WEBVTT 1 00:00:00.630 --> 00:00:02.750 Hi guys and welcome back. In this video, 2 00:00:02.750 --> 00:00:05.663 we're going to talk about relative imports in Python. 3 00:00:05.663 --> 00:00:07.600 This is something that's really confusing 4 00:00:07.600 --> 00:00:10.200 for new Python beginners, and to be honest, 5 00:00:10.200 --> 00:00:11.880 it's a bit weird. 6 00:00:11.880 --> 00:00:14.260 And you're not going to be using them very much at all 7 00:00:14.260 --> 00:00:15.580 but I just wanted to talk about them 8 00:00:15.580 --> 00:00:17.680 so that you all use them precisely 9 00:00:17.680 --> 00:00:19.330 because they work very differently 10 00:00:19.330 --> 00:00:21.540 than what you might expect. 11 00:00:21.540 --> 00:00:24.750 What I've got here is four files now. 12 00:00:24.750 --> 00:00:29.140 I've got code, and mymodule in the same folder. 13 00:00:29.140 --> 00:00:34.140 Then we've got our libs folder that contains mylib. 14 00:00:34.790 --> 00:00:37.150 And then we've got our operations folder 15 00:00:37.150 --> 00:00:39.540 that contains operator. 16 00:00:39.540 --> 00:00:44.493 So code imports mymodule, mymodule imports libs.mylib, 17 00:00:45.470 --> 00:00:49.950 and mylib imports libs.operations.operator. 18 00:00:49.950 --> 00:00:52.290 And each one prints out their name. 19 00:00:52.290 --> 00:00:57.290 So if we press play right now, what you get back is-- 20 00:00:57.680 --> 00:00:59.950 Well first of all, something important to note is that-- 21 00:00:59.950 --> 00:01:01.170 I may not have mentioned it in the last video, 22 00:01:01.170 --> 00:01:04.010 is that when you run the import, 23 00:01:04.010 --> 00:01:06.130 that immediately jumps into the next file 24 00:01:06.130 --> 00:01:07.180 and starts running it. 25 00:01:07.180 --> 00:01:10.980 So of course, code.py imports mymodule 26 00:01:10.980 --> 00:01:12.820 so that stops code.py from running 27 00:01:12.820 --> 00:01:16.470 and Python jumps to mymodule. This imports mylib. 28 00:01:16.470 --> 00:01:18.440 So this stops running and jumps to mylib. 29 00:01:18.440 --> 00:01:20.250 This imports operator so that stops running 30 00:01:20.250 --> 00:01:23.420 and jumps to operator, and that prints. 31 00:01:23.420 --> 00:01:27.100 Then we go back to mylib and then we print, 32 00:01:27.100 --> 00:01:29.820 then we go back to mymodule, then we print, 33 00:01:29.820 --> 00:01:31.600 then we go back to code and then we print. 34 00:01:31.600 --> 00:01:33.530 So that's why the order here is reversed 35 00:01:33.530 --> 00:01:35.730 from the order in which the files are running. 36 00:01:35.730 --> 00:01:38.250 Code is running first but that prints out last 37 00:01:38.250 --> 00:01:42.200 because of that tree of imports that's going on. 38 00:01:42.200 --> 00:01:44.530 So this is not relative imports. 39 00:01:44.530 --> 00:01:48.600 These are just absolute imports where you have to define 40 00:01:48.600 --> 00:01:50.350 the path that you're importing from. 41 00:01:50.350 --> 00:01:55.180 So here and the path is libs.operations.operator 42 00:01:55.180 --> 00:01:58.640 and we're doing from libs.operations import operator, 43 00:01:58.640 --> 00:02:02.980 or you could do import libs.opererations.operator 44 00:02:02.980 --> 00:02:04.290 if you preferred, although then 45 00:02:04.290 --> 00:02:06.020 you would have to access things like 46 00:02:06.020 --> 00:02:08.980 libs.operations.operator.divide. 47 00:02:08.980 --> 00:02:13.270 If a divide function was defined inside that file, 48 00:02:13.270 --> 00:02:14.103 which it's not. 49 00:02:14.103 --> 00:02:15.910 At the moment, nothing's defined inside these files. 50 00:02:15.910 --> 00:02:17.990 They're just printing out their names. 51 00:02:17.990 --> 00:02:20.870 So that is absolute imports. 52 00:02:20.870 --> 00:02:23.250 Let's talk about relative imports. 53 00:02:23.250 --> 00:02:27.330 A relative import is one that can import 54 00:02:27.330 --> 00:02:31.900 from the current folder that the file is in. 55 00:02:31.900 --> 00:02:36.730 But it cannot import unless there is a folder name 56 00:02:36.730 --> 00:02:39.950 in the import path, in the module path. 57 00:02:39.950 --> 00:02:42.784 So, here's what that means. 58 00:02:42.784 --> 00:02:46.160 Libs.mylib when it prints out the name 59 00:02:46.160 --> 00:02:49.190 you can see that there is a folder inside the import path 60 00:02:49.190 --> 00:02:51.530 that is separated from other things in the path 61 00:02:51.530 --> 00:02:53.390 by a full stop, a period. 62 00:02:53.390 --> 00:02:55.250 So here you've got the libs folder 63 00:02:55.250 --> 00:02:57.370 and inside it you've got the mylib file. 64 00:02:57.370 --> 00:02:58.550 You can tell this is the file 65 00:02:58.550 --> 00:03:02.620 because it's the last thing in the import. 66 00:03:02.620 --> 00:03:05.890 Similarly, the operator.py has the file operator, 67 00:03:05.890 --> 00:03:07.180 that's where we're importing from 68 00:03:07.180 --> 00:03:10.360 and two folders, operations and libs. 69 00:03:10.360 --> 00:03:13.610 So, from these two you can do relative imports 70 00:03:13.610 --> 00:03:15.200 because there is a folder. 71 00:03:15.200 --> 00:03:17.270 From these two you cannot do relative imports 72 00:03:17.270 --> 00:03:19.080 because there's no folder. 73 00:03:19.080 --> 00:03:20.590 So let me show you what happens 74 00:03:20.590 --> 00:03:22.490 if you try to do a relative import 75 00:03:22.490 --> 00:03:24.640 and you don't have a folder. 76 00:03:24.640 --> 00:03:26.470 In order to do a relative import 77 00:03:26.470 --> 00:03:28.680 you need to use the from syntax. 78 00:03:28.680 --> 00:03:33.420 So you can do from .mymodule import divide let's say 79 00:03:33.420 --> 00:03:36.173 and I'm going to just add a divide function here. 80 00:03:38.780 --> 00:03:40.660 So (mumbles) divide function there it doesn't do anything 81 00:03:40.660 --> 00:03:44.220 and we're gonna try to import it from .mymodule. 82 00:03:44.220 --> 00:03:47.080 So what that means is from the current folder 83 00:03:47.080 --> 00:03:51.090 look at the mymodule file and import the divide function. 84 00:03:51.090 --> 00:03:56.090 So that makes sense because mymodule is in the same folder 85 00:03:56.720 --> 00:04:00.200 as code.py. You can see down here they're in the same folder 86 00:04:00.200 --> 00:04:02.160 so they should be fine. 87 00:04:02.160 --> 00:04:04.880 But when you try to do that, 88 00:04:04.880 --> 00:04:09.880 what it does is it tries to import from __main.mymodule. 89 00:04:12.230 --> 00:04:16.270 So as you can see because the name of this file was __main 90 00:04:16.270 --> 00:04:18.270 and it doesn't have a folder, 91 00:04:18.270 --> 00:04:21.890 it tries to import from the current place it's in 92 00:04:21.890 --> 00:04:24.460 and Python won't let you do that. 93 00:04:24.460 --> 00:04:28.120 If you are importing from the file you run, 94 00:04:28.120 --> 00:04:31.300 you can't use relative imports. 95 00:04:31.300 --> 00:04:36.300 Going into mymodule.py you could do from .libs import mylib 96 00:04:37.090 --> 00:04:39.710 and what that's going to do is it's going to try to access 97 00:04:39.710 --> 00:04:43.010 the libs folder inside the current folder, 98 00:04:43.010 --> 00:04:44.980 that's what the dot means. 99 00:04:44.980 --> 00:04:47.523 But again, if you try to run this code, 100 00:04:48.570 --> 00:04:51.370 you're going to get that you attempted a relative import 101 00:04:51.370 --> 00:04:54.830 with no known parent package. 102 00:04:54.830 --> 00:04:58.770 Again, mymodule has no information about the folder it's in 103 00:04:58.770 --> 00:05:01.713 so Python can't do a relative import from it. 104 00:05:02.890 --> 00:05:05.760 I'll show you again these paths here, 105 00:05:05.760 --> 00:05:07.270 because what you've got-- 106 00:05:07.270 --> 00:05:10.093 Oh, sorry I'll run code.py so it's the same as before. 107 00:05:11.040 --> 00:05:15.510 What you've got is that mymodule and main 108 00:05:15.510 --> 00:05:17.750 are at the top level. 109 00:05:17.750 --> 00:05:19.580 When you're trying to do a relative import, 110 00:05:19.580 --> 00:05:22.320 what Python's going to do is it's going to remove the file 111 00:05:22.320 --> 00:05:23.870 and it's just going to try to append 112 00:05:23.870 --> 00:05:27.670 whatever you import from into the rest of the import path. 113 00:05:27.670 --> 00:05:31.900 So if we go to mylib and then we do from .operations 114 00:05:31.900 --> 00:05:35.387 import operator, what that's gonna do is it's gonna say, 115 00:05:35.387 --> 00:05:40.120 "Okay, mylib, you are inside libs.mylib." 116 00:05:40.120 --> 00:05:43.140 So, because you're trying to do a relative import, 117 00:05:43.140 --> 00:05:45.140 we're going to remove the file 118 00:05:45.140 --> 00:05:48.090 and we're gonna try to put operations at the end 119 00:05:48.090 --> 00:05:49.070 and import from there. 120 00:05:49.070 --> 00:05:52.180 So here it'll work because it'll do libs.operations 121 00:05:52.180 --> 00:05:54.500 and then it'll import operator from that. 122 00:05:54.500 --> 00:05:57.130 So if I run code.py again, 123 00:05:57.130 --> 00:05:59.030 you can see that it all works fine. 124 00:05:59.030 --> 00:06:01.050 There's no errors whatsoever. 125 00:06:01.050 --> 00:06:05.880 However, if by any reason you want to run your mylib file, 126 00:06:05.880 --> 00:06:08.950 for example to debug it or run some code inside it, 127 00:06:08.950 --> 00:06:11.010 make sure it works or something like that, 128 00:06:11.010 --> 00:06:13.730 you won't be able to because, of course, 129 00:06:13.730 --> 00:06:16.540 this now becomes main, if you run it, 130 00:06:16.540 --> 00:06:19.440 and then you can't use relative imports from inside it. 131 00:06:19.440 --> 00:06:22.180 So, if you are going to use relative imports, 132 00:06:22.180 --> 00:06:25.700 you always have to run the same file at the top level, 133 00:06:25.700 --> 00:06:28.093 otherwise you may encounter some issues. 134 00:06:28.950 --> 00:06:30.203 Going into operator.py, 135 00:06:31.110 --> 00:06:35.660 you can actually do from ..mylib import star, let's say, 136 00:06:35.660 --> 00:06:36.900 and what this does in Python 137 00:06:36.900 --> 00:06:39.640 is it accesses the parent folder. 138 00:06:39.640 --> 00:06:43.800 So again if operator is inside libs.operations, 139 00:06:43.800 --> 00:06:47.120 dot dot is going to try to remove the operation 140 00:06:48.111 --> 00:06:50.120 and go direct to the previous one. 141 00:06:50.120 --> 00:06:54.130 So it'll try to do libs.mylib. That's what the dot dot means 142 00:06:54.130 --> 00:06:57.240 it just skips the parent folder and goes up to the next one. 143 00:06:57.240 --> 00:06:59.810 So, of course in order to do that, 144 00:06:59.810 --> 00:07:02.010 you need to be at least two levels deep. 145 00:07:02.010 --> 00:07:04.950 Otherwise if you try to do that for example from libs.mylib, 146 00:07:04.950 --> 00:07:07.760 you're going to try to skip libs and go to the previous one, 147 00:07:07.760 --> 00:07:10.700 but there is no previous one, so you'll find that error. 148 00:07:10.700 --> 00:07:12.180 So, again in order to do this, 149 00:07:12.180 --> 00:07:14.990 you need to do something like that, 150 00:07:14.990 --> 00:07:17.493 and that you can see works totally fine. 151 00:07:19.040 --> 00:07:22.920 Let's go back to why we didn't print anything else out 152 00:07:22.920 --> 00:07:25.010 when we ran this code because as you can see 153 00:07:25.010 --> 00:07:27.650 this output is exactly identical to the one we had before, 154 00:07:27.650 --> 00:07:30.000 so it seems that this did nothing. 155 00:07:30.000 --> 00:07:32.400 But really what's happened is Python has realised 156 00:07:32.400 --> 00:07:37.010 that libs.mylib had already been imported by mymodule 157 00:07:37.010 --> 00:07:39.520 before we imported operator. 158 00:07:39.520 --> 00:07:41.560 So, it didn't try to import it again. 159 00:07:41.560 --> 00:07:45.490 This just reuses the import that's already on six modules. 160 00:07:45.490 --> 00:07:47.360 So that's why we didn't see any more output. 161 00:07:47.360 --> 00:07:50.480 mylib.py didn't run again when we tried to import this. 162 00:07:50.480 --> 00:07:53.020 It was already in dot modules. 163 00:07:53.020 --> 00:07:55.190 I also wanted to say that at any point in time 164 00:07:55.190 --> 00:07:58.820 if you wanted to import say operator.py from mymodule, 165 00:07:58.820 --> 00:08:01.123 you can do import libs.operations.operator, 166 00:08:02.160 --> 00:08:06.450 or of course, from libs.operations import operator. 167 00:08:06.450 --> 00:08:08.400 You can do that as well. 168 00:08:08.400 --> 00:08:10.620 By the way, this just means import everything 169 00:08:10.620 --> 00:08:13.270 that is inside this path here. 170 00:08:13.270 --> 00:08:15.300 So if there were multiple functions, 171 00:08:15.300 --> 00:08:16.470 you would import them all. 172 00:08:16.470 --> 00:08:18.720 If there's multiple variables defined in there, 173 00:08:18.720 --> 00:08:21.320 you would also import them, and so on. 174 00:08:21.320 --> 00:08:22.860 All right that's everything for this video. 175 00:08:22.860 --> 00:08:25.470 Thank you for joining me. I know this stuff is confusing, 176 00:08:25.470 --> 00:08:29.410 but my advice is to not use relative imports in Python. 177 00:08:29.410 --> 00:08:32.260 They are difficult to understand, they're confusing, 178 00:08:32.260 --> 00:08:35.220 they only work if you always run the same files, 179 00:08:35.220 --> 00:08:37.950 and they won't work if you try to run other files 180 00:08:37.950 --> 00:08:39.830 such as the ones that use relative imports 181 00:08:39.830 --> 00:08:42.290 for debugging or to try things out. 182 00:08:42.290 --> 00:08:45.100 So, don't use them. Use absolute imports instead. 183 00:08:45.100 --> 00:08:47.850 Your life will be much easier, and really, 184 00:08:47.850 --> 00:08:50.030 you're not gonna encounter any problems with that. 185 00:08:50.030 --> 00:08:52.930 So thanks for joining me and I'll see you in the next one.