 12:57.580 --> 12:58.870 So what do I mean by that? 163 12:58.870 --> 13:06.250 If we multiply this by 10, then you'll see that the numbers that are generated are going to be between 164 13:06.250 --> 13:15.880 0 to 10 and not inclusive of 10, because we're basically multiplying the lower range 0 by 10, 165 13:15.880 --> 13:20.410 which is 0, and the upper range by 10, 1 * 10 is 10. 166 13:20.410 --> 13:27.940 So then we've shifted this random number generator to create floating point numbers between 0 and 167 13:27.940 --> 13:30.190 whatever it is that we desire. 168 13:31.150 --> 13:38.080 So you can have a play around with that, but you might also discover another function if you look through 169 13:38.080 --> 13:43.450 the documentation, which is a Random Floating Point Number Generator. 170 13:43.450 --> 13:46.600 So I'm going to call this variable, random_float. 171 13:46.600 --> 13:51.880 And I'm going to use the random.uniform() function. 172 13:51.880 --> 14:01.570 And this function will return a random floating point number such that the number is greater than or 173 14:01.570 --> 14:08.260 equal to the lower bound and less than or equal to the upper bound. 174 14:08.260 --> 14:14.820 So basically it's going to generate numbers between a and b, inclusive of a and b. 175 14:16.050 --> 14:19.920 So to use that we would say, random.uniform() 176 14:19.920 --> 14:24.600 and then we can provide a number say 1 to 10 again. 177 14:24.600 --> 14:31.980 And then let's print this random_float...and let me comment out the other part. 178 14:32.070 --> 14:37.380 And now when I run this you can see it almost does the same thing. 179 14:37.380 --> 14:45.690 The only difference is it's not entirely sure depending on rounding, whether if you will get 10 or 180 14:45.690 --> 14:48.180 not in the random_float. 181 14:48.180 --> 14:52.320 But if you want to be really sure of the range, 182 14:52.830 --> 15:01.530 so this is known as a semi-open range, where you have random.random() that always includes 1 but may 183 15:01.530 --> 15:09.120 never include 1, and you can multiply it and do whatever you like with it reliably knowing that. 184 15:09.120 --> 15:16.830 But because this one can vary depending on the rounding of the upper bound, then you may get the upper 185 15:16.830 --> 15:17.190 bound, 186 15:17.190 --> 15:17.850 you may not. 187 15:17.850 --> 15:21.270 So these are all really minute differences. 188 15:21.270 --> 15:29.370 I recommend to use random.random() if you can, and you understand how it works to extend the range. 189 15:30.690 --> 15:36.360 Now it's time to do some practice and see what you can actually do with random numbers, 190 15:36.360 --> 15:41.340 and I want you to create a heads or tail program. 191 15:41.340 --> 15:48.780 So the idea is that you should be able to comment out all the existing code if you have any, or delete 192 15:48.780 --> 15:49.860 it if you wish. 193 15:49.860 --> 15:59.430 And you're going to create a program that either prints out, "Heads", or it prints out "Tails", and whether 194 15:59.430 --> 16:07.170 if it prints out Heads or Tails will entirely depend on a random number that you generate. 195 16:07.170 --> 16:09.450 So think about how you can do that. 196 16:09.450 --> 16:11.520 Pause the video and give this a go. 197 16:17.210 --> 16:17.750 All right. 198 16:17.750 --> 16:19.880 So how do we do this? 199 16:19.910 --> 16:22.670 Well we need some conditions, right? 200 16:22.670 --> 16:26.540 We need to know that we can generate two random numbers; 201 16:26.540 --> 16:30.650 one will represent heads, and one will represent tails. 202 16:30.680 --> 16:38.480 Now if we want the numbers to occur at the same rate then we could for example, generate a random number 203 16:38.480 --> 16:41.000 that is either 1 or 0. 204 16:41.090 --> 16:42.710 So how can we do that? 205 16:42.710 --> 16:46.820 Well, we can use this randint() function that we learned earlier. 206 16:46.820 --> 16:51.620 So making sure that we've already got "import random" written up here. 207 16:51.620 --> 16:55.790 And don't worry if it goes gray, it does that because it's not being used. 208 16:55.790 --> 16:58.010 We can now use it. 209 16:58.010 --> 17:02.570 And you can see it turns it into normal syntax highlighting color. 210 17:02.780 --> 17:05.600 And then we can say random.randint(), 211 17:05.600 --> 17:09.710 and we want a random number between 0 and 1. 212 17:09.710 --> 17:11.390 So therefore we're going to get 0, 213 17:11.390 --> 17:12.860 or we're going to get 1, 214 17:12.860 --> 17:22.010 and we're going to set this to equal our random_heads_or_tails. 215 17:23.090 --> 17:26.060 Now you can of course call this whatever it is you wish, 216 17:26.060 --> 17:32.840 but essentially what we have here is a random number that is either 1 or 0. 217 17:32.840 --> 17:36.950 And we can verify this just by running this a few times. 218 17:36.950 --> 17:39.200 And you can see it's 1 or it's 0. 219 17:39.320 --> 17:46.550 So now instead of printing it out let's use an if statement and check if the random_heads_or_tails is 220 17:46.550 --> 17:47.900 equal to 0, 221 17:47.930 --> 17:52.420 well in that case, let's go ahead and print, "Heads", 222 17:52.420 --> 17:58.060 but otherwise the only other option is Tails. 223 17:58.060 --> 18:02.500 So let's go ahead and put print("Tails") into the else statement. 224 18:02.500 --> 18:07.810 So when it's 0 it's going to print "Heads" for any other situation which is only 1, 225 18:07.810 --> 18:09.430 then it's going to print "Tails". 226 18:09.430 --> 18:11.080 So now let's hit Run. 227 18:11.080 --> 18:15.760 You can see we have now a random coin toss. 228 18:15.760 --> 18:20.410 So because it's random you might see the same thing occur lots of times, 229 18:20.410 --> 18:26.530 but hopefully over a hundred times you will see it's roughly a 50/50 split. 230 18:27.520 --> 18:33.280 So I hope you had fun creating this program using your newfound knowledge. 231 18:33.280 --> 18:38.080 And once you're ready, head over to the next lesson and we'll continue the day's lessons.