WEBVTT 00:00.080 --> 00:00.960 Welcome back. 00:01.200 --> 00:06.400 Now let's move to the mini project to do list application. 00:06.520 --> 00:13.040 Let's build a simple to do list application that lets the user add tasks. 00:13.200 --> 00:14.960 Show all tasks. 00:15.120 --> 00:23.120 Saves tasks to a file and uses functions, lists, files, and error handling. 00:23.160 --> 00:29.080 We're going to review all the concepts in one to do list application. 00:29.240 --> 00:33.440 At first let me start with loading task. 00:33.680 --> 00:39.840 So here let me create a new function named as load task. 00:40.000 --> 00:43.840 This function loads tasks from file. 00:43.880 --> 00:47.440 Return empty list if file doesn't exist. 00:47.520 --> 00:51.640 So here try with with open. 00:51.760 --> 00:57.220 Let me save the file as tasks dot txt file. 00:57.220 --> 01:02.300 And as I told you, we need to load the task. 01:02.500 --> 01:11.420 So I'm going to load it in reading mode as file to read the saved tasks from the tasks dot. 01:11.420 --> 01:12.660 TXT file. 01:12.660 --> 01:22.020 When the programs start, we need to use this function load task functions and we need to surround it 01:22.020 --> 01:31.500 with try and catch and true a try and accept it attempts to open this try it attempts to open the file 01:31.660 --> 01:33.820 if the file doesn't exist. 01:33.820 --> 01:39.140 For example, the first time we run the program, this operation will cause an error. 01:39.300 --> 01:43.100 Except here we need to surround it with accept. 01:43.220 --> 01:52.100 If any error occurs, like the file not existing, it simply catches the error and returns an empty 01:52.320 --> 01:53.120 list. 01:53.360 --> 01:56.280 This prevents the program from crashing. 01:56.600 --> 01:59.000 Okay, it's very simple. 01:59.040 --> 02:01.360 Now let's continue with this. 02:01.360 --> 02:08.560 Try and start with tasks equals to file dot read lines. 02:08.680 --> 02:17.120 This function reads all lines in the file and returns them as a list of strings. 02:17.160 --> 02:27.960 Okay, each task is on its own line, so this is the function that reads all lines in the file and returns 02:27.960 --> 02:30.160 them as a list of string. 02:30.520 --> 02:40.040 So this is the file tasks dot txt and we are going to get all the tasks and read them one by one. 02:40.160 --> 02:42.960 Remove the new line character. 02:43.080 --> 02:50.660 In order to remove the new line character, we need to use This return statement. 02:50.660 --> 02:59.660 So return task dot strip for task in all tasks you can, you can keep it. 02:59.660 --> 03:01.860 Don't worry, you can keep it. 03:01.900 --> 03:10.060 Also you can remove this line, but this is good for now in order not to not to to be complicated, 03:10.060 --> 03:13.540 let me continue with the project. 03:13.540 --> 03:22.340 Let me define a new function called save task and this function takes tasks as a parameter. 03:22.380 --> 03:26.380 Try with open we need to open the file. 03:26.660 --> 03:34.900 Make sure that it is similar to the name of the previously created task file, and this time we don't 03:34.900 --> 03:37.140 need to read, we need to save. 03:37.140 --> 03:43.060 So I'm going to use W as the permission okay as file. 03:43.300 --> 03:51.840 Then for every task inside tasks, we need to loop through and save it to the file. 03:51.840 --> 03:57.280 So file dot write task and the new line this thing. 03:57.320 --> 04:02.520 This is the new line in Python back slash and n. 04:02.560 --> 04:03.600 This is the new line. 04:03.640 --> 04:10.280 Now let me use except print error saving tasks. 04:10.280 --> 04:12.680 This is the save tasks function. 04:12.680 --> 04:17.480 And this is the function for loading tasks okay. 04:17.680 --> 04:25.960 This is for saving the tasks to the tasks dot txt and this is how to load the tasks dot txt file. 04:26.000 --> 04:36.640 Now let me create another function named as add tasks or add task task task equals to input. 04:36.640 --> 04:39.520 By the way, Python is very sensitive. 04:39.520 --> 04:47.690 We need to remove this space in order to solve this error and make sure trie is aligned with except. 04:47.850 --> 04:50.810 Def is aligned with def and others. 04:50.850 --> 04:52.770 Okay, so input. 04:52.810 --> 04:55.650 We need to display a message to the user. 04:55.650 --> 04:57.810 Enter a task please. 04:58.010 --> 05:06.530 Tasks dot append the task I'm using append to add it to that tasks similar to what we've done before. 05:06.650 --> 05:09.330 Okay, so we are appending. 05:09.330 --> 05:18.690 We are adding the newly created task to the end of the tasks array or list another function named as 05:18.730 --> 05:23.210 view tasks, taking to the parameters tasks. 05:23.210 --> 05:34.770 And here if tasks is true and it's not null, print your tasks and through go through all the tasks 05:34.930 --> 05:43.430 this function displays all tasks in a numbered list format, or shows a message if there are no tasks. 05:43.550 --> 05:46.310 Here we have the tasks parameter. 05:46.350 --> 05:54.070 It expects a list of tasks to display then if the tasks are not empty. 05:54.270 --> 06:03.910 If the tasks list is not empty in Python, empty lists are falsy and no empty lists are truthy. 06:04.030 --> 06:10.110 Equivalent to writing, for example, if the length of tasks greater than zero. 06:10.230 --> 06:12.630 So it's similar to this. 06:12.870 --> 06:16.750 Writing tasks greater than zero. 06:16.910 --> 06:19.310 It's similar to this. 06:19.470 --> 06:25.430 So if the tasks are not empty, go and execute this. 06:25.430 --> 06:29.270 Otherwise no tasks yet here. 06:29.310 --> 06:34.810 Print your tasks only executes if there are tasks. 06:34.850 --> 06:38.010 Prints a header for the task list. 06:38.010 --> 06:39.970 Enumerate here. 06:40.250 --> 06:41.330 Enumerate. 06:41.370 --> 06:49.290 This is the key part that tasks and one enumerate loops through the list. 06:49.290 --> 06:58.570 While keep tracking of the index, one means starting counting from one instead of the default zero. 06:58.610 --> 07:06.690 For each iteration, it gives us I the number of one, two, three, four, five, six, and others, 07:06.850 --> 07:12.050 and task the actual task in the tasks list. 07:12.050 --> 07:19.490 And here we are using the F string to format the output between I and the task. 07:19.770 --> 07:20.810 Let me run. 07:20.850 --> 07:22.730 Everything is working fine. 07:22.770 --> 07:25.930 Now we need to call those functions. 07:25.930 --> 07:28.130 So in the next video we're going to continue.