1 1 00:00:00,630 --> 00:00:02,750 Hi guys and welcome back. In this video, 2 2 00:00:02,750 --> 00:00:05,663 we're going to talk about relative imports in Python. 3 3 00:00:05,663 --> 00:00:07,600 This is something that's really confusing 4 4 00:00:07,600 --> 00:00:10,200 for new Python beginners, and to be honest, 5 5 00:00:10,200 --> 00:00:11,880 it's a bit weird. 6 6 00:00:11,880 --> 00:00:14,260 And you're not going to be using them very much at all 7 7 00:00:14,260 --> 00:00:15,580 but I just wanted to talk about them 8 8 00:00:15,580 --> 00:00:17,680 so that you all use them precisely 9 9 00:00:17,680 --> 00:00:19,330 because they work very differently 10 10 00:00:19,330 --> 00:00:21,540 than what you might expect. 11 11 00:00:21,540 --> 00:00:24,750 What I've got here is four files now. 12 12 00:00:24,750 --> 00:00:29,140 I've got code, and mymodule in the same folder. 13 13 00:00:29,140 --> 00:00:34,140 Then we've got our libs folder that contains mylib. 14 14 00:00:34,790 --> 00:00:37,150 And then we've got our operations folder 15 15 00:00:37,150 --> 00:00:39,540 that contains operator. 16 16 00:00:39,540 --> 00:00:44,493 So code imports mymodule, mymodule imports libs.mylib, 17 17 00:00:45,470 --> 00:00:49,950 and mylib imports libs.operations.operator. 18 18 00:00:49,950 --> 00:00:52,290 And each one prints out their name. 19 19 00:00:52,290 --> 00:00:57,290 So if we press play right now, what you get back is-- 20 20 00:00:57,680 --> 00:00:59,950 Well first of all, something important to note is that-- 21 21 00:00:59,950 --> 00:01:01,170 I may not have mentioned it in the last video, 22 22 00:01:01,170 --> 00:01:04,010 is that when you run the import, 23 23 00:01:04,010 --> 00:01:06,130 that immediately jumps into the next file 24 24 00:01:06,130 --> 00:01:07,180 and starts running it. 25 25 00:01:07,180 --> 00:01:10,980 So of course, code.py imports mymodule 26 26 00:01:10,980 --> 00:01:12,820 so that stops code.py from running 27 27 00:01:12,820 --> 00:01:16,470 and Python jumps to mymodule. This imports mylib. 28 28 00:01:16,470 --> 00:01:18,440 So this stops running and jumps to mylib. 29 29 00:01:18,440 --> 00:01:20,250 This imports operator so that stops running 30 30 00:01:20,250 --> 00:01:23,420 and jumps to operator, and that prints. 31 31 00:01:23,420 --> 00:01:27,100 Then we go back to mylib and then we print, 32 32 00:01:27,100 --> 00:01:29,820 then we go back to mymodule, then we print, 33 33 00:01:29,820 --> 00:01:31,600 then we go back to code and then we print. 34 34 00:01:31,600 --> 00:01:33,530 So that's why the order here is reversed 35 35 00:01:33,530 --> 00:01:35,730 from the order in which the files are running. 36 36 00:01:35,730 --> 00:01:38,250 Code is running first but that prints out last 37 37 00:01:38,250 --> 00:01:42,200 because of that tree of imports that's going on. 38 38 00:01:42,200 --> 00:01:44,530 So this is not relative imports. 39 39 00:01:44,530 --> 00:01:48,600 These are just absolute imports where you have to define 40 40 00:01:48,600 --> 00:01:50,350 the path that you're importing from. 41 41 00:01:50,350 --> 00:01:55,180 So here and the path is libs.operations.operator 42 42 00:01:55,180 --> 00:01:58,640 and we're doing from libs.operations import operator, 43 43 00:01:58,640 --> 00:02:02,980 or you could do import libs.opererations.operator 44 44 00:02:02,980 --> 00:02:04,290 if you preferred, although then 45 45 00:02:04,290 --> 00:02:06,020 you would have to access things like 46 46 00:02:06,020 --> 00:02:08,980 libs.operations.operator.divide. 47 47 00:02:08,980 --> 00:02:13,270 If a divide function was defined inside that file, 48 48 00:02:13,270 --> 00:02:14,103 which it's not. 49 49 00:02:14,103 --> 00:02:15,910 At the moment, nothing's defined inside these files. 50 50 00:02:15,910 --> 00:02:17,990 They're just printing out their names. 51 51 00:02:17,990 --> 00:02:20,870 So that is absolute imports. 52 52 00:02:20,870 --> 00:02:23,250 Let's talk about relative imports. 53 53 00:02:23,250 --> 00:02:27,330 A relative import is one that can import 54 54 00:02:27,330 --> 00:02:31,900 from the current folder that the file is in. 55 55 00:02:31,900 --> 00:02:36,730 But it cannot import unless there is a folder name 56 56 00:02:36,730 --> 00:02:39,950 in the import path, in the module path. 57 57 00:02:39,950 --> 00:02:42,784 So, here's what that means. 58 58 00:02:42,784 --> 00:02:46,160 Libs.mylib when it prints out the name 59 59 00:02:46,160 --> 00:02:49,190 you can see that there is a folder inside the import path 60 60 00:02:49,190 --> 00:02:51,530 that is separated from other things in the path 61 61 00:02:51,530 --> 00:02:53,390 by a full stop, a period. 62 62 00:02:53,390 --> 00:02:55,250 So here you've got the libs folder 63 63 00:02:55,250 --> 00:02:57,370 and inside it you've got the mylib file. 64 64 00:02:57,370 --> 00:02:58,550 You can tell this is the file 65 65 00:02:58,550 --> 00:03:02,620 because it's the last thing in the import. 66 66 00:03:02,620 --> 00:03:05,890 Similarly, the operator.py has the file operator, 67 67 00:03:05,890 --> 00:03:07,180 that's where we're importing from 68 68 00:03:07,180 --> 00:03:10,360 and two folders, operations and libs. 69 69 00:03:10,360 --> 00:03:13,610 So, from these two you can do relative imports 70 70 00:03:13,610 --> 00:03:15,200 because there is a folder. 71 71 00:03:15,200 --> 00:03:17,270 From these two you cannot do relative imports 72 72 00:03:17,270 --> 00:03:19,080 because there's no folder. 73 73 00:03:19,080 --> 00:03:20,590 So let me show you what happens 74 74 00:03:20,590 --> 00:03:22,490 if you try to do a relative import 75 75 00:03:22,490 --> 00:03:24,640 and you don't have a folder. 76 76 00:03:24,640 --> 00:03:26,470 In order to do a relative import 77 77 00:03:26,470 --> 00:03:28,680 you need to use the from syntax. 78 78 00:03:28,680 --> 00:03:33,420 So you can do from .mymodule import divide let's say 79 79 00:03:33,420 --> 00:03:36,173 and I'm going to just add a divide function here. 80 80 00:03:38,780 --> 00:03:40,660 So (mumbles) divide function there it doesn't do anything 81 81 00:03:40,660 --> 00:03:44,220 and we're gonna try to import it from .mymodule. 82 82 00:03:44,220 --> 00:03:47,080 So what that means is from the current folder 83 83 00:03:47,080 --> 00:03:51,090 look at the mymodule file and import the divide function. 84 84 00:03:51,090 --> 00:03:56,090 So that makes sense because mymodule is in the same folder 85 85 00:03:56,720 --> 00:04:00,200 as code.py. You can see down here they're in the same folder 86 86 00:04:00,200 --> 00:04:02,160 so they should be fine. 87 87 00:04:02,160 --> 00:04:04,880 But when you try to do that, 88 88 00:04:04,880 --> 00:04:09,880 what it does is it tries to import from __main.mymodule. 89 89 00:04:12,230 --> 00:04:16,270 So as you can see because the name of this file was __main 90 90 00:04:16,270 --> 00:04:18,270 and it doesn't have a folder, 91 91 00:04:18,270 --> 00:04:21,890 it tries to import from the current place it's in 92 92 00:04:21,890 --> 00:04:24,460 and Python won't let you do that. 93 93 00:04:24,460 --> 00:04:28,120 If you are importing from the file you run, 94 94 00:04:28,120 --> 00:04:31,300 you can't use relative imports. 95 95 00:04:31,300 --> 00:04:36,300 Going into mymodule.py you could do from .libs import mylib 96 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 97 00:04:39,710 --> 00:04:43,010 the libs folder inside the current folder, 98 98 00:04:43,010 --> 00:04:44,980 that's what the dot means. 99 99 00:04:44,980 --> 00:04:47,523 But again, if you try to run this code, 100 100 00:04:48,570 --> 00:04:51,370 you're going to get that you attempted a relative import 101 101 00:04:51,370 --> 00:04:54,830 with no known parent package. 102 102 00:04:54,830 --> 00:04:58,770 Again, mymodule has no information about the folder it's in 103 103 00:04:58,770 --> 00:05:01,713 so Python can't do a relative import from it. 104 104 00:05:02,890 --> 00:05:05,760 I'll show you again these paths here, 105 105 00:05:05,760 --> 00:05:07,270 because what you've got-- 106 106 00:05:07,270 --> 00:05:10,093 Oh, sorry I'll run code.py so it's the same as before. 107 107 00:05:11,040 --> 00:05:15,510 What you've got is that mymodule and main 108 108 00:05:15,510 --> 00:05:17,750 are at the top level. 109 109 00:05:17,750 --> 00:05:19,580 When you're trying to do a relative import, 110 110 00:05:19,580 --> 00:05:22,320 what Python's going to do is it's going to remove the file 111 111 00:05:22,320 --> 00:05:23,870 and it's just going to try to append 112 112 00:05:23,870 --> 00:05:27,670 whatever you import from into the rest of the import path. 113 113 00:05:27,670 --> 00:05:31,900 So if we go to mylib and then we do from .operations 114 114 00:05:31,900 --> 00:05:35,387 import operator, what that's gonna do is it's gonna say, 115 115 00:05:35,387 --> 00:05:40,120 "Okay, mylib, you are inside libs.mylib." 116 116 00:05:40,120 --> 00:05:43,140 So, because you're trying to do a relative import, 117 117 00:05:43,140 --> 00:05:45,140 we're going to remove the file 118 118 00:05:45,140 --> 00:05:48,090 and we're gonna try to put operations at the end 119 119 00:05:48,090 --> 00:05:49,070 and import from there. 120 120 00:05:49,070 --> 00:05:52,180 So here it'll work because it'll do libs.operations 121 121 00:05:52,180 --> 00:05:54,500 and then it'll import operator from that. 122 122 00:05:54,500 --> 00:05:57,130 So if I run code.py again, 123 123 00:05:57,130 --> 00:05:59,030 you can see that it all works fine. 124 124 00:05:59,030 --> 00:06:01,050 There's no errors whatsoever. 125 125 00:06:01,050 --> 00:06:05,880 However, if by any reason you want to run your mylib file, 126 126 00:06:05,880 --> 00:06:08,950 for example to debug it or run some code inside it, 127 127 00:06:08,950 --> 00:06:11,010 make sure it works or something like that, 128 128 00:06:11,010 --> 00:06:13,730 you won't be able to because, of course, 129 129 00:06:13,730 --> 00:06:16,540 this now becomes main, if you run it, 130 130 00:06:16,540 --> 00:06:19,440 and then you can't use relative imports from inside it. 131 131 00:06:19,440 --> 00:06:22,180 So, if you are going to use relative imports, 132 132 00:06:22,180 --> 00:06:25,700 you always have to run the same file at the top level, 133 133 00:06:25,700 --> 00:06:28,093 otherwise you may encounter some issues. 134 134 00:06:28,950 --> 00:06:30,203 Going into operator.py, 135 135 00:06:31,110 --> 00:06:35,660 you can actually do from ..mylib import star, let's say, 136 136 00:06:35,660 --> 00:06:36,900 and what this does in Python 137 137 00:06:36,900 --> 00:06:39,640 is it accesses the parent folder. 138 138 00:06:39,640 --> 00:06:43,800 So again if operator is inside libs.operations, 139 139 00:06:43,800 --> 00:06:47,120 dot dot is going to try to remove the operation 140 140 00:06:48,111 --> 00:06:50,120 and go direct to the previous one. 141 141 00:06:50,120 --> 00:06:54,130 So it'll try to do libs.mylib. That's what the dot dot means 142 142 00:06:54,130 --> 00:06:57,240 it just skips the parent folder and goes up to the next one. 143 143 00:06:57,240 --> 00:06:59,810 So, of course in order to do that, 144 144 00:06:59,810 --> 00:07:02,010 you need to be at least two levels deep. 145 145 00:07:02,010 --> 00:07:04,950 Otherwise if you try to do that for example from libs.mylib, 146 146 00:07:04,950 --> 00:07:07,760 you're going to try to skip libs and go to the previous one, 147 147 00:07:07,760 --> 00:07:10,700 but there is no previous one, so you'll find that error. 148 148 00:07:10,700 --> 00:07:12,180 So, again in order to do this, 149 149 00:07:12,180 --> 00:07:14,990 you need to do something like that, 150 150 00:07:14,990 --> 00:07:17,493 and that you can see works totally fine. 151 151 00:07:19,040 --> 00:07:22,920 Let's go back to why we didn't print anything else out 152 152 00:07:22,920 --> 00:07:25,010 when we ran this code because as you can see 153 153 00:07:25,010 --> 00:07:27,650 this output is exactly identical to the one we had before, 154 154 00:07:27,650 --> 00:07:30,000 so it seems that this did nothing. 155 155 00:07:30,000 --> 00:07:32,400 But really what's happened is Python has realised 156 156 00:07:32,400 --> 00:07:37,010 that libs.mylib had already been imported by mymodule 157 157 00:07:37,010 --> 00:07:39,520 before we imported operator. 158 158 00:07:39,520 --> 00:07:41,560 So, it didn't try to import it again. 159 159 00:07:41,560 --> 00:07:45,490 This just reuses the import that's already on six modules. 160 160 00:07:45,490 --> 00:07:47,360 So that's why we didn't see any more output. 161 161 00:07:47,360 --> 00:07:50,480 mylib.py didn't run again when we tried to import this. 162 162 00:07:50,480 --> 00:07:53,020 It was already in dot modules. 163 163 00:07:53,020 --> 00:07:55,190 I also wanted to say that at any point in time 164 164 00:07:55,190 --> 00:07:58,820 if you wanted to import say operator.py from mymodule, 165 165 00:07:58,820 --> 00:08:01,123 you can do import libs.operations.operator, 166 166 00:08:02,160 --> 00:08:06,450 or of course, from libs.operations import operator. 167 167 00:08:06,450 --> 00:08:08,400 You can do that as well. 168 168 00:08:08,400 --> 00:08:10,620 By the way, this just means import everything 169 169 00:08:10,620 --> 00:08:13,270 that is inside this path here. 170 170 00:08:13,270 --> 00:08:15,300 So if there were multiple functions, 171 171 00:08:15,300 --> 00:08:16,470 you would import them all. 172 172 00:08:16,470 --> 00:08:18,720 If there's multiple variables defined in there, 173 173 00:08:18,720 --> 00:08:21,320 you would also import them, and so on. 174 174 00:08:21,320 --> 00:08:22,860 All right that's everything for this video. 175 175 00:08:22,860 --> 00:08:25,470 Thank you for joining me. I know this stuff is confusing, 176 176 00:08:25,470 --> 00:08:29,410 but my advice is to not use relative imports in Python. 177 177 00:08:29,410 --> 00:08:32,260 They are difficult to understand, they're confusing, 178 178 00:08:32,260 --> 00:08:35,220 they only work if you always run the same files, 179 179 00:08:35,220 --> 00:08:37,950 and they won't work if you try to run other files 180 180 00:08:37,950 --> 00:08:39,830 such as the ones that use relative imports 181 181 00:08:39,830 --> 00:08:42,290 for debugging or to try things out. 182 182 00:08:42,290 --> 00:08:45,100 So, don't use them. Use absolute imports instead. 183 183 00:08:45,100 --> 00:08:47,850 Your life will be much easier, and really, 184 184 00:08:47,850 --> 00:08:50,030 you're not gonna encounter any problems with that. 185 185 00:08:50,030 --> 00:08:52,930 So thanks for joining me and I'll see you in the next one.