WEBVTT 1 00:00:00.080 --> 00:00:04.120 Welcome to the deep dive. Today we're diving into a 2 00:00:04.120 --> 00:00:08.359 stack of source material all about building graphical user interfaces, 3 00:00:08.759 --> 00:00:12.240 you know, those clickable windows with buttons and textboxes using Python. 4 00:00:12.359 --> 00:00:14.519 And our main guide for this journey is the second 5 00:00:14.640 --> 00:00:18.399 edition of Python gy Programming Cookbook by Burkhard A. Meyer 6 00:00:18.519 --> 00:00:19.760 from back in twenty seventeen. 7 00:00:19.800 --> 00:00:22.359 Okay, let's unpack this. This book sounds like it's basically 8 00:00:22.440 --> 00:00:25.440 a collection of recipes, right, tackling everything from just like 9 00:00:25.760 --> 00:00:28.559 getting a window to show up, yeah, to making it 10 00:00:28.600 --> 00:00:34.240 interactive with buttons, text fields, organizing complex layouts, handling data. 11 00:00:33.679 --> 00:00:36.280 Dealing with slow operations without freezing your app. That's a 12 00:00:36.280 --> 00:00:36.640 big one. 13 00:00:36.719 --> 00:00:40.479 Oh yeah, connecting to databases, even thinking about different languages 14 00:00:40.520 --> 00:00:43.320 and testing. It seems pretty comprehensive. 15 00:00:42.799 --> 00:00:46.119 It really is. It aims for a practical, hands on feel. 16 00:00:46.439 --> 00:00:50.119 The author, Burkhard Meyer, has something like seventeen years in 17 00:00:50.200 --> 00:00:53.920 the software industry, especially with Python and databases. Okay, worked 18 00:00:53.920 --> 00:00:55.880 at various places. And there was a reviewer input too 19 00:00:55.920 --> 00:00:59.079 from Mohit who also knows Python and security. So it 20 00:00:59.119 --> 00:01:02.119 feels grounded in, you know, actually building stuff, right. 21 00:01:02.399 --> 00:01:04.439 So our mission here is to sift through all these 22 00:01:04.519 --> 00:01:07.599 recipes and concepts. We want to pull out the really 23 00:01:07.719 --> 00:01:10.719 essential techniques, the key ideas, so you can get a 24 00:01:10.799 --> 00:01:15.519 solid grasp of Python gui's without reading well every single line. 25 00:01:15.319 --> 00:01:17.799 Of code, basically giving you the highlights real. 26 00:01:17.879 --> 00:01:22.000 Exactly the informed shortcut. So where does one even begin? 27 00:01:22.799 --> 00:01:26.760 The book starts like any good cookbook with the absolute minimum, right, 28 00:01:26.840 --> 00:01:28.439 getting your first window on screen? 29 00:01:28.760 --> 00:01:32.040 Yeah, using pythons built in kinter library. People usually shorten 30 00:01:32.079 --> 00:01:34.439 it to just TK. Okay, and the starting code is 31 00:01:34.599 --> 00:01:38.239 surprisingly simple. You import kinter you create an instance of 32 00:01:38.280 --> 00:01:42.000 the main window class that's TK dot TK usually assign 33 00:01:42.079 --> 00:01:45.079 it to a variable, say win, and then the absolutely 34 00:01:45.200 --> 00:01:48.319 crucial bit win dot main loop. 35 00:01:48.239 --> 00:01:50.239 The main lo Okay, that sounds fundamental. It's like the 36 00:01:50.280 --> 00:01:51.560 heart of the whole thing totally. 37 00:01:51.599 --> 00:01:53.519 It's the event loop. It just sits there, kind of 38 00:01:53.519 --> 00:01:57.719 waiting for things to happen. Button clicks, keypresses, resizing, Oh. 39 00:01:57.599 --> 00:01:58.400 The events. 40 00:01:58.519 --> 00:02:01.719 Yeah, the main loop process these. Without it, your window 41 00:02:01.799 --> 00:02:04.560 might literally just flash up and disappear because the script finishes. 42 00:02:05.079 --> 00:02:06.959 The main loop keeps it alive and listening. 43 00:02:07.200 --> 00:02:09.240 Got it. So it's not just displaying, it's running the 44 00:02:09.240 --> 00:02:12.159 interactive part. And the book mentions a quick tip about 45 00:02:12.199 --> 00:02:13.319 stopping resizing. 46 00:02:13.560 --> 00:02:16.000 Yeah, simple one. If you want to fix size window, 47 00:02:16.879 --> 00:02:20.599 just win dot resizable zero zero zero, easy way to 48 00:02:20.599 --> 00:02:21.080 lock it down. 49 00:02:21.159 --> 00:02:24.639 Okay, useful. So we have our basic window frame. But 50 00:02:24.840 --> 00:02:26.960 an empty box isn't much of a GUI. You need 51 00:02:26.960 --> 00:02:29.960 stuff inside it. The widgets. What are the first building 52 00:02:30.000 --> 00:02:31.439 blocks the book introduces. 53 00:02:31.680 --> 00:02:35.360 Well, the most basic are probably labels. Just text for 54 00:02:35.439 --> 00:02:39.080 showing information or instructions uses TTK dot label simple text. 55 00:02:39.360 --> 00:02:42.639 Then entry widgets. Those are your standard single line textboxes 56 00:02:42.680 --> 00:02:45.360 for getting user input dtk dot. 57 00:02:45.280 --> 00:02:48.599 Entry right displaying info versus getting input. And the main 58 00:02:48.639 --> 00:02:49.639 way to trigger. 59 00:02:49.319 --> 00:02:52.080 Actions buttons dot ttk dot button. And this is where 60 00:02:52.120 --> 00:02:55.039 callbacks become super important. When you create a button, you 61 00:02:55.080 --> 00:02:57.240 tell it which Python function to call when it's clicked 62 00:02:58.039 --> 00:03:00.960 using the command argument. So you'd have my function name 63 00:03:01.400 --> 00:03:03.759 that links the click event to your code. 64 00:03:03.840 --> 00:03:06.479 So the click is the event command links it to 65 00:03:06.520 --> 00:03:08.159 the callback function precisely. 66 00:03:08.879 --> 00:03:12.439 That function just waits passively until the main loop detects 67 00:03:12.439 --> 00:03:14.879 a click on that button, and then it gets executed. 68 00:03:15.120 --> 00:03:19.039 Nice. The book also mentions usability things like putting the 69 00:03:19.080 --> 00:03:21.680 cursor in the right place automatically YEP. 70 00:03:21.680 --> 00:03:24.159 Using the focus method on a widget. So if you 71 00:03:24.199 --> 00:03:27.520 call my entry dot focus, the cursor starts blinking in 72 00:03:27.560 --> 00:03:29.719 that text box. Little things like that make a. 73 00:03:29.680 --> 00:03:31.199 Difference and disabling widgets. 74 00:03:31.479 --> 00:03:33.319 Yeah, you can set a property when you create it, 75 00:03:33.400 --> 00:03:35.960 like a button, so it appears grayed out and doesn't 76 00:03:36.000 --> 00:03:36.879 respond to clicks. 77 00:03:37.159 --> 00:03:41.879 Okay, what about giving users choices not just text entry? Uh? 78 00:03:42.000 --> 00:03:44.879 Check buttons are covered for simple on off choices like 79 00:03:44.960 --> 00:03:48.240 a settings toggle right. They hold their state checked or unchecked, 80 00:03:48.319 --> 00:03:52.120 usually zero or one using a special variable pickenter dot infar. 81 00:03:52.840 --> 00:03:56.159 You can set the initial state using select an alignment. 82 00:03:56.360 --> 00:03:57.639 You mentioned sticky before. 83 00:03:57.840 --> 00:04:01.199 Yes, sticky tk wf and gets used with check buttons 84 00:04:01.199 --> 00:04:02.759 to make sure they line up nicely on the left 85 00:04:02.800 --> 00:04:04.960 side within their layout. Cell w for. 86 00:04:05.039 --> 00:04:08.039 West got it, and radio buttons if for picking just 87 00:04:08.080 --> 00:04:09.479 one option from a group. 88 00:04:09.560 --> 00:04:13.039 Exactly radio buttons. The key difference is that a group 89 00:04:13.080 --> 00:04:16.560 of radio buttons all share the same kintervariable. When you 90 00:04:16.600 --> 00:04:19.720 click one, its value gets assigned to that variable, and 91 00:04:19.759 --> 00:04:22.279 the others automatically de select ah. 92 00:04:22.399 --> 00:04:25.560 So check buttons each have their own variable. Radio buttons 93 00:04:25.639 --> 00:04:26.279 share one. 94 00:04:26.759 --> 00:04:30.639 That's the crucial distinction for managing their state and selecting 95 00:04:30.639 --> 00:04:34.000 A radio button can also trigger a callback immediately, maybe 96 00:04:34.040 --> 00:04:36.519 to change something else in the GI based on the choice. 97 00:04:36.600 --> 00:04:39.680 Okay, what about selecting numbers or from a list? 98 00:04:39.879 --> 00:04:41.839 Spin box controls are good for that. You get a 99 00:04:41.839 --> 00:04:44.480 little box with up down arrows. Again, cycle through numbers 100 00:04:44.600 --> 00:04:46.680 or even a predefined list of text items. 101 00:04:46.759 --> 00:04:48.519 Can you react when the value changes? 102 00:04:48.600 --> 00:04:50.439 Oh yeah, just like a button, You can attach a 103 00:04:50.439 --> 00:04:53.560 command callback that fires whenever the stin box value is changed. 104 00:04:54.120 --> 00:04:56.920 The book shows an example of displaying the selected value 105 00:04:57.360 --> 00:04:59.600 in say a larger text area. 106 00:05:00.120 --> 00:05:02.639 Larger text area scroll texts exactly. 107 00:05:02.879 --> 00:05:06.680 Scroll text really useful for multiline input or display. The 108 00:05:06.759 --> 00:05:09.920 nice thing is features like word wrapping, wrap ek at 109 00:05:10.000 --> 00:05:13.639 word and the scroll bars appearing automatically. They just work. 110 00:05:14.000 --> 00:05:15.959 You mainly just defined its width and height. 111 00:05:16.160 --> 00:05:20.560 Okay, so we can populate a window with widgets, but 112 00:05:20.600 --> 00:05:22.800 they'll just pile up, right, How do you organize them? 113 00:05:23.120 --> 00:05:24.000 Layout management? 114 00:05:24.120 --> 00:05:28.160 Yeah, that's the next big step arranging things logically. The 115 00:05:28.199 --> 00:05:32.199 core idea the book uses is nesting. You put widgets 116 00:05:32.319 --> 00:05:33.399 inside container. 117 00:05:33.439 --> 00:05:36.879 Fidgets like containers within container pretty much. 118 00:05:37.079 --> 00:05:39.720 Ttk dot label frame is a key example. It's a 119 00:05:39.759 --> 00:05:42.319 container that draws a border around its contents and has 120 00:05:42.360 --> 00:05:45.920 a text label. You put related widgets inside a label frame. 121 00:05:46.399 --> 00:05:48.839 Then you arrange the label frame itself within the main window, 122 00:05:49.240 --> 00:05:52.160 maybe alongside other label frames or widgets. It helps break 123 00:05:52.199 --> 00:05:53.519 down complexity. 124 00:05:53.040 --> 00:05:55.399 And spacing to avoid everything being crammed together. 125 00:05:55.560 --> 00:05:59.040 Patting pad X for horizontal space, patty for vertical space 126 00:05:59.040 --> 00:06:01.319 around each widget. Usually set these when you place the 127 00:06:01.319 --> 00:06:02.720 widget using the layout manager. 128 00:06:02.800 --> 00:06:05.120 The book mentions grid mostly Yes. 129 00:06:05.240 --> 00:06:08.680 The grid layout manager is heavily featured. It arranges widgets 130 00:06:08.720 --> 00:06:12.000 in well a grid of rows and columns. You specify 131 00:06:12.040 --> 00:06:13.800 the row and column for each widget. 132 00:06:13.480 --> 00:06:14.959 And you can tweak padding later too. 133 00:06:15.319 --> 00:06:17.560 The book points out you can use methods like grid 134 00:06:17.600 --> 00:06:20.879 Configure after placing a widget to adjust its padding or 135 00:06:20.920 --> 00:06:22.279 other grid options if needed. 136 00:06:22.480 --> 00:06:25.639 What about when the user resizes the window. Do widgets 137 00:06:25.680 --> 00:06:27.920 just stay fixed or can they stretch. 138 00:06:27.680 --> 00:06:30.920 Ah dynamic expansion. That's where Sticky really comes into play again. 139 00:06:31.000 --> 00:06:34.040 We saw sticky tk dot W for left alignment, but 140 00:06:34.120 --> 00:06:37.160 you can use tk E eastwright, TK in north top, 141 00:06:37.319 --> 00:06:41.480 tks self bottom or combinations like TK dot n SEW 142 00:06:41.839 --> 00:06:44.680 to make a widget stretch and fill the entire grid cell. 143 00:06:44.720 --> 00:06:47.360 It's in horizontally and vertically as the window. 144 00:06:47.079 --> 00:06:48.839 Resizes and spanning multiple cells. 145 00:06:48.920 --> 00:06:51.759 Also crucial, column span two makes a widget take up 146 00:06:51.759 --> 00:06:55.560 two columns. Rospan three takes three rows, combining sicki and columns. 147 00:06:55.600 --> 00:06:58.399 Thin row span gives you really fine grain control over 148 00:06:58.439 --> 00:06:59.600 how your layout adapts. 149 00:07:00.040 --> 00:07:02.560 Grid is the main tool here. What if the GUI 150 00:07:02.759 --> 00:07:05.720 has like tons of options, does it just become one 151 00:07:05.759 --> 00:07:06.480 giant window. 152 00:07:06.680 --> 00:07:09.920 That's where TTK dot notebook comes in. It creates tabbed interfaces. 153 00:07:09.920 --> 00:07:12.480 You put different sets of controls on different tabs, keeps 154 00:07:12.480 --> 00:07:14.160 the main window much cleaner tabs. 155 00:07:14.199 --> 00:07:18.160 Okay, that makes sense for complexity. Moving beyond structure, what 156 00:07:18.240 --> 00:07:21.399 about the look and feel, making it polished? Giving feedback? 157 00:07:21.839 --> 00:07:25.480 Right? Standard pop up messages are a basic need. Kinder 158 00:07:25.480 --> 00:07:29.120 has built in message box functions show info for infos, 159 00:07:29.160 --> 00:07:31.000 show warning for warnings, shower for. 160 00:07:31.079 --> 00:07:33.839 Errors, and they pause the main GUI. 161 00:07:34.120 --> 00:07:37.040 Yes, they're modal. The user has to dismiss the message 162 00:07:37.040 --> 00:07:39.519 box before they can interact with the main window. Again 163 00:07:40.120 --> 00:07:41.040 important behavior. 164 00:07:41.240 --> 00:07:44.800 The book mentions independent message boxes. What's that about. 165 00:07:44.920 --> 00:07:47.680 It's more about maybe structuring your code so the call 166 00:07:47.839 --> 00:07:50.079 to show a message box is in its own function, 167 00:07:50.480 --> 00:07:53.519 perhaps for reuse. There's a small code trick mention to 168 00:07:53.560 --> 00:07:55.720 get the text into the body, not the title. And 169 00:07:55.759 --> 00:07:58.639 also a reminder if you create a tk instance just 170 00:07:58.680 --> 00:08:01.519 to use a message box, might need wind dot withdraw 171 00:08:01.800 --> 00:08:04.160 to hide the blank extra window that kinder. 172 00:08:03.959 --> 00:08:07.240 Creates little details. What about customizing the main window itself 173 00:08:07.360 --> 00:08:09.000 title icon pzps. 174 00:08:09.360 --> 00:08:11.319 Setting the title is just a method call wind dot 175 00:08:11.360 --> 00:08:14.399 title my app. The icon usually needs a specific file 176 00:08:14.439 --> 00:08:17.240 format dot ico on Windows, and you might need the 177 00:08:17.279 --> 00:08:18.319 full paths to the file. 178 00:08:18.439 --> 00:08:22.279 Any other visual tweaks mentioned like three D effects, Yeah. 179 00:08:22.120 --> 00:08:25.399 The relief property comes up again. Setting relief sunken or 180 00:08:25.439 --> 00:08:28.600 relief raised on widgets like frames or labels can give 181 00:08:28.639 --> 00:08:31.959 them that classic embossed or debossed look adds a bit 182 00:08:32.000 --> 00:08:32.639 of depth. 183 00:08:32.480 --> 00:08:35.039 And those little helper texts when you hover over something. 184 00:08:35.279 --> 00:08:38.519 Tooltips, Yeah, the book shows how to implement them. It 185 00:08:38.559 --> 00:08:42.240 actually suggests using an object oriented approach creating a tooltip 186 00:08:42.279 --> 00:08:46.360 class ahop again Yeah, it makes the tooltip logic reusable 187 00:08:46.399 --> 00:08:48.320 and cleaner to attach to different widgets. 188 00:08:48.440 --> 00:08:52.399 Okay, And for tasks that take a while showing progress. 189 00:08:52.080 --> 00:08:54.960 The standard TTK dot progress bar you add it to 190 00:08:55.000 --> 00:08:57.320 your layout and the book shows how to start its 191 00:08:57.360 --> 00:09:00.600 animation when a task begins and stop it when done, 192 00:09:01.159 --> 00:09:03.200 basic visual feedback that something's happening. 193 00:09:03.240 --> 00:09:06.279 This feels like a natural lead into handling data within 194 00:09:06.320 --> 00:09:10.240 the dui and maybe where OP really starts to shine definitely. 195 00:09:10.559 --> 00:09:14.200 First, the book introduces special tinter variable types like stringvar. 196 00:09:14.480 --> 00:09:16.519 These aren't just normal Python strings. 197 00:09:16.120 --> 00:09:16.919 How are they different? 198 00:09:17.000 --> 00:09:19.960 They're designed to be linked directly to widgets. If you 199 00:09:20.039 --> 00:09:23.000 link a stringvar to an entry widget, changing the string 200 00:09:23.120 --> 00:09:25.720 bar in your code automatically updates the text in the 201 00:09:25.840 --> 00:09:29.240 entry box, and typing in the entry box updates the stringvar. 202 00:09:29.440 --> 00:09:31.639 Oh two way binding kind of yeah. 203 00:09:31.879 --> 00:09:34.080 Use methods like dot set to put a value into 204 00:09:34.120 --> 00:09:36.919 the string bar and dot get to recrieve the current 205 00:09:37.039 --> 00:09:37.679 value from it. 206 00:09:37.879 --> 00:09:39.879 And the book notes a quirk about needing a TK 207 00:09:39.960 --> 00:09:42.639 instance even just to create a string bar, even if 208 00:09:42.639 --> 00:09:43.440 you hide the window. 209 00:09:43.960 --> 00:09:46.679 Yeah, it's a bit weird. These ticket tenor variables rely 210 00:09:46.799 --> 00:09:50.480 on the underlying TK machinery being initialized, which happens when 211 00:09:50.519 --> 00:09:53.480 you create TK. So even for non visual use, you 212 00:09:53.519 --> 00:09:57.240 might need root ektktk root dot withdrawal. 213 00:09:57.600 --> 00:10:00.399 So calling dot get on these variables or directly on 214 00:10:00.399 --> 00:10:02.960 a widgets like entry is how you pull the user's 215 00:10:03.039 --> 00:10:05.360 input back into your Python logic. 216 00:10:05.559 --> 00:10:07.879 That's the main way. Once you get the value, it's 217 00:10:07.919 --> 00:10:11.399 just a standard Python string or number or whatever, and 218 00:10:11.440 --> 00:10:12.960 you can work with it. The trick is when to 219 00:10:13.000 --> 00:10:15.279 call dot get, usually inside a callbad function. 220 00:10:15.600 --> 00:10:19.120 The book mentions using module level global variables for simple 221 00:10:19.200 --> 00:10:22.519 data sharing, but then pushes towards op pretty strongly. 222 00:10:22.879 --> 00:10:26.559 Why well, globals are tempting for super simple scripts, quick 223 00:10:26.600 --> 00:10:29.279 and easy, but as soon as your GUI gets even 224 00:10:29.440 --> 00:10:33.240 a little bit complex, tracking which function modified which global 225 00:10:33.320 --> 00:10:37.120 variable becomes a nightmare, really hard to debug OPI. Using 226 00:10:37.120 --> 00:10:41.440 classes provides encapsulation. You bundle the data as attributes of 227 00:10:41.480 --> 00:10:44.840 an object, together with the methods functions belonging to the 228 00:10:44.840 --> 00:10:48.159 object that operate on that data. It keeps things organized, 229 00:10:48.240 --> 00:10:51.960 prevents accidental modification from unrelated code, and makes the whole 230 00:10:51.960 --> 00:10:54.039 thing much easier to maintain and extend later. 231 00:10:54.159 --> 00:10:56.360 So a method is just a function inside a class 232 00:10:56.360 --> 00:10:57.879 that acts on the classes data. 233 00:10:57.679 --> 00:11:00.919 Pretty much, and it usually takes self as it's first argument, 234 00:11:01.120 --> 00:11:03.960 which refers to the specific object instance it's working with. 235 00:11:04.360 --> 00:11:08.480 The book really emphasizes trying to refactor a messy NONOOPI 236 00:11:08.600 --> 00:11:12.919 procedural GUI into oop later is painful. It's much better 237 00:11:12.960 --> 00:11:14.919 to start with an OP structure if your project is 238 00:11:14.960 --> 00:11:16.559 going to be anything beyond trivial. 239 00:11:16.240 --> 00:11:18.279 And this connects back to the event driven nature. 240 00:11:18.600 --> 00:11:22.440 Absolutely, the GUI sits there, an event happens button click, 241 00:11:23.039 --> 00:11:26.000 the main loop directs it to the callback. That callback 242 00:11:26.039 --> 00:11:28.720 is often an OP method self dot on button click, 243 00:11:29.080 --> 00:11:31.919 which then uses self to access the object's data, maybe 244 00:11:31.960 --> 00:11:35.279 calls dot get on some widgets, does calculations, and maybe 245 00:11:35.279 --> 00:11:38.000 calls dot set on other widgets to update the display. 246 00:11:38.120 --> 00:11:40.159 Okay, this next one is where I think a lot 247 00:11:40.200 --> 00:11:43.720 of people, including me, have hit a wall. Initially, you 248 00:11:43.759 --> 00:11:46.159 click a button that app needs to do something slow, 249 00:11:46.200 --> 00:11:48.759 and the whole GUI just freezes. 250 00:11:48.919 --> 00:11:53.440 Ah. Yes, the dreaded unresponsive GUI. It's a classic symptom 251 00:11:53.480 --> 00:11:56.320 of doing long running tasks directly in the main GUI thread. 252 00:11:56.360 --> 00:11:59.519 Why does it happen because basic kinter and many GI 253 00:11:59.559 --> 00:12:02.519 toolkits runs its event loop main loop in a single thread. 254 00:12:02.919 --> 00:12:05.279 If that thread gets busy doing something else like downloading 255 00:12:05.279 --> 00:12:08.960 a big file, running a complex calculation, querying a slow database, 256 00:12:09.200 --> 00:12:11.840 it can't process other events. It can't redraw the window, 257 00:12:12.000 --> 00:12:14.000 respond to clicks anything. It's blocked. 258 00:12:14.639 --> 00:12:15.480 So what's the fix? 259 00:12:15.919 --> 00:12:19.240 Multi threading? You need to run that long running task 260 00:12:19.399 --> 00:12:22.480 in a separate thread. The main thread stays free to 261 00:12:22.559 --> 00:12:25.639 run the main loop and keep the GI responsive while 262 00:12:25.639 --> 00:12:28.039 the worker thread chugs away in the background. 263 00:12:28.240 --> 00:12:31.759 Okay, threads. The book distinguishes between threads and processes. 264 00:12:31.840 --> 00:12:36.000 Briefly, Yes, Processes are more isolated, each with its own memory. 265 00:12:36.399 --> 00:12:39.559 Threads run within the same process and share memory. For 266 00:12:39.679 --> 00:12:43.159 tasks within a single GUI application that need to communicate 267 00:12:43.200 --> 00:12:46.320 back to the GUI, threads are often simpler because sharing 268 00:12:46.399 --> 00:12:47.320 data is easier. 269 00:12:47.679 --> 00:12:51.039 Can that worker thread directly update a techer and widget 270 00:12:51.120 --> 00:12:52.960 like change a labels text when it's done? 271 00:12:53.480 --> 00:12:57.240 Generally No, that's not thread safe. Directly manipulating taker widgets 272 00:12:57.240 --> 00:13:00.399 from a background thread can cause crashes or weird behavior. 273 00:13:00.559 --> 00:13:03.200 So how does the worker thread tell the main GUI thread, Hey, 274 00:13:03.360 --> 00:13:04.720 I'm done, here's the result. 275 00:13:04.840 --> 00:13:08.879 The standard safeway is using Python's q Q. It's a 276 00:13:08.960 --> 00:13:12.159 data structure specifically designed for thread safe communication. 277 00:13:12.320 --> 00:13:14.759 A que like a waiting line exactly. 278 00:13:15.000 --> 00:13:18.600 The worker thread puts its result onto the que mi 279 00:13:18.799 --> 00:13:23.360 que dot dwizzled. The main GUI thread meanwhile periodically checks 280 00:13:23.399 --> 00:13:26.440 the queue mi qu dot get no weight. If there's 281 00:13:26.440 --> 00:13:29.279 something there, it safely pulls the result off and updates 282 00:13:29.320 --> 00:13:30.799 the GUI widgets from within the. 283 00:13:30.720 --> 00:13:33.279 Main thread, so the Q acts as a safe ordered 284 00:13:33.279 --> 00:13:34.600 mailbox between threads. 285 00:13:34.799 --> 00:13:39.320 Perfect analogy. It decouples the threads FIFO first in, first 286 00:13:39.320 --> 00:13:42.519 out means results are typically processed in the order they finish. 287 00:13:42.919 --> 00:13:45.159 The book shows how you can pass a Q object around, 288 00:13:45.399 --> 00:13:47.799 letting different parts of your code, even in separate modules, 289 00:13:48.000 --> 00:13:50.440 feed results back to the GUI thread without freezing it. 290 00:13:50.559 --> 00:13:53.519 And common examples of slow tasks shown are things like 291 00:13:53.559 --> 00:13:55.360 file operations or network calls. 292 00:13:55.639 --> 00:13:58.679 Yes, using kinter dot request dot a filename is quick, 293 00:13:58.960 --> 00:14:02.519 but actually reading or writing a large file could block. Similarly, 294 00:14:02.600 --> 00:14:05.639 using erallib dot request dot eurolopin to fetch web data 295 00:14:05.879 --> 00:14:08.120 definitely needs a thread if the network is slow where 296 00:14:08.159 --> 00:14:11.080 the download is large. The book also stresses using try 297 00:14:11.159 --> 00:14:14.200 except blocks around network code to handle potential errors. 298 00:14:14.000 --> 00:14:17.720 Gracefully makes sense okay, shifting gears to data persistence. The 299 00:14:17.720 --> 00:14:21.519 book dives into connecting to my SQL databases, specifically. 300 00:14:21.159 --> 00:14:24.440 Right, a very common requirement. It uses the miceql dot 301 00:14:24.519 --> 00:14:27.840 connector library, which is the official driver from Oracle. 302 00:14:27.480 --> 00:14:31.080 My school, and the first warning is about security absolutely critical. 303 00:14:31.159 --> 00:14:35.519 The book hammers this home do not put your database 304 00:14:35.879 --> 00:14:39.320 username and password directly in your Python source code. It's 305 00:14:39.360 --> 00:14:42.279 a huge security risk if that code ever gets shared 306 00:14:42.360 --> 00:14:42.919 or exposed. 307 00:14:43.000 --> 00:14:43.720 So what should you do? 308 00:14:44.279 --> 00:14:47.600 Store credential separately? Maybe in a configuration file that's kept 309 00:14:47.639 --> 00:14:50.720 in a secure location, has restricted permissions and is read 310 00:14:50.720 --> 00:14:54.159 by your application at runtime, or use environment variables or 311 00:14:54.200 --> 00:14:57.240 a secrets management system, just not hard coded. 312 00:14:57.360 --> 00:14:59.960 Okay, what basic database operations does it cover? 313 00:15:00.320 --> 00:15:04.360 The core crwould operations select to fetch data, insert to 314 00:15:04.399 --> 00:15:08.320 add rows, update to change existing rows, delete to remove rows. 315 00:15:08.559 --> 00:15:12.080 It also briefly introduces essential database concepts like primary keys, 316 00:15:12.200 --> 00:15:16.080 unique IDs for rows and foreign keys, linking related tables. 317 00:15:16.320 --> 00:15:18.600 And is there a tool mentioned for working with the 318 00:15:18.679 --> 00:15:20.080 database outside of Python. 319 00:15:20.440 --> 00:15:23.879 Yeah, myseql workbench. It's a free GI tool provided by 320 00:15:23.879 --> 00:15:28.440 myseql itself, really helpful during development for designing your database schema, 321 00:15:28.759 --> 00:15:32.200 running test SQL queries, checking data without needing to build 322 00:15:32.240 --> 00:15:33.399 all that into your Python app. 323 00:15:33.440 --> 00:15:36.559 First, Okay, let's talk about making apps for a global audience. 324 00:15:36.799 --> 00:15:40.879 Internationalization and localization I eighteen N and L ten N right. 325 00:15:41.000 --> 00:15:44.679 Internationalization I eighteen N I plus eighteen letters plus N 326 00:15:45.159 --> 00:15:47.440 is about designing your app so it can be adapted. 327 00:15:47.840 --> 00:15:51.200 The main part is separating all user visible text labels, 328 00:15:51.240 --> 00:15:53.759 button text messages from your code logic. How do you 329 00:15:53.840 --> 00:15:56.240 do that? The book shows using a simple Python class 330 00:15:56.320 --> 00:15:59.320 is a I eighteen n that holds dictionaries of strings 331 00:15:59.320 --> 00:16:02.159 for different language maybe self dot strings and like you 332 00:16:02.200 --> 00:16:05.039 think kell okay, then in your guy code instead of 333 00:16:05.080 --> 00:16:07.879 tdk dot label to ttk dot label ticks self dot 334 00:16:07.919 --> 00:16:09.960 I t and n dot gets string, gets string greeting 335 00:16:10.240 --> 00:16:12.919 by changing which language dictionary the I eighten n object 336 00:16:13.000 --> 00:16:15.360 uses eg self dot I ten n dot I ten 337 00:16:15.480 --> 00:16:18.279 nd low the whole GUI can switch language. 338 00:16:18.320 --> 00:16:21.279 That's clever and localization L ten N. That's more than 339 00:16:21.320 --> 00:16:22.000 just language. 340 00:16:22.159 --> 00:16:25.000 Yeah, L ten N L plus ten letters plus n 341 00:16:25.360 --> 00:16:28.799 is the actual adaptation to a specific locale. It includes 342 00:16:28.840 --> 00:16:31.240 things like date time formats M and D d y 343 00:16:31.399 --> 00:16:34.919 y versus D M M y y, currency symbols, number 344 00:16:34.960 --> 00:16:38.799 formatting using commas or periods as decimal separators, and crucially, 345 00:16:39.200 --> 00:16:39.960 time zones. 346 00:16:40.440 --> 00:16:42.000 Time zones sound tricky. 347 00:16:41.759 --> 00:16:44.399 They can be. The book shows using pythons built in 348 00:16:44.519 --> 00:16:47.720 DateTime module along with the third party pits library to 349 00:16:47.799 --> 00:16:51.960 handle time zone conversions correctly, like displaying a time recorded 350 00:16:52.000 --> 00:16:54.679 in UTC for someone in say Pacific time. 351 00:16:54.919 --> 00:16:58.960 What about displaying characters from other languages like German, Lauts 352 00:16:59.080 --> 00:17:00.519 or maybe Asians. 353 00:17:00.720 --> 00:17:03.799 Unicode handling Python three is generally pretty good with Unicode strings, 354 00:17:03.960 --> 00:17:07.480 but sometimes, depending on your operating system, terminal or IDE settings, 355 00:17:07.759 --> 00:17:11.079 you might run into encoding issues where characters display incorrectly. 356 00:17:11.160 --> 00:17:12.839 Any solutions mentioned using. 357 00:17:12.599 --> 00:17:15.359 Python's direct Unicode escapes like U TOFC for you can 358 00:17:15.400 --> 00:17:18.680 be a robust way, or more commonly, ensuring your source 359 00:17:18.680 --> 00:17:21.440 code files are saved with UTF eight encoding and that 360 00:17:21.480 --> 00:17:24.359 your development environment like pit of eclip settings mentioned in 361 00:17:24.400 --> 00:17:27.079 the book is configured to handle UTFA correctly. 362 00:17:27.279 --> 00:17:29.599 Okay, building all this is great, but it needs to 363 00:17:29.599 --> 00:17:34.960 work reliably. Testing. How does the book approach ensuring quality? 364 00:17:35.599 --> 00:17:38.680 It emphasizes that testing isn't just one thing. It happens 365 00:17:38.680 --> 00:17:41.960 at multiple levels. There's developer testing just running the code. 366 00:17:41.960 --> 00:17:46.440 Maybe the IDE catches syntax errors using source control like GIT, 367 00:17:46.599 --> 00:17:50.640 which helps catch integration conflicts, API testing testing the non 368 00:17:50.680 --> 00:17:54.480 GUI logic, integration testing, making sure different parts work together, 369 00:17:54.759 --> 00:17:56.440 and finally end user testing. 370 00:17:56.640 --> 00:17:58.200 All catch in different kinds of bugs. 371 00:17:58.279 --> 00:18:01.880 Exactly, you need a mix for debugging when things go 372 00:18:01.960 --> 00:18:05.200 wrong during development. Buggers, Yeah, using your IDEs debugger is 373 00:18:05.279 --> 00:18:08.640 key setting break points to pause the code, inspecting the 374 00:18:08.680 --> 00:18:11.640 values of variables at that point using watches stepping through 375 00:18:11.640 --> 00:18:14.400 code line by line. The book notes that in GUIs 376 00:18:14.440 --> 00:18:17.279 you often want to put break points inside your event 377 00:18:17.319 --> 00:18:20.720 handler functions like button callbacks, because that's where the action 378 00:18:20.799 --> 00:18:24.519 happens after the mainloop dispatches an event. It also suggests 379 00:18:24.559 --> 00:18:28.079 setting up your own simple logging using Python's logging module. 380 00:18:28.279 --> 00:18:30.480 May be configured in the if name equals main part 381 00:18:30.519 --> 00:18:31.119 of your script. 382 00:18:31.240 --> 00:18:32.279 Why custom logging. 383 00:18:32.400 --> 00:18:35.000 It gives you more control than just print statements. You 384 00:18:35.039 --> 00:18:39.480 can set different logging levels, debug info, warning, error, easily 385 00:18:39.480 --> 00:18:42.319 switch between logging to the console or a file, and 386 00:18:42.400 --> 00:18:45.880 filter messages. It's great for tracing what your application is doing, 387 00:18:46.200 --> 00:18:48.079 especially in response to events. 388 00:18:47.759 --> 00:18:49.880 And for more formal automated tests. 389 00:18:50.319 --> 00:18:54.079 Python's built in unitist framework is the standard shown. The 390 00:18:54.160 --> 00:18:57.039 idea is to write separate test code that imports your 391 00:18:57.039 --> 00:18:59.640 application code and verifies its behavior. 392 00:19:00.039 --> 00:19:00.599 Does that work? 393 00:19:00.799 --> 00:19:03.880 You create test classes inheriting from unitist dot test case. 394 00:19:04.559 --> 00:19:07.839 Inside you write methods whose names start with test. Within 395 00:19:07.880 --> 00:19:10.440 these methods, you call parts of your application code and 396 00:19:10.599 --> 00:19:14.519 use assertion methods like self dot assert equal actual expected 397 00:19:14.880 --> 00:19:16.240 to check if the results are correct. 398 00:19:16.319 --> 00:19:19.200 But how do you test gy interactions with unitist. You 399 00:19:19.240 --> 00:19:21.720 can't easily click a button in a test script. 400 00:19:21.680 --> 00:19:24.960 Right, You usually don't simulate the physical click. Instead, you 401 00:19:25.039 --> 00:19:28.440