1 00:00:04,430 --> 00:00:06,500 Alright, so let's talk now about 2 00:00:06,500 --> 00:00:09,410 Any and All. So the names of these 3 00:00:09,410 --> 00:00:12,260 two functions pretty much describe what they 4 00:00:12,260 --> 00:00:15,289 do. All, that checks to see if the items 5 00:00:15,289 --> 00:00:18,320 in an iterable are true and Any, by 6 00:00:18,320 --> 00:00:20,630 contrast, checks to see if any of them 7 00:00:20,630 --> 00:00:23,570 are. Both functions take an iterable 8 00:00:23,570 --> 00:00:26,779 and return either true or false, depending on 9 00:00:26,779 --> 00:00:29,599 the values in the iterable. So let's have 10 00:00:29,599 --> 00:00:31,730 a look at some examples, to clarify their 11 00:00:31,730 --> 00:00:34,100 behavior and also see a couple of things 12 00:00:34,100 --> 00:00:36,260 to be wary of when you're using them. 13 00:00:36,260 --> 00:00:37,610 Now we're going to start by using a 14 00:00:37,610 --> 00:00:39,680 simple list for our iterable and I'm going to 15 00:00:39,680 --> 00:00:41,480 create a new Python file to do that, 16 00:00:41,480 --> 00:00:42,980 so let's do that. I'm going to create the 17 00:00:42,980 --> 00:00:50,210 file and call it anyall. Alright, so 18 00:00:50,210 --> 00:00:52,340 let's start typing now, so on line 1, 19 00:00:52,340 --> 00:00:55,370 entries equals left and right square 20 00:00:55,370 --> 00:00:58,280 braces. It's going to be 1, 2, 3, 21 00:00:58,280 --> 00:01:01,790 4, 5 separated by commas. On the 22 00:01:01,790 --> 00:01:03,729 first, on line three, we're going to print 23 00:01:03,729 --> 00:01:07,460 parentheses all colon left and right 24 00:01:07,460 --> 00:01:10,540 curly braces ending double quote comma 25 00:01:10,540 --> 00:01:15,470 format and in parentheses, all parenthesis 26 00:01:15,470 --> 00:01:18,500 entries, and the closing parenthesis. On 27 00:01:18,500 --> 00:01:20,420 the next line, we're going to do the same 28 00:01:20,420 --> 00:01:22,760 but for Any, so in double quotes after 29 00:01:22,760 --> 00:01:26,090 the print, any colon then our left and 30 00:01:26,090 --> 00:01:28,400 right curly braces closing double quote 31 00:01:28,400 --> 00:01:31,730 dot format and left parenthesis, 32 00:01:31,730 --> 00:01:34,430 any, left parenthesis entries and the closing 33 00:01:34,430 --> 00:01:37,580 right parenthesis. And I'm going 34 00:01:37,580 --> 00:01:39,740 to actually change this. What 35 00:01:39,740 --> 00:01:45,340 I'm going to do is, I'm gonna run it first, so let's do that. 36 00:01:45,340 --> 00:01:48,620 So you can see any and all have both 37 00:01:48,620 --> 00:01:50,900 returned true here, so basically, both 38 00:01:50,900 --> 00:01:52,760 functions are taking an iterable 39 00:01:52,760 --> 00:01:55,370 and returning either true or false, depending 40 00:01:55,370 --> 00:01:58,820 on the values in the iterable. And again 41 00:01:58,820 --> 00:02:01,010 in this case, both functions, as you can 42 00:02:01,010 --> 00:02:03,020 see in the run pane, are returning true. 43 00:02:03,020 --> 00:02:04,850 Now the reason that all is returning 44 00:02:04,850 --> 00:02:07,430 true is because all the items in the 45 00:02:07,430 --> 00:02:09,949 list of true values, and any value 46 00:02:09,949 --> 00:02:12,230 returns true because at least one of 47 00:02:12,230 --> 00:02:14,749 them is. Now I'm going to review what we 48 00:02:14,749 --> 00:02:17,389 mean by a true value in a moment, but firstly 49 00:02:17,389 --> 00:02:18,170 though, let's just 50 00:02:18,170 --> 00:02:21,140 see another example. On line 6 51 00:02:21,140 --> 00:02:22,480 I'm going to start by typing print 52 00:02:22,480 --> 00:02:25,670 parenthesis, in double quotes Iterable, 53 00:02:25,670 --> 00:02:30,110 with a single quote False closing single 54 00:02:30,110 --> 00:02:32,060 quote value, so that's our heading on 55 00:02:32,060 --> 00:02:33,500 that line. Then we're going to do, on 56 00:02:33,500 --> 00:02:36,500 line 7, entries with, underscore with 57 00:02:36,500 --> 00:02:40,700 that is, underscore zero is equal to, then 58 00:02:40,700 --> 00:02:43,580 in left and right square braces 1, 2 59 00:02:43,580 --> 00:02:49,640 0, 4, 5 and let's just take a 60 00:02:49,640 --> 00:02:53,450 copy of any, all and any. Paste it in 61 00:02:53,450 --> 00:02:55,370 and then we'll just change, so it's 62 00:02:55,370 --> 00:02:57,140 actually printing out the values 63 00:02:57,140 --> 00:03:00,220 from our second entry there. Entries with zero, 64 00:03:00,220 --> 00:03:05,600 entries with zero. What I might do 65 00:03:05,600 --> 00:03:08,959 is, just take the opportunity here to move 66 00:03:08,959 --> 00:03:10,610 the run window to the right hand side, so 67 00:03:10,610 --> 00:03:11,600 we can see the output a little bit 68 00:03:11,600 --> 00:03:14,900 better and now you've seen that code, 69 00:03:14,900 --> 00:03:16,220 or typed that code in, rather, let's actually 70 00:03:16,220 --> 00:03:19,580 run it. And you can see there, Iterable 71 00:03:19,580 --> 00:03:22,760 with a False value, all is returning 72 00:03:22,760 --> 00:03:25,180 False there but any is returning True. 73 00:03:25,180 --> 00:03:27,470 So contrasting that to the previous 74 00:03:27,470 --> 00:03:30,680 example, where all returned True. So any 75 00:03:30,680 --> 00:03:32,540 still returning True here in this second 76 00:03:32,540 --> 00:03:35,239 example, and it's basically asking, does 77 00:03:35,239 --> 00:03:38,239 the list contain any true items? 78 00:03:38,239 --> 00:03:39,709 Alright, so now that we've seen that, 79 00:03:39,709 --> 00:03:41,780 so what do we mean when we say true items 80 00:03:41,780 --> 00:03:43,480 or true values? What do we mean by that? 81 00:03:43,480 --> 00:03:46,280 Well if you can recall, way back early on 82 00:03:46,280 --> 00:03:47,840 in the course, I showed you how Python 83 00:03:47,840 --> 00:03:50,780 interprets some values as false 84 00:03:50,780 --> 00:03:53,090 and everything else as true. So what I'm 85 00:03:53,090 --> 00:03:54,650 going to do is paste that code back in, 86 00:03:54,650 --> 00:03:56,870 and we'll run it again just to refresh 87 00:03:56,870 --> 00:04:00,380 your memory there. I'm going to do that 88 00:04:00,380 --> 00:04:02,650 on line 12, 89 00:04:02,650 --> 00:04:04,820 and I'll just close the run window for 90 00:04:04,820 --> 00:04:09,620 now, and there's the example. You can see 91 00:04:09,620 --> 00:04:11,510 the code that I've pasted in there. 92 00:04:11,510 --> 00:04:13,820 Now I've used the bool function to convert 93 00:04:13,820 --> 00:04:16,040 the value to true or false, as Python 94 00:04:16,040 --> 00:04:17,959 sees it. By printing the result of 95 00:04:17,959 --> 00:04:20,180 calling bool for each of the items, we 96 00:04:20,180 --> 00:04:22,460 can confirm that Python hopefully does 97 00:04:22,460 --> 00:04:24,530 see them as false. Everything else though, 98 00:04:24,530 --> 00:04:26,900 will be evaluated as true if we use 99 00:04:26,900 --> 00:04:28,460 it as a condition but let's just tell run 100 00:04:28,460 --> 00:04:31,240 this example first. 101 00:04:31,240 --> 00:04:33,260 You can see down here, we're getting the 102 00:04:33,260 --> 00:04:34,940 examples here, values interpreted as 103 00:04:34,940 --> 00:04:37,820 False in Python. False is false, None 104 00:04:37,820 --> 00:04:40,880 is false, 0 is false, 0.0 is false, an empty 105 00:04:40,880 --> 00:04:41,660 list is false, 106 00:04:41,660 --> 00:04:43,640 empty tuple false, empty string false, 107 00:04:43,640 --> 00:04:45,350 an empty string with double quotes is 108 00:04:45,350 --> 00:04:47,300 termed false and entry mapping 109 00:04:47,300 --> 00:04:50,210 also false. Now that's pretty clear now, but cos 110 00:04:50,210 --> 00:04:52,130 we've used the bool function, and by 111 00:04:52,130 --> 00:04:53,660 printing the result of calling bool for 112 00:04:53,660 --> 00:04:55,310 each of these items, as I mentioned, we're 113 00:04:55,310 --> 00:04:56,870 confirming that Python does in fact see 114 00:04:56,870 --> 00:04:58,760 them as false. Everything else however, 115 00:04:58,760 --> 00:05:01,760 will be evaluated as true if we use it 116 00:05:01,760 --> 00:05:04,160 as a condition. A quick example should 117 00:05:04,160 --> 00:05:06,080 help with that, so let's just type that 118 00:05:06,080 --> 00:05:15,440 in. Okay, okay so we're going to start on 119 00:05:15,440 --> 00:05:18,020 line 25, print 2 parentheses double 120 00:05:18,020 --> 00:05:21,830 quotes, an equal in it, times 80, so we 121 00:05:21,830 --> 00:05:23,840 get a nice little heading there and then 122 00:05:23,840 --> 00:05:28,850 we're going to do name equals double 123 00:05:28,850 --> 00:05:30,440 quotes, two double quotes, so we're going to 124 00:05:30,440 --> 00:05:33,080 start with an empty string, if name colon. 125 00:05:33,080 --> 00:05:35,680 On the next line, then print Hello 126 00:05:35,680 --> 00:05:38,930 left and right curly braces closing double 127 00:05:38,930 --> 00:05:43,460 quote dot format name. Then we're gonna have an 128 00:05:43,460 --> 00:05:45,470 else on the next line, else colon then 129 00:05:45,470 --> 00:05:51,380 print Welcome, person with no name, double 130 00:05:51,380 --> 00:05:56,270 quotes closing parenthesis. So when we're 131 00:05:56,270 --> 00:05:59,420 testing name on line 27, it evaluates to 132 00:05:59,420 --> 00:06:00,770 false and we should get the welcome 133 00:06:00,770 --> 00:06:02,720 message printed out. So let's actually run 134 00:06:02,720 --> 00:06:04,910 that and confirm that is the case. 135 00:06:04,910 --> 00:06:06,470 You can see down here in the output, or 136 00:06:06,470 --> 00:06:07,610 at the right hand side of the screen, 137 00:06:07,610 --> 00:06:09,680 Welcome, person with no name, and that's 138 00:06:09,680 --> 00:06:11,030 consistent with the fact that an empty 139 00:06:11,030 --> 00:06:12,590 string higher up on the run 140 00:06:12,590 --> 00:06:15,260 window output there, is also returning false, 141 00:06:15,260 --> 00:06:17,270 and if we change that to actually put a name 142 00:06:17,270 --> 00:06:19,280 on line 26 instead of the empty string 143 00:06:19,280 --> 00:06:23,060 and run it again, this time we're getting 144 00:06:23,060 --> 00:06:24,710 Hello Tim because it's no longer being 145 00:06:24,710 --> 00:06:27,350 evaluated as false. In fact name is now 146 00:06:27,350 --> 00:06:29,450 true because it has got some content. 147 00:06:29,450 --> 00:06:31,940 It's not empty, in other words. So 148 00:06:31,940 --> 00:06:35,450 closing now the run pane again, 149 00:06:35,450 --> 00:06:37,160 and going back to our code at the top there, 150 00:06:37,160 --> 00:06:39,410 our entries with zero list, it 151 00:06:39,410 --> 00:06:41,690 should now be obvious as to why all return 152 00:06:41,690 --> 00:06:44,120 false. Zero was interpreted as 153 00:06:44,120 --> 00:06:46,310 false, so all the items in the 154 00:06:46,310 --> 00:06:48,979 list aren't true. Alright, so that's all and any. 155 00:06:48,979 --> 00:06:51,800 They both take an Iterable and can be 156 00:06:51,800 --> 00:06:54,590 very useful to check, or for checking the 157 00:06:54,590 --> 00:06:57,050 items in the iterable for consistency. 158 00:06:57,050 --> 00:06:59,210 This becomes even more useful when we 159 00:06:59,210 --> 00:07:00,919 combine them with a comprehension 160 00:07:00,919 --> 00:07:03,680 or generate our expression, which is why 161 00:07:03,680 --> 00:07:05,240 we've included them in this section on 162 00:07:05,240 --> 00:07:07,160 comprehensions. If you recall, 163 00:07:07,160 --> 00:07:08,630 I did mention 164 00:07:08,630 --> 00:07:10,010 that there's a couple of things to be wary of. 165 00:07:10,010 --> 00:07:13,580 The main one is how all behaves with an 166 00:07:13,580 --> 00:07:16,040 empty iterable. So I'm going to create a 167 00:07:16,040 --> 00:07:17,870 new file for this just to help clarify. 168 00:07:17,870 --> 00:07:21,199 So New, Python file, and we'll call 169 00:07:21,199 --> 00:07:26,539 this one allgotcha, and I'm gonna paste 170 00:07:26,539 --> 00:07:30,440 in these three lines from the previous 171 00:07:30,440 --> 00:07:31,550 example we we're working on, 172 00:07:31,550 --> 00:07:33,410 previous file. Alright, so let's run 173 00:07:33,410 --> 00:07:38,449 that, and again we can see there, on the 174 00:07:38,449 --> 00:07:40,400 right-hand side, both the functions are 175 00:07:40,400 --> 00:07:41,930 returning true as we saw earlier in the 176 00:07:41,930 --> 00:07:45,139 video, but what happens if the iterable 177 00:07:45,139 --> 00:07:48,139 is empty? Let's change that to making an 178 00:07:48,139 --> 00:07:51,770 empty list on line 1. Before I run the 179 00:07:51,770 --> 00:07:53,120 program though, have a think about what 180 00:07:53,120 --> 00:07:54,740 you'd expect to happen. What would you 181 00:07:54,740 --> 00:07:57,080 expect to happen, given that now the list 182 00:07:57,080 --> 00:08:01,340 is empty. So let's now run this and 183 00:08:01,340 --> 00:08:04,130 you can see that any behaves as expected 184 00:08:04,130 --> 00:08:06,320 and returns false, and that makes sense 185 00:08:06,320 --> 00:08:07,910 because the list doesn't contain any 186 00:08:07,910 --> 00:08:09,979 items that could be true. Now where you 187 00:08:09,979 --> 00:08:11,539 may have expected a different 188 00:08:11,539 --> 00:08:14,180 result though, is all. As you can see there 189 00:08:14,180 --> 00:08:16,910 in the output, all is returning true. Now 190 00:08:16,910 --> 00:08:18,740 that's the documented behavior so it's 191 00:08:18,740 --> 00:08:20,690 not a bug, but I wouldn't have expected 192 00:08:20,690 --> 00:08:22,760 that result, and that's why I've included 193 00:08:22,760 --> 00:08:24,289 this because it's something that can 194 00:08:24,289 --> 00:08:26,660 catch you out. If there's a possibility 195 00:08:26,660 --> 00:08:28,970 that your list, or whatever iterable 196 00:08:28,970 --> 00:08:31,099 you're checking can be empty, then you 197 00:08:31,099 --> 00:08:33,169 need to test for that as well. Now we've 198 00:08:33,169 --> 00:08:35,150 just seen that an empty list evaluates 199 00:08:35,150 --> 00:08:37,610 as false in a boolean expression, so you 200 00:08:37,610 --> 00:08:39,440 can generally, write something 201 00:08:39,440 --> 00:08:42,289 like this; so I'm going to just 202 00:08:42,289 --> 00:08:43,549 close down this run window so we get more 203 00:08:43,549 --> 00:08:46,220 output, but you can do something like, on 204 00:08:46,220 --> 00:08:51,410 line 3, if entries then we go print 205 00:08:51,410 --> 00:08:55,240 all, else 206 00:08:55,240 --> 00:09:00,080 print false in double quotes. Then on the 207 00:09:00,080 --> 00:09:01,010 next line, we're going to print 208 00:09:01,010 --> 00:09:04,160 the result of calling any. If you run that 209 00:09:04,160 --> 00:09:08,180 now, we're getting false returned in both 210 00:09:08,180 --> 00:09:11,420 scenarios, which is now more correct. So 211 00:09:11,420 --> 00:09:13,310 this would be a better way of actually 212 00:09:13,310 --> 00:09:14,930 writing a code there, because we're now 213 00:09:14,930 --> 00:09:17,600 using the fact that conditional if 214 00:09:17,600 --> 00:09:19,670 is evaluating the empty list as false in a 215 00:09:19,670 --> 00:09:22,220 boolean expression. Another thing to be aware 216 00:09:22,220 --> 00:09:24,380 of is combining the check for an empty 217 00:09:24,380 --> 00:09:27,020 list in a single boolean expression. 218 00:09:27,020 --> 00:09:27,980 So you might be tempted to do 219 00:09:27,980 --> 00:09:30,250 something along these lines; 220 00:09:30,250 --> 00:09:34,839 result equals entries and all 221 00:09:34,839 --> 00:09:41,600 parentheses entries print result. So if 222 00:09:41,600 --> 00:09:45,020 we run that, so as you can see, we get 223 00:09:45,020 --> 00:09:47,570 the result printing as an empty list, not 224 00:09:47,570 --> 00:09:50,660 false as we wanted. So in this case, we 225 00:09:50,660 --> 00:09:53,060 have to be explicit. So we would change 226 00:09:53,060 --> 00:09:55,760 that to result equals bool, call to bool, 227 00:09:55,760 --> 00:10:01,399 entries and all entries, like so. If we 228 00:10:01,399 --> 00:10:04,820 run that, we're now correctly getting 229 00:10:04,820 --> 00:10:07,430 false showing. Basically, now behaves as 230 00:10:07,430 --> 00:10:10,040 we want. So there you go, two gotchas for 231 00:10:10,040 --> 00:10:12,470 the price of one. I'll go over some more 232 00:10:12,470 --> 00:10:14,660 examples of any and all in a later video. 233 00:10:14,660 --> 00:10:17,120 We're going to need some data for the 234 00:10:17,120 --> 00:10:18,470 examples, and we really don't want to 235 00:10:18,470 --> 00:10:20,630 spend a lot of time typing it all in, so in 236 00:10:20,630 --> 00:10:22,339 the resources section for this video, 237 00:10:22,339 --> 00:10:25,490 you'll find the file data.py. Download 238 00:10:25,490 --> 00:10:27,290 that file and place it in your project 239 00:10:27,290 --> 00:10:29,180 directory, and we'll make use of that in 240 00:10:29,180 --> 00:10:30,950 the next video. I won't be 241 00:10:30,950 --> 00:10:32,930 using comprehensions in the next video. 242 00:10:32,930 --> 00:10:34,700 Those examples for comprehensions 243 00:10:34,700 --> 00:10:36,589 will be in the video after that. The next 244 00:10:36,589 --> 00:10:38,240 one, though, is a short one to introduce 245 00:10:38,240 --> 00:10:41,060 named tuples. So I'll see you in the 246 00:10:41,060 --> 00:10:43,480 next video.