WEBVTT 00:00.050 --> 00:04.100 To create a raster node, you first need a package. 00:04.130 --> 00:08.360 Packages will allow you to separate your code into reusable blocks. 00:08.390 --> 00:11.060 Each package is an independent unit. 00:11.060 --> 00:16.850 For example, in one application you could have one package that will handle a camera, another package 00:16.850 --> 00:21.980 that will run the wheels of your robot, and yet another one that will handle motion planning for the 00:21.980 --> 00:23.750 robot in the environment. 00:23.750 --> 00:29.120 So we will first create a simple Python package here, and you will learn more about packages and best 00:29.120 --> 00:31.220 practices all along this course. 00:31.250 --> 00:37.220 Note that in Ros2, Python packages and Cplusplus packages have a complete different architecture. 00:38.330 --> 00:41.660 So where will we create our Python package? 00:41.660 --> 00:45.110 Well, that's going to be inside our Ros2 workspace. 00:45.110 --> 00:50.240 So you go inside the Ros2 workspace and you go also in the source folder okay. 00:50.270 --> 00:54.620 Make sure that you create all the files inside this src folder. 00:54.650 --> 00:55.550 It's very important. 00:55.550 --> 00:57.410 So now this is empty of course. 00:57.440 --> 01:01.500 And to create a package we are going to use the Ros two command line. 01:01.740 --> 01:01.890 Okay. 01:01.920 --> 01:03.750 I'm going to come back to this a lot. 01:03.780 --> 01:07.890 During this course we're going to explore a lot of different commands you can use with Ros two. 01:07.920 --> 01:10.440 So Ros two and then space. 01:10.440 --> 01:16.290 And we can use the PKG command to create a package with the create keyword. 01:16.290 --> 01:18.210 So Ros two pkg create. 01:18.210 --> 01:20.670 Then we need to give a name for the package. 01:20.670 --> 01:26.640 So for example if your package would be monitoring a temperature sensor it could be a temperature sensor 01:26.640 --> 01:27.330 package. 01:27.330 --> 01:32.100 Here I'm just going to name it my pi pkg. 01:32.100 --> 01:33.690 So my Python package okay. 01:33.720 --> 01:39.690 As a first example for this course, make sure that you use underscores to separate words. 01:39.690 --> 01:44.610 If you want inside the name of the package after the name, you will need to precise. 01:44.610 --> 01:48.540 If the package is a Python package or a C plus plus package for example. 01:48.540 --> 01:52.800 So you can do this with build type okay. 01:52.830 --> 01:53.250 Like this. 01:53.250 --> 01:55.770 So dash dash build dash type. 01:55.770 --> 01:57.180 And you can use Autocompletion. 01:57.180 --> 01:58.380 As you can see it should work. 01:58.410 --> 02:00.300 And then you provide the build type. 02:00.300 --> 02:04.260 And we're going to write element underscore Python. 02:05.040 --> 02:06.420 So what is element. 02:06.450 --> 02:08.700 Element is the build system. 02:08.880 --> 02:10.920 So we have call con that is the build tool. 02:10.920 --> 02:12.600 And element is the build system. 02:12.600 --> 02:15.960 You're going to see quite a few times in different files. 02:15.960 --> 02:21.240 And to say that the package is a Python package you need to write element underscore Python. 02:21.240 --> 02:24.030 And that's pretty much it for the package. 02:24.030 --> 02:26.940 Now what you can do is you can also add dependencies. 02:26.940 --> 02:34.110 So dependencies like this which are basically other packages that this package will depend on. 02:34.110 --> 02:38.640 So of course we will be able to add all the dependencies later directly inside the package, but you 02:38.640 --> 02:42.390 can also provide them already from the start. 02:42.390 --> 02:47.040 So here I'm going to add one rcl py and rcl. 02:47.040 --> 02:49.800 Py is the Python library. 02:49.800 --> 02:53.700 So you can write Python code to use the ros2 features. 02:53.700 --> 03:00.340 So of course if we're going to write Python nodes We want to use the Python ros2 library. 03:00.340 --> 03:03.340 So now that we have all that let's press enter. 03:03.370 --> 03:05.470 That's going to create a package. 03:05.470 --> 03:12.970 You can see we have lots of logs with creating folders, creating files etc. and we also have. 03:12.970 --> 03:14.770 So you might have this warning. 03:14.770 --> 03:17.440 If you have this warning it's really not important. 03:17.440 --> 03:20.620 It's just to say that you don't have a license file. 03:20.620 --> 03:22.930 So having a license file is going to be important. 03:22.930 --> 03:27.880 If you want to publish your code with an open source license somewhere on GitHub, for example, if 03:27.880 --> 03:29.830 you want other people to use, etc.. 03:29.830 --> 03:34.570 But for now, for learning and for most projects you will do, you don't really need to publish your 03:34.570 --> 03:37.210 code online, so we don't really need a license. 03:37.210 --> 03:40.300 So you can just ignore completely this warning. 03:40.300 --> 03:42.010 So let's do a clear. 03:42.130 --> 03:47.980 And now if I do ls you see I have my pi pkg. 03:47.980 --> 03:50.050 So that's my new package. 03:50.050 --> 03:51.910 And let's see what we have inside. 03:51.940 --> 03:57.860 To do this I'm going to open Visual Studio Code and to open Visual Studio Code, I recommend that you 03:57.860 --> 03:59.600 always do the following. 03:59.600 --> 04:07.160 So first you navigate inside your source folder here of the roster workspace, not anywhere else. 04:07.160 --> 04:08.480 And then you do code. 04:08.480 --> 04:16.700 That's the command to launch VSCode and then dot to say you want to open VSCode from the source folder. 04:16.700 --> 04:22.310 I recommend you do that because if you open VSCode from different parts every time, that might be a 04:22.310 --> 04:24.830 problem, especially for Autocompletion. 04:24.860 --> 04:31.880 Okay, because VSCode might not find the includes and the imports, etc. so better to open it from the 04:31.880 --> 04:32.810 source folder. 04:32.810 --> 04:33.770 That's what I'm doing here. 04:33.800 --> 04:36.020 Code space dot. 04:40.850 --> 04:41.390 Okay. 04:41.390 --> 04:44.750 And you can see that I have my source folder. 04:44.750 --> 04:47.660 So we have a new VSCode folder. 04:47.660 --> 04:49.160 We're going to come back to this later. 04:49.160 --> 04:51.620 That's just stuff for VSCode. 04:51.620 --> 04:56.250 And then we have well this package that we have created my Python package. 04:56.250 --> 04:57.570 And what do we have inside? 04:57.570 --> 04:59.190 You see, we have quite a lot of stuff. 04:59.190 --> 05:05.010 First of all, you will find another folder that has exactly the same name as the package. 05:05.010 --> 05:09.630 So if your package was named ABC, that folder would be named ABC. 05:09.720 --> 05:13.110 And inside you have an empty init.py. 05:13.140 --> 05:18.240 Okay, so this folder here is where you will write your Python code. 05:18.240 --> 05:19.950 Then we have a resource folder. 05:19.980 --> 05:22.140 Don't really need to worry about that. 05:22.440 --> 05:25.110 A test folder with test stuff. 05:25.110 --> 05:27.720 But also we don't need to worry about that right now. 05:27.720 --> 05:29.490 And then we have three more files. 05:29.490 --> 05:31.560 So we have a package dot XML. 05:31.560 --> 05:36.540 This file is quite important and it's mandatory for any ros2 package okay. 05:36.540 --> 05:37.890 And what do you have inside. 05:37.920 --> 05:43.440 Well as you can see we have stuff like name version description. 05:43.440 --> 05:45.510 You can put a maintenance email or license. 05:45.510 --> 05:50.940 So if you're going to publish your code somewhere on GitHub for example, you will need to fill this 05:50.940 --> 05:52.680 with accurate information. 05:52.700 --> 05:55.580 Then you see we have a depend tag with RCL. 05:55.610 --> 06:03.110 Py so that's because we have provided the CLP dependency in the command line when we created the package. 06:03.110 --> 06:05.240 Now if you want to add more dependencies. 06:05.240 --> 06:11.690 So if this package here that you've created depends on more other packages, you will need to add other 06:11.690 --> 06:12.620 dependency tag. 06:12.620 --> 06:15.500 So one tag per line we have more stuff here. 06:15.500 --> 06:19.760 And in the end you also see the build type here amount Python. 06:19.790 --> 06:20.060 All right. 06:20.090 --> 06:22.790 So that's about it for the package dot XML for now. 06:23.060 --> 06:29.690 And then you have a setup.cfg and setup.py that's going to be used when we want to install the nodes. 06:29.690 --> 06:32.960 We're going to come back to that when we create a node okay. 06:32.990 --> 06:37.190 So that's what you can find in a Python package. 06:37.190 --> 06:38.930 Now let's go back to the terminal. 06:38.930 --> 06:41.510 And we can build this Python package. 06:41.540 --> 06:44.090 Even if it has no node we can build it. 06:44.090 --> 06:48.050 So let's go back to Ros2 workspace okay. 06:48.080 --> 06:51.050 You always go back to this Ros2 workspace. 06:51.050 --> 06:55.750 You don't build inside the source folder you build inside the Ros2 workspace. 06:55.750 --> 07:04.780 Once we are here, we can do a call on build and you can see we have starting my Python package and 07:04.780 --> 07:06.790 then finished my Python package. 07:06.790 --> 07:08.770 So that package has been built. 07:08.770 --> 07:11.080 And I'm just going to show you one option here. 07:11.080 --> 07:16.660 So you can use call build with packages select and you can press tab. 07:16.660 --> 07:23.110 Here you should have the Autocompletion and then my Python package with Autocompletion okay. 07:23.140 --> 07:28.420 So if I do this well you will see the result is going to be the same because we only have one package. 07:28.420 --> 07:31.480 But that option is quite convenient to use. 07:31.480 --> 07:35.410 It's only going to build the packages that you actually select. 07:35.410 --> 07:38.710 So the packages that you write after this option. 07:38.740 --> 07:39.010 All right. 07:39.040 --> 07:43.720 So if you just want to build that package, if you have let's say 12 packages and you just want to build 07:43.720 --> 07:46.660 that one, you can use this option as well. 07:46.690 --> 07:47.080 All right. 07:47.080 --> 07:51.130 And now your Python package is ready to host a Python node.