WEBVTT 00:00.050 --> 00:02.900 Let's continue with our launch file and improve it. 00:02.900 --> 00:08.840 I will be using XML for the example, but still I will show you just in case, the Python syntax at 00:08.840 --> 00:09.980 the end of the video. 00:09.980 --> 00:15.380 So in the previous sections in this course you have seen that you can rename a node and you can remap 00:15.410 --> 00:17.660 topics and services at runtime. 00:17.660 --> 00:26.360 So for that you use the uh if you remember dash dash args and then dash R to rename, for example, 00:26.360 --> 00:34.490 a node like that, and then a topic to a new topic and the same thing for services. 00:34.490 --> 00:37.820 Well, this is something you can also do in a launch file. 00:37.820 --> 00:39.470 Let's see how you can do that. 00:39.470 --> 00:44.030 So first let's try to rename the node we want to rename. 00:44.030 --> 00:45.710 Well we can rename both nodes. 00:45.710 --> 00:47.300 In this case it's very easy. 00:47.300 --> 00:51.440 You have in this node tag you have pkg exec. 00:51.440 --> 00:59.690 And then you add another argument name and let's say my number publisher. 00:59.690 --> 01:00.560 And that's it. 01:00.560 --> 01:03.500 That's how you rename a node at runtime. 01:03.500 --> 01:06.590 When you start it with a launch file we can do the same here. 01:06.610 --> 01:09.760 name, which is going to be, uh. 01:09.760 --> 01:15.700 Well, let's just also use my number counter. 01:16.540 --> 01:16.900 Okay? 01:16.930 --> 01:31.030 Once I have done this, I will I will go back to my workspace and click on Build packages, select with 01:31.240 --> 01:33.550 my robot bring up. 01:34.480 --> 01:34.870 Great. 01:34.870 --> 01:35.950 And now I will. 01:35.980 --> 01:37.690 So I still have stuff here. 01:38.950 --> 01:42.730 I will source my environment. 01:43.000 --> 01:47.920 And I can do Ros to run my robot. 01:47.950 --> 01:50.980 Bring up with the number app. 01:51.040 --> 01:56.170 So number actually it's not rush to run you see it's Ros to launch. 01:56.170 --> 01:59.320 And I could see it because the auto completion didn't work. 01:59.350 --> 02:04.420 So Ros to launch my robot bring up. 02:04.420 --> 02:11.050 And that's going to be number app dot launch dot x m L. 02:13.260 --> 02:16.170 It is working and you can see already in the logs. 02:16.200 --> 02:18.120 So that's the executable name. 02:18.150 --> 02:18.360 Okay. 02:18.390 --> 02:21.690 Not to be confused with the node name. 02:21.690 --> 02:26.070 The node name is my number counter and my number publisher. 02:26.070 --> 02:35.610 We can see this with Ros2 node list and also with Actigraph you can see my number publisher my number 02:35.610 --> 02:36.120 counter. 02:36.120 --> 02:39.180 So we have correctly renamed the node. 02:39.210 --> 02:43.260 Now what if you want to remap a topic or a service that's going to be the same. 02:43.260 --> 02:46.080 What if I want to remap the number topic here? 02:47.070 --> 02:54.240 Well let's go back and to remap we will need to actually add another tag inside the node tag. 02:54.240 --> 02:59.370 So for now I have just closed the node tag like this so that it's just in one line. 02:59.400 --> 03:07.380 Now I'm going to remove this forward slash to open the node tag, and I'm going to close it like that. 03:09.000 --> 03:12.360 And now I can add more tags inside the node tag. 03:13.200 --> 03:15.630 So make sure you have just one angle bracket here. 03:15.660 --> 03:18.360 And here you have a forward slash. 03:19.360 --> 03:23.770 and I can use the remap tag and it's going to be very easy. 03:23.800 --> 03:30.700 You have a from argument and then a two argument and I'm going to close it like this. 03:31.600 --> 03:34.540 From is the previous name two is the new name. 03:34.540 --> 03:44.620 So the previous name we have for example number topic we want to rename to my number. 03:44.770 --> 03:49.510 And this way when we start the node is going to change the topic name. 03:49.510 --> 03:51.280 Or it's also working for services. 03:51.280 --> 03:54.910 It's the same from number to my number. 03:54.970 --> 03:59.500 Now if I do this of course it's not going to work for the number counter because the number counter 03:59.500 --> 04:02.350 is still subscribing to number. 04:02.350 --> 04:04.300 So I will do the same thing. 04:04.330 --> 04:12.790 I will open and close the node tag, and then I will add a remapping which is basically the same. 04:12.790 --> 04:17.110 So let's just take that one here and we also rename. 04:17.110 --> 04:20.260 So we remap the topic name in both nodes. 04:20.290 --> 04:23.230 All right let's save and let's build. 04:23.230 --> 04:24.840 Well actually I don't even need that one. 04:24.840 --> 04:27.360 I could I could directly build here. 04:27.390 --> 04:43.200 If I do ctrl c here, let's go to the workspace, click on build packages, select my robot bring up 04:44.880 --> 04:57.750 and then source install, setup bash and then Rose to launch my robot bring up still with the number 04:57.780 --> 05:01.740 app launch XML. 05:03.090 --> 05:05.580 So it is starting. 05:05.580 --> 05:09.390 We don't have any log for the topics, so what we can do? 05:09.420 --> 05:13.650 Well you could do a actually rose to topic list. 05:14.520 --> 05:16.500 You see now we have my number topic. 05:16.500 --> 05:19.920 And you can also verify that easily with arc graph. 05:20.640 --> 05:22.830 And you see now the topic is my number. 05:22.830 --> 05:26.850 So it has been remapped on that side and on that side. 05:26.850 --> 05:31.550 So the publisher and the subscriber are now using a different name for the topic. 05:31.550 --> 05:33.470 So you see, it's very powerful. 05:33.560 --> 05:34.070 Okay. 05:34.100 --> 05:40.370 From that launch file you can just change the name of the nodes, change the topic name, the service 05:40.370 --> 05:40.880 name. 05:40.910 --> 05:41.240 Okay. 05:41.270 --> 05:43.700 All that from one file. 05:43.700 --> 05:47.030 And you see we only have eight lines of code here. 05:47.030 --> 05:51.590 To start, two nodes with a different name and a different topic name. 05:51.590 --> 05:55.850 And let's have a quick look at the Python launch file for the same thing. 05:55.850 --> 06:00.020 So this is the previous one and I have had it in my nodes you see. 06:00.050 --> 06:02.870 So this config is still not that complicated. 06:03.140 --> 06:05.450 Uh you have a name argument. 06:06.020 --> 06:07.640 You can change the name of the node. 06:07.640 --> 06:08.840 So we change it here. 06:08.840 --> 06:10.370 We change it there as well. 06:10.370 --> 06:16.970 And then for Remappings you have a remappings argument which is actually a list of tuples. 06:16.970 --> 06:22.220 So you need to provide one tuple for each remapping that you want. 06:22.250 --> 06:25.430 And you see with the previous name and the current name. 06:25.520 --> 06:26.000 All right. 06:26.000 --> 06:32.540 And even if I could save on spaces, you see now we have 24 lines and eight lines here. 06:32.540 --> 06:32.990 But what. 06:33.020 --> 06:37.310 So here's the Python way to do renamings and remappings.