WEBVTT 1 00:00:00.560 --> 00:00:02.630 Now finally there's quite a lot of changes 2 00:00:02.630 --> 00:00:05.910 to app.py as a result of this. 3 00:00:05.910 --> 00:00:08.600 But most changes that we're gonna make are simplifications 4 00:00:08.600 --> 00:00:12.240 to allow to reason about the code more easily. 5 00:00:12.240 --> 00:00:13.490 From now on we're gonna be dealing 6 00:00:13.490 --> 00:00:16.090 with objects and their actions or methods 7 00:00:16.090 --> 00:00:18.883 rather than database operations directly. 8 00:00:20.170 --> 00:00:24.293 So lets go over to app.py and start making our changes. 9 00:00:25.650 --> 00:00:28.700 The first thing is that down here at the very bottom 10 00:00:28.700 --> 00:00:32.390 we've got this way of passing connections about. 11 00:00:32.390 --> 00:00:34.380 Passing a connection that we create up here 12 00:00:34.380 --> 00:00:37.470 to every function but we no longer need that because 13 00:00:37.470 --> 00:00:40.320 our models are in charge of creating the connection. 14 00:00:40.320 --> 00:00:42.143 So we're gonna get rid of that. 15 00:00:43.620 --> 00:00:45.170 Now over here in connections.py 16 00:00:46.120 --> 00:00:48.900 we are loading the connection, creating one, 17 00:00:48.900 --> 00:00:52.010 so what we're gonna do is go back to app.py 18 00:00:52.010 --> 00:00:54.640 and instead of using this line we're 19 00:00:54.640 --> 00:00:58.410 gonna use create-connection, we do have to import that 20 00:00:58.410 --> 00:01:00.860 so I'm going to do that. 21 00:01:00.860 --> 00:01:04.960 Now note that we're no longer calling load_dotenv here, 22 00:01:04.960 --> 00:01:05.910 so what I'm gonna do is I'm gonna 23 00:01:05.910 --> 00:01:08.110 move this over to connections.py 24 00:01:08.110 --> 00:01:12.080 and we're no longer going to need all of this. 25 00:01:12.080 --> 00:01:13.880 For now I'm gonna get rid of this input 26 00:01:13.880 --> 00:01:15.190 but we're gonna bring it back later on 27 00:01:15.190 --> 00:01:17.620 so I'm just gonna copy load_dotenv 28 00:01:17.620 --> 00:01:20.110 and bring it over to connections.py 29 00:01:21.110 --> 00:01:23.170 and of course we do have to import it 30 00:01:23.170 --> 00:01:24.753 so we're gonna import that. 31 00:01:26.590 --> 00:01:28.430 That simplifies our menu quite a bit. 32 00:01:28.430 --> 00:01:30.550 Notice the PyCharm is complaining that 33 00:01:30.550 --> 00:01:32.440 we're not passing in the required arguments 34 00:01:32.440 --> 00:01:33.970 but that's 'cause we're gonna go through 35 00:01:33.970 --> 00:01:36.890 and get rid of all of these connections 36 00:01:36.890 --> 00:01:38.963 that we don't need anymore. 37 00:01:41.310 --> 00:01:44.880 Lets start with the top function prompt_create_poll. 38 00:01:44.880 --> 00:01:48.550 Notice that prompt_create_poll is directly calling 39 00:01:48.550 --> 00:01:51.920 the database.create_poll function passing in the poll_title, 40 00:01:51.920 --> 00:01:56.070 owner and the list of strings each representing an option. 41 00:01:56.070 --> 00:01:59.010 We now want to use our poll and option 42 00:01:59.010 --> 00:02:00.890 classes to do this instead. 43 00:02:00.890 --> 00:02:02.690 First things we're going to go ahead 44 00:02:02.690 --> 00:02:04.540 and fix our import slightly here 45 00:02:04.540 --> 00:02:07.350 and we're going to import our models. 46 00:02:07.350 --> 00:02:11.940 So we're gonna do from models.option import_Option 47 00:02:11.940 --> 00:02:16.570 and from models our poll import_Poll. 48 00:02:16.570 --> 00:02:19.670 Now we can come back down here and start making our changes. 49 00:02:19.670 --> 00:02:22.710 The first thing, when we have the title and the owner 50 00:02:22.710 --> 00:02:24.360 we can create a poll and we can say 51 00:02:24.360 --> 00:02:29.360 poll = Poll with title or rather poll_title and poll_owner. 52 00:02:30.230 --> 00:02:32.580 Then we can save this poll to the database. 53 00:02:32.580 --> 00:02:35.380 So we're gonna do poll.save. 54 00:02:35.380 --> 00:02:38.240 And now we no longer need this options list, 55 00:02:38.240 --> 00:02:40.870 because what we're gonna do is admittedly 56 00:02:40.870 --> 00:02:43.270 a bit less efficient but just down to 57 00:02:43.270 --> 00:02:45.370 how we've re-architectured our code. 58 00:02:45.370 --> 00:02:47.900 While we've got a new option valid 59 00:02:47.900 --> 00:02:52.900 then we're gonna do poll.add.option(new_option) 60 00:02:53.050 --> 00:02:55.700 and we no longer need this call down here. 61 00:02:55.700 --> 00:02:58.630 So now you can see we've simplified our code a fair bit 62 00:02:58.630 --> 00:03:01.680 in exchange for losing some efficiency 63 00:03:01.680 --> 00:03:03.670 when it comes to dealing with our database. 64 00:03:03.670 --> 00:03:05.700 This is a trade off that you're gonna make a lot 65 00:03:05.700 --> 00:03:08.690 when you're working with an ORM, for example. 66 00:03:08.690 --> 00:03:10.450 And if you don't know what an ORM is, 67 00:03:10.450 --> 00:03:12.440 we'll talk about that later on. 68 00:03:12.440 --> 00:03:14.767 Let's take a look at list_open_polls. 69 00:03:14.767 --> 00:03:16.550 At the moment it's accessing this 70 00:03:16.550 --> 00:03:19.130 because it wants the polls to be coming from the database. 71 00:03:19.130 --> 00:03:21.710 But now we're gonna use our model to do that 72 00:03:21.710 --> 00:03:24.723 so will do polls = Poll.all, 73 00:03:25.780 --> 00:03:27.380 and that is gonna go into the database 74 00:03:27.380 --> 00:03:29.063 and fetch all the polls. 75 00:03:30.080 --> 00:03:31.270 Note that you don't really need that 76 00:03:31.270 --> 00:03:33.520 you could just put that directly in here 77 00:03:33.520 --> 00:03:34.970 and that shortens you code a bit more 78 00:03:34.970 --> 00:03:37.410 and I think that's still pretty reasonable. 79 00:03:37.410 --> 00:03:40.410 But we can't use the destructuring here 80 00:03:40.410 --> 00:03:43.290 because a poll is not a destructurable thing 81 00:03:43.290 --> 00:03:45.160 so we do have to do poll, 82 00:03:45.160 --> 00:03:50.122 but then you can do (poll.id) like that, 83 00:03:50.122 --> 00:03:53.490 (poll.title) (poll.owner) instead. 84 00:03:53.490 --> 00:03:55.800 Alternatively you could put all of this 85 00:03:55.800 --> 00:03:58.830 inside the STR method of the poll object 86 00:03:58.830 --> 00:04:00.050 and then you can just print the poll, 87 00:04:00.050 --> 00:04:01.680 if that makes it simpler for you 88 00:04:01.680 --> 00:04:03.870 then by all means you can do that. 89 00:04:03.870 --> 00:04:06.360 Now let's move over to prompt_vote_poll. 90 00:04:06.360 --> 00:04:07.410 Note that the first thing we're 91 00:04:07.410 --> 00:04:10.180 doing here is grab a poll ID. 92 00:04:10.180 --> 00:04:11.430 That means that it's very likely 93 00:04:11.430 --> 00:04:12.590 the next thing we're gonna do 94 00:04:12.590 --> 00:04:15.160 is get the associated poll object 95 00:04:15.160 --> 00:04:18.290 so that we can interact with the database through that. 96 00:04:18.290 --> 00:04:22.357 So let's do that poll = Poll.get with the (poll.id). 97 00:04:23.760 --> 00:04:26.610 Now the poll options, we know that we no longer 98 00:04:26.610 --> 00:04:28.730 need to access the database here like that 99 00:04:28.730 --> 00:04:31.730 because we can just .options. 100 00:04:31.730 --> 00:04:34.660 So when it comes to printing the poll options 101 00:04:34.660 --> 00:04:37.630 we could just grab all of this and put them in there, 102 00:04:37.630 --> 00:04:39.530 we don't need this variable at all. 103 00:04:39.530 --> 00:04:41.400 So now we've got the printing of the poll options 104 00:04:41.400 --> 00:04:44.740 is Poll.get the (poll.id) access the options of it 105 00:04:44.740 --> 00:04:46.470 that goes into the database as well 106 00:04:46.470 --> 00:04:47.960 and we're printing them out. 107 00:04:47.960 --> 00:04:50.220 Now we get the option ID and the username 108 00:04:50.220 --> 00:04:51.580 that they wanna a vote for. 109 00:04:51.580 --> 00:04:56.091 And what we wanna do here is do Option.get, with (option.id) 110 00:04:56.091 --> 00:04:58.520 that's gonna give us the option that they voted for 111 00:04:58.520 --> 00:04:59.917 and we do .vote(username). 112 00:05:01.320 --> 00:05:03.200 And we no longer need this there. 113 00:05:03.200 --> 00:05:06.320 Personally I prefer this way of coding much more, 114 00:05:06.320 --> 00:05:09.550 I find it more readable, more clear what's going on 115 00:05:09.550 --> 00:05:13.530 but I understand that not everybody likes that like I do. 116 00:05:13.530 --> 00:05:15.470 So if you don't like this way of doing things, 117 00:05:15.470 --> 00:05:18.870 you prefer the databases then you can continue doing that, 118 00:05:18.870 --> 00:05:20.680 but do remember that the code is gonna get 119 00:05:20.680 --> 00:05:23.220 messier over time if you have a lot of different 120 00:05:23.220 --> 00:05:25.860 database functions all working from the same file, 121 00:05:25.860 --> 00:05:27.963 so this is a way to simplify that. 122 00:05:28.800 --> 00:05:30.740 When we're calling print_poll_options, 123 00:05:30.740 --> 00:05:33.740 we are now passing a list of options objects. 124 00:05:33.740 --> 00:05:36.720 So we should change that and reflect it in here, 125 00:05:36.720 --> 00:05:39.802 the type hinting, so we'll do List of (Option). 126 00:05:39.802 --> 00:05:43.240 Note that option here is not the option tuple in 127 00:05:43.240 --> 00:05:46.950 database.py, this is the option class that we've imported. 128 00:05:46.950 --> 00:05:49.440 So now this should not be called poll_with_options 129 00:05:49.440 --> 00:05:52.560 it should just be called options, we can iterate over them 130 00:05:52.560 --> 00:05:54.507 and now instead of (option[3]) we can do (option.id), 131 00:05:55.580 --> 00:05:58.173 to print the ID and instead of four we can .text. 132 00:06:00.370 --> 00:06:02.970 Again, you can put this inside the STr method 133 00:06:02.970 --> 00:06:04.830 of your option class if you want 134 00:06:04.830 --> 00:06:06.900 and then you can print the option directly. 135 00:06:06.900 --> 00:06:09.143 Let's go in to show_poll_votes, 136 00:06:09.143 --> 00:06:12.060 this is gonna see its biggest change 137 00:06:12.060 --> 00:06:14.310 and it's not necessarily gonna make it 138 00:06:14.310 --> 00:06:16.520 a simpler piece of code, 139 00:06:16.520 --> 00:06:18.480 but it is gonna make it a little more obvious 140 00:06:18.480 --> 00:06:21.570 what's going on in terms of the Python code. 141 00:06:21.570 --> 00:06:24.300 This is where the biggest trade-off happens 142 00:06:24.300 --> 00:06:25.620 because we have a lot of joins 143 00:06:25.620 --> 00:06:27.800 and database operations happening in the query 144 00:06:27.800 --> 00:06:29.780 and now we're gonna have them in a Python code 145 00:06:29.780 --> 00:06:31.670 which is admittedly slower, 146 00:06:31.670 --> 00:06:35.750 but the gain that we get elsewhere, I think offsets this. 147 00:06:35.750 --> 00:06:37.090 So what we were doing here is 148 00:06:37.090 --> 00:06:39.500 we were getting the poll and the votes. 149 00:06:39.500 --> 00:06:41.960 That was basically, all the things 150 00:06:41.960 --> 00:06:43.700 that we needed in order to print out. 151 00:06:43.700 --> 00:06:45.520 That gave us, even the percentage. 152 00:06:45.520 --> 00:06:47.470 We accepted on the division by zero 153 00:06:47.470 --> 00:06:49.440 to see if there were no votes cast 154 00:06:49.440 --> 00:06:51.570 and then we just went through the list 155 00:06:51.570 --> 00:06:53.770 returned and printed them out. 156 00:06:53.770 --> 00:06:57.750 Now we have to do the same thing but with our models. 157 00:06:57.750 --> 00:07:01.300 We've got a poll ID, so let's get a poll 158 00:07:01.300 --> 00:07:03.780 we need it in order to interact with the database. 159 00:07:03.780 --> 00:07:05.853 The options are poll.options. 160 00:07:06.900 --> 00:07:09.880 And the votes_per_option, we can get 161 00:07:10.750 --> 00:07:13.487 with the length of (option.votes). 162 00:07:14.910 --> 00:07:17.820 Remember, option.votes is gonna give us 163 00:07:17.820 --> 00:07:19.110 all the votes that are coming from 164 00:07:19.110 --> 00:07:22.190 the database directly for each option, 165 00:07:22.190 --> 00:07:24.530 for option in options and we're gonna 166 00:07:24.530 --> 00:07:27.070 make this into a list comprehension. 167 00:07:27.070 --> 00:07:29.710 Then the total number of votes 168 00:07:29.710 --> 00:07:31.810 is gonna be the sum of (votes_per_option). 169 00:07:32.880 --> 00:07:34.510 So now what we have here 170 00:07:34.510 --> 00:07:39.510 are three very useful variables, a list of option objects, 171 00:07:39.790 --> 00:07:43.980 for each object we have the number of votes cast 172 00:07:43.980 --> 00:07:45.440 and then we also have the total. 173 00:07:45.440 --> 00:07:47.650 So now what we wanna do is iterate 174 00:07:47.650 --> 00:07:49.470 essentially over these two at the same time 175 00:07:49.470 --> 00:07:51.540 the options and the votes_per_option. 176 00:07:51.540 --> 00:07:54.440 So that we can match them, one to the other 177 00:07:54.440 --> 00:07:57.290 the order of the elements is gonna be the same 178 00:07:57.290 --> 00:07:59.094 so the first element in this list 179 00:07:59.094 --> 00:08:01.410 is gonna be the number of votes 180 00:08:01.410 --> 00:08:03.750 for the first element in this list. 181 00:08:03.750 --> 00:08:06.546 So what we're gonna do with the try block here 182 00:08:06.546 --> 00:08:10.310 we're gonna doe for option, votes in zip 183 00:08:11.300 --> 00:08:12.850 of options and votes_per_option 184 00:08:14.850 --> 00:08:17.070 and then what we're gonna do is calculate the percentage 185 00:08:17.070 --> 00:08:19.290 that these votes are out of the total. 186 00:08:19.290 --> 00:08:24.230 So we do percentage = votes / total_votes * 100 187 00:08:24.230 --> 00:08:25.390 and then we're gonna print out. 188 00:08:25.390 --> 00:08:27.883 So we'll do (option.text) for (votes) 189 00:08:30.483 --> 00:08:32.610 or got this many votes 190 00:08:32.610 --> 00:08:35.110 and that is the percentage:.2f 191 00:08:36.410 --> 00:08:37.630 of the total. 192 00:08:37.630 --> 00:08:39.183 Then we'll except on zero division error, 193 00:08:39.183 --> 00:08:41.640 ZeroDivisionError like that 194 00:08:41.640 --> 00:08:42.550 and say 195 00:08:42.550 --> 00:08:46.620 No votes cast for this poll yet. 196 00:08:46.620 --> 00:08:48.370 A small simplification we can do here 197 00:08:48.370 --> 00:08:51.230 is we can move that over to one line, 198 00:08:51.230 --> 00:08:54.090 making sure to rename this to options. 199 00:08:54.090 --> 00:08:57.500 And now you can see that the code here 200 00:08:57.500 --> 00:09:00.080 is slightly longer 201 00:09:00.080 --> 00:09:03.190 but it is more obvious what's going on. 202 00:09:03.190 --> 00:09:05.330 We've got the options, we've got the votes per options, 203 00:09:05.330 --> 00:09:08.840 the total votes and then we calculate the percentage there. 204 00:09:08.840 --> 00:09:10.130 However, like I mentioned earlier 205 00:09:10.130 --> 00:09:12.720 it is a bit slower, a bit less efficient 206 00:09:12.720 --> 00:09:14.440 that's the trade-off that we're making. 207 00:09:14.440 --> 00:09:17.240 Finally randomising a pole winner changes slightly, 208 00:09:17.240 --> 00:09:19.130 instead of accessing the database directly 209 00:09:19.130 --> 00:09:20.450 we go through the model classes 210 00:09:20.450 --> 00:09:23.470 and instead of using order by random in a database query, 211 00:09:23.470 --> 00:09:26.010 we get all the voters and use random.choice, 212 00:09:26.010 --> 00:09:28.420 which we're gonna import in a moment. 213 00:09:28.420 --> 00:09:30.490 So here we are printing the poll options, 214 00:09:30.490 --> 00:09:32.757 all we have to do here is do (Poll.get(poll.id).options), 215 00:09:36.006 --> 00:09:38.170 and we can get rid of this. 216 00:09:38.170 --> 00:09:40.513 And then we've got the option ID that we wanna 217 00:09:40.513 --> 00:09:42.720 pick a random voter for. 218 00:09:42.720 --> 00:09:44.870 What we have to do is get the votes 219 00:09:44.870 --> 00:09:48.917 so we'll do votes = Option.get with (option.id).votes, 220 00:09:51.420 --> 00:09:55.249 and then we say winner = random.choice out of (votes) 221 00:09:55.249 --> 00:09:58.800 random.choice this is a function inside the random module 222 00:09:58.800 --> 00:10:02.400 just grabs a random element from the sequence provided. 223 00:10:02.400 --> 00:10:03.960 So here we're gonna give it the list of votes 224 00:10:03.960 --> 00:10:06.670 and it's gonna grab one of them at random. 225 00:10:06.670 --> 00:10:08.640 And then we're just gonna print 226 00:10:08.640 --> 00:10:11.270 the randomly selected winner is winner zero. 227 00:10:11.270 --> 00:10:14.020 Remember, votes is a list of tuples 228 00:10:14.020 --> 00:10:15.600 so when we do random choice of votes 229 00:10:15.600 --> 00:10:17.330 that's gonna give us a single topple. 230 00:10:17.330 --> 00:10:19.060 We're still accessing zero here 231 00:10:19.060 --> 00:10:21.890 not winner.name or something like that, 232 00:10:21.890 --> 00:10:25.060 because we don't have a model class for votes. 233 00:10:25.060 --> 00:10:27.550 Let's import the random module up here at the top 234 00:10:27.550 --> 00:10:32.470 and we can go ahead and do import random 235 00:10:32.470 --> 00:10:35.290 and we no longer need this division by zero error 236 00:10:36.380 --> 00:10:38.650 because we're using the Python division, 237 00:10:38.650 --> 00:10:41.660 We use the built in zero division error instead. 238 00:10:41.660 --> 00:10:44.520 Now I know we've made a lot of changes in this video 239 00:10:44.520 --> 00:10:45.830 and this has been a pretty long video 240 00:10:45.830 --> 00:10:48.930 so I've got a full summary of all the changes 241 00:10:48.930 --> 00:10:51.960 over in the Ebook as well as a code diff 242 00:10:51.960 --> 00:10:54.340 that you can check out that has the changes. 243 00:10:54.340 --> 00:10:57.870 Especially in apps.PY where they are the most complicated. 244 00:10:57.870 --> 00:10:59.350 So I do recommend you do that 245 00:10:59.350 --> 00:11:03.470 but am also gonna put up the code as it stands right now 246 00:11:03.470 --> 00:11:05.180 in the resources section of this lecture 247 00:11:05.180 --> 00:11:07.290 so you can download it and continue from here 248 00:11:07.290 --> 00:11:09.050 in case you have any typos or anything like that 249 00:11:09.050 --> 00:11:10.550 so you can avoid them. 250 00:11:10.550 --> 00:11:13.660 But hopefully everything we've done is clear 251 00:11:13.660 --> 00:11:16.730 and it makes sense why we're doing this. 252 00:11:16.730 --> 00:11:18.730 Again, just for the last time 253 00:11:18.730 --> 00:11:20.240 I know I've said this a few times, 254 00:11:20.240 --> 00:11:24.210 this is the trade-off between performance and efficiency 255 00:11:24.210 --> 00:11:27.480 by using custom database queries for everything 256 00:11:27.480 --> 00:11:30.710 versus simplicity and ease of maintaining 257 00:11:30.710 --> 00:11:33.180 by using the models approach. 258 00:11:33.180 --> 00:11:36.010 As applications get larger and larger, 259 00:11:36.010 --> 00:11:37.810 it starts to make more sense particularly 260 00:11:37.810 --> 00:11:39.400 if you're working with more people 261 00:11:39.400 --> 00:11:41.630 to move to a model-based approach 262 00:11:41.630 --> 00:11:43.630 since that's a bit simpler to work with. 263 00:11:44.470 --> 00:11:46.190 Thank you guys for joining in this video. 264 00:11:46.190 --> 00:11:47.370 I hope you've enjoyed it. 265 00:11:47.370 --> 00:11:50.020 Thanks for watching and I'll see you in the next one.