WEBVTT 00:00.050 --> 00:05.450 In the previous lesson, you have discovered what variables were, and so far you've only used variables 00:05.450 --> 00:07.580 to store integer numbers. 00:07.580 --> 00:10.280 So round numbers as you can see, like this. 00:10.280 --> 00:13.280 But in fact there are many more types you can use. 00:13.280 --> 00:20.030 Let's discover the most important ones now that you will basically need in all your future programs. 00:20.030 --> 00:23.120 So I'm going to remove all of that. 00:23.570 --> 00:28.070 You can save it and reuse later to follow the videos again if you want. 00:28.100 --> 00:31.220 And we're going to start to create a variable with. 00:31.250 --> 00:32.570 So let's name it a. 00:32.600 --> 00:37.880 So just a quick note I just told you about using meaningful names for variables okay. 00:37.910 --> 00:39.290 We're going to do that in a minute. 00:39.290 --> 00:41.060 For now I just use a. 00:41.090 --> 00:44.300 So we just focus on the data types for variables. 00:44.300 --> 00:46.730 And then later on we're going to use more meaningful names. 00:46.730 --> 00:51.050 So the first thing you've seen is for example we can do a is equal to five. 00:51.080 --> 00:56.510 That is a integer number I can print a okay. 00:56.510 --> 01:01.250 So I can run that and it's going to print five. 01:01.340 --> 01:04.750 And somehow well I'm not sure exactly why I have this. 01:04.780 --> 01:07.690 Well, if you have the same, you can just close. 01:07.690 --> 01:12.940 It's probably a problem with my keyboard, but that's not really a problem. 01:12.940 --> 01:14.200 Just start again. 01:14.200 --> 01:18.010 So this number, this round number is called the integer. 01:18.040 --> 01:19.150 It can be five. 01:19.180 --> 01:20.500 It can be a big number. 01:20.500 --> 01:21.760 It can be a small number. 01:21.760 --> 01:22.480 It can be zero. 01:22.480 --> 01:24.760 It can also be a negative number okay. 01:24.790 --> 01:27.820 So for example minus ten that's going to work as well. 01:27.820 --> 01:29.380 That's an integer number. 01:29.380 --> 01:33.490 Then the second kind of data type is float number. 01:33.490 --> 01:37.660 So float number is simply a number but with a decimal with a comma. 01:37.660 --> 01:44.590 So for example 3.14 I can run that okay 3.14. 01:44.620 --> 01:46.390 And you're going to use a point okay. 01:46.420 --> 01:49.690 So 3.14 it can also be a negative number. 01:49.720 --> 01:54.130 Well let's run this -3.14 okay. 01:54.160 --> 01:57.070 So you have two ways of representing a number in Python. 01:57.070 --> 02:02.110 Basically you have the round numbers which are integers and the float numbers okay. 02:02.140 --> 02:05.200 For decimal numbers then we have strings. 02:05.200 --> 02:07.940 So we have actually used strings before. 02:07.970 --> 02:14.150 I just need to put as I'm going to remove that and I just need to put a double quotes twice okay. 02:14.180 --> 02:16.550 And then I can write any piece of text. 02:16.550 --> 02:22.250 So any piece of text you can see, I can write anything I want. 02:22.280 --> 02:23.990 And that's going to be printed here. 02:24.020 --> 02:24.260 Okay. 02:24.290 --> 02:31.460 I print a which is this chain of characters also called a string. 02:31.460 --> 02:35.870 And the fourth type that we are going to see here is called Boolean. 02:35.870 --> 02:37.490 So what is a Boolean? 02:37.490 --> 02:41.180 In a boolean you can only put two different values. 02:41.180 --> 02:43.400 That's going to be true or false. 02:43.400 --> 02:45.320 And there are special keywords for that okay. 02:45.350 --> 02:49.250 You can see true here we have a syntax highlighting okay. 02:49.250 --> 02:51.530 It's it's purple and bold. 02:51.530 --> 02:55.040 And I have also false okay. 02:55.040 --> 02:58.640 So if I run this you can see now we have false. 02:58.640 --> 03:03.560 And this kind of value is quite useful if you want to check for example if a push button is pressed 03:03.590 --> 03:05.420 is it true or is it false. 03:05.450 --> 03:07.310 And you can use a boolean value okay. 03:07.340 --> 03:09.890 And for this you have the two keywords true and false. 03:09.920 --> 03:15.220 Note that it's very important to write them exactly like this with a f uppercase. 03:15.250 --> 03:18.970 If I write false like this, look at what's going to happen. 03:18.970 --> 03:22.510 We have an error because false is not defined here. 03:22.510 --> 03:26.710 It thinks that false is going to be some variables that we have defined before okay. 03:26.740 --> 03:33.550 You need to use the f uppercase okay false keyword because this is a recognized keyword. 03:33.610 --> 03:38.080 And if I put true then it's going to be true okay. 03:38.110 --> 03:42.250 So we have integers float numbers strings and booleans. 03:42.250 --> 03:43.840 For now we're going to keep using those. 03:43.840 --> 03:47.950 And you can really do a lot of things already with those four data types. 03:48.250 --> 03:54.100 And if you are not sure about the type that you have set inside a variable, you can use the function. 03:54.100 --> 03:59.080 So there is another function for now you know print but there is another function is called type. 03:59.710 --> 04:03.130 You can see also with syntax highlighting here. 04:03.130 --> 04:08.410 So I'm going to write type open and close parentheses and then put a variable inside. 04:08.440 --> 04:11.020 And let's press play here. 04:11.020 --> 04:12.670 And you can see class. 04:12.670 --> 04:14.440 So don't worry about the class here. 04:14.450 --> 04:16.550 But you can see bull that's a boolean. 04:16.550 --> 04:22.760 And what happened here is that you can see that we have a functionality inside another functionality. 04:22.760 --> 04:24.890 So that's perfectly valid. 04:24.890 --> 04:29.930 What's going to happen is that first this is going to be evaluated. 04:30.380 --> 04:37.880 So it's going to fetch a and then get the type of a and then print the result of that. 04:37.880 --> 04:39.260 So print the type of a. 04:39.290 --> 04:41.060 So here you have bull. 04:41.780 --> 04:47.660 Um if I put for example three then the type of three is going to be int okay. 04:47.690 --> 04:52.430 If I put 3.14 this is going to be float. 04:52.520 --> 05:00.980 But now for example if I put 3.0 just 3.0 instead of three, you can see that this is also considered 05:00.980 --> 05:02.150 as a float. 05:02.180 --> 05:02.660 Okay. 05:02.690 --> 05:06.380 So there is a difference between 3 and 3.0. 05:07.190 --> 05:08.210 As you can see here. 05:08.210 --> 05:13.760 And now if I put quotes like this, if we print a we're going to see three. 05:13.760 --> 05:17.210 But the type as you can see this is a string. 05:17.210 --> 05:19.090 And once again I have this error. 05:19.450 --> 05:23.050 So if you put quotes, whatever inside is going to be a string. 05:23.080 --> 05:23.290 Okay. 05:23.320 --> 05:25.060 Even if it's a number okay. 05:25.090 --> 05:29.980 Even if you type true, you can see that's still a string. 05:29.980 --> 05:36.220 So just in case, if you are doubting about the type that is inside a variable, you can use the type 05:36.220 --> 05:36.340 here. 05:36.340 --> 05:42.100 And you can print it to make sure that you are using the correct type, because this could lead to some 05:42.100 --> 05:43.390 errors in the future. 05:43.390 --> 05:45.670 So let's come back to integer number. 05:45.670 --> 05:47.770 Here we have a int. 05:47.770 --> 05:54.580 And as you can see the type of a variable is dynamically set when you create the variable okay. 05:54.610 --> 05:59.950 With languages like C, C plus plus and Java for example, you have to specify the type. 05:59.950 --> 06:05.020 Also, when you first use the variable you have to do that manually, not in Python. 06:05.020 --> 06:11.350 So it means that you can put whatever you want inside A and A is going to become the type of that value 06:11.380 --> 06:12.010 here. 06:12.010 --> 06:17.530 And it means also that you could change the variable's type anytime in your program. 06:17.530 --> 06:20.080 So now a is an integer. 06:20.080 --> 06:27.570 But I could say then that A is hello and let's print the type of A again. 06:28.800 --> 06:30.270 Let's run. 06:31.020 --> 06:35.250 And you can see a was first an integer and now A is a string. 06:35.250 --> 06:37.560 So this is possible in Python. 06:37.590 --> 06:44.130 However this practice is strongly discouraged even if you can theoretically do it in practice. 06:44.160 --> 06:48.450 This is a good way to mess up your programs and get a lot of errors. 06:48.450 --> 06:54.870 So when you have set a variable, you can change it to any value after that, but stick to values that 06:54.870 --> 06:57.570 are of the same type as the original one. 06:57.600 --> 07:03.060 One advice to avoid making mistakes with types is simply to use meaningful names for your variables. 07:03.060 --> 07:09.930 So for example, let's remove that and let's use Wi-Fi underscore name okay. 07:09.960 --> 07:14.310 And put the Wi-Fi name so your Wi-Fi. 07:15.810 --> 07:17.370 A variable named Wi-Fi name. 07:17.370 --> 07:19.890 Well it's probably going to contain a string. 07:19.890 --> 07:24.510 So you will not modify it later for an integer or a boolean or a float. 07:24.520 --> 07:28.240 So here's a meaningful name, for example, for a string. 07:28.270 --> 07:32.350 Then let's say you are going to store a temperature. 07:33.070 --> 07:34.210 So temperature. 07:34.210 --> 07:38.980 Well we use the integer before but you could use a float number. 07:38.980 --> 07:41.140 So for example 20.5. 07:41.170 --> 07:43.600 Then for example you want to create a user age. 07:43.600 --> 07:45.610 So you want to store the user age. 07:45.640 --> 07:48.070 User age is going to be an integer number. 07:48.070 --> 07:50.140 So it's no mistake with this. 07:50.140 --> 07:55.780 And finally let's say you want to check if the camera that you have plugged to the Raspberry Pi is still 07:55.780 --> 07:56.290 alive. 07:56.290 --> 07:58.540 So let's say alive means connected here. 07:58.540 --> 08:05.020 So you can create a variable name is alive is equal to true okay. 08:05.020 --> 08:07.300 And that's going to be a boolean true or false. 08:07.330 --> 08:07.720 All right. 08:07.720 --> 08:12.460 So as best practice I really encourage you to think about a variable name. 08:12.460 --> 08:16.750 Anytime you're going to create a variable and give a name that is meaningful. 08:16.780 --> 08:17.290 All right. 08:17.290 --> 08:23.560 To recap on this lesson, you can use different types of variables depending on the value you want to 08:23.590 --> 08:24.010 store. 08:24.010 --> 08:28.870 For example, integers, float numbers, strings, and booleans.