1 00:00:00,210 --> 00:00:05,890 I hope you've given that a good go and now I'm going to run through the solution with you. Here, 2 00:00:05,910 --> 00:00:12,660 I've got those three links open and they're all documentation on W3schools for different methods 3 00:00:12,660 --> 00:00:13,470 in Python. 4 00:00:13,980 --> 00:00:17,010 The first one is a method called readlines. 5 00:00:17,340 --> 00:00:19,050 It's really important that you have that 6 00:00:19,050 --> 00:00:23,250 's' because there's also another method called readline, the singular form. 7 00:00:23,760 --> 00:00:31,770 What readlines does is it returns all the lines in the file as a list where each line is an item in 8 00:00:31,770 --> 00:00:32,700 the list object. 9 00:00:33,150 --> 00:00:40,680 For example, we can run this example and you can see that inside this demo file, readlines, there's 10 00:00:40,680 --> 00:00:49,800 several lines in that file, and each line after running this method, gets added as a item inside a list 11 00:00:50,190 --> 00:00:51,210 like this. 12 00:00:52,170 --> 00:00:57,450 Now, the next method I showed you is the python string replace method. 13 00:00:58,050 --> 00:01:04,080 And what this method does is it will replace a specified phrase with another specified phrase. 14 00:01:04,500 --> 00:01:10,410 If the starting text was 'I like bananas' and you do txt.replace, you can replace the part where 15 00:01:10,410 --> 00:01:12,180 it says bananas with apples. 16 00:01:12,480 --> 00:01:18,150 And when you print, you can see the end outcome changes that text to I like apples. 17 00:01:18,930 --> 00:01:23,430 Now, the final method that I showed you is the string strip method. 18 00:01:23,760 --> 00:01:29,720 And what this does is it will remove the spaces at the beginning and at the end of the string. 19 00:01:30,030 --> 00:01:35,340 So if our starting text has a lot of whitespace at the beginning and the end, and then we do txt. 20 00:01:35,490 --> 00:01:41,440 strip, it'll get rid of all of that extra space and it ends up with just the word. 21 00:01:41,940 --> 00:01:45,360 Now, if you have a space in between, another word 22 00:01:47,850 --> 00:01:54,420 like this, if we hit run, then you can see that it keeps the space in between the words, but it gets 23 00:01:54,420 --> 00:01:59,280 rid of any spaces on either side, which is really, really handy. 24 00:01:59,730 --> 00:02:03,370 And you're going to see hopefully why it's really, really useful. 25 00:02:03,960 --> 00:02:10,710 So now that we've reviewed these three methods that we haven't seen before, and normally you would probably 26 00:02:10,710 --> 00:02:14,670 find these when you actually get stuck and when you're searching Stack Overflow. 27 00:02:15,480 --> 00:02:22,150 But now that you're aware of those methods, let's go ahead and create a letter using our starting letter. 28 00:02:22,440 --> 00:02:25,170 So I'm going to go ahead and delete everything in here. 29 00:02:25,560 --> 00:02:28,880 And now let's go ahead and tackle this challenge. 30 00:02:29,220 --> 00:02:33,720 So the first thing I want to do is to get hold of all of the invited names 31 00:02:33,930 --> 00:02:36,780 and I want to turn them into a list. Now 32 00:02:36,780 --> 00:02:43,590 I can, of course, rather tediously go and add some square brackets, add some quotation marks around 33 00:02:43,590 --> 00:02:46,400 it, and then add it into my main.py. 34 00:02:46,830 --> 00:02:48,120 But I don't want to do that. 35 00:02:48,460 --> 00:02:51,320 Instead, I'm going to get Python to read the file. 36 00:02:51,690 --> 00:02:57,210 So using our classic syntax with open, I'm going to open up that file. 37 00:02:57,690 --> 00:03:03,870 But in order to open it up, I need to specify a string which is going to be the path that leads me 38 00:03:04,020 --> 00:03:06,160 from here to here. 39 00:03:06,660 --> 00:03:08,880 So let's think about how we might get there. 40 00:03:09,210 --> 00:03:16,350 Now, this input output folder is on the same hierarchical level as our current file where we're writing 41 00:03:16,350 --> 00:03:16,980 our code. 42 00:03:17,550 --> 00:03:24,240 If we want to use a relative file path, we can simply say go into the current folder which is mail- 43 00:03:24,240 --> 00:03:28,410 merge-project-start and then find a folder called Input. 44 00:03:29,730 --> 00:03:31,700 Inside this folder called Input, 45 00:03:31,740 --> 00:03:35,430 we're going to go to another folder called Names. 46 00:03:36,120 --> 00:03:41,640 And then inside that folder of names, we're going to get a hold of that file called invited_names 47 00:03:41,640 --> 00:03:42,360 .txt. 48 00:03:42,780 --> 00:03:46,980 And PyCharm is super clever and it helps you out with a lot of typing. 49 00:03:47,250 --> 00:03:48,810 So it saves you some time as well. 50 00:03:49,380 --> 00:03:52,260 And then I'm going to save it as names_file. 51 00:03:53,390 --> 00:03:55,350 Now that I've got this file open 52 00:03:55,350 --> 00:03:57,800 I'm going to go ahead and read it. 53 00:03:57,810 --> 00:04:05,520 So names_file.read. And once I've read it, I'm going to save it to a variable called names and 54 00:04:05,520 --> 00:04:07,410 then I'm going to print out my names. 55 00:04:08,010 --> 00:04:15,960 So now if I go ahead and hit run my main.py, you can see that it prints out all of these names individually 56 00:04:16,200 --> 00:04:19,690 because it's getting hold of everything that's in here and just printing it out. 57 00:04:20,370 --> 00:04:25,650 Now, at this point, I would really like these names to be in the format of a list. 58 00:04:25,980 --> 00:04:32,400 So if you remember, that's where this readlines method is going to be really helpful because it returns 59 00:04:32,400 --> 00:04:36,290 a list containing each line inside the file as a list item. 60 00:04:37,380 --> 00:04:42,330 Now, instead of saying names_file.read, let's replace that with readlines. 61 00:04:43,080 --> 00:04:50,760 Now, when I hit run, you can see it prints out names, and names is now magically turned into a list. 62 00:04:51,180 --> 00:04:59,340 So now that we have our list of names which we've extracted from our invited_names.txt, then 63 00:04:59,340 --> 00:05:06,480 we can go ahead and proceed to the next step where we're going to replace this placeholder in our starting 64 00:05:06,480 --> 00:05:09,160 letter with each of these names. 65 00:05:09,690 --> 00:05:15,840 Let's go ahead and create a constant at the top which I'll call PLACEHOLDER, and I'm going to set 66 00:05:15,840 --> 00:05:23,790 it as the string which is the square brackets and then the word name because this is the string 67 00:05:23,790 --> 00:05:27,200 that we want to replace from our starting letter. 68 00:05:27,900 --> 00:05:31,300 The next step is to open up our starting letter. 69 00:05:31,320 --> 00:05:35,400 So again, I'm going to use open and then I'm going to specify the path. 70 00:05:35,680 --> 00:05:40,820 So from here, I'm going to go into the folder that's at the same level as this file, 71 00:05:41,160 --> 00:05:48,510 so using the ./ and then I'm going to go into input again and then I'm going to go into instead 72 00:05:48,510 --> 00:05:50,340 of names, I'm going to go to letters. 73 00:05:52,320 --> 00:06:00,210 And I'm going to get hold of my starting letter and I'm going to open this as the letter_file. With the 74 00:06:00,210 --> 00:06:00,970 letter_file 75 00:06:00,990 --> 00:06:08,430 I'm simply just going to get a hold of the letter_contents by saying letter_file.read. 76 00:06:08,580 --> 00:06:14,640 And this is going to be a normal read because I want all of the content inside that letter and it's 77 00:06:14,640 --> 00:06:18,390 now going to be saved as a string inside my letter_contents. 78 00:06:19,290 --> 00:06:27,120 The next step is to go through the letter contents and replace that placeholder with the actual name 79 00:06:27,120 --> 00:06:28,590 that we've got in our list. 80 00:06:29,130 --> 00:06:35,940 To do that we'll need the second method that I showed you which is the replace method. So we can get 81 00:06:35,940 --> 00:06:38,640 hold of the text call, replace, 82 00:06:38,880 --> 00:06:44,310 and then the output of this method will be a new string which has modified 83 00:06:44,310 --> 00:06:52,620 this tex. I in our case we'll need a loop. So we can say for name in our list of names, let's go through 84 00:06:52,620 --> 00:07:00,390 each of the names in that list and then let's get the letter_contents and replace the placeholder, 85 00:07:00,390 --> 00:07:05,400 so the old string, with a new string which is going to be the name. 86 00:07:06,120 --> 00:07:11,130 And once we've replaced it, then we're going to save it into a new_letter. 87 00:07:12,610 --> 00:07:18,220 Now that we have our new letter, let's go ahead and print it out and see what it looks like. 88 00:07:21,520 --> 00:07:27,460 So you can see all the contents of each of the letters being printed, but other than the very last 89 00:07:27,460 --> 00:07:33,550 letter that looks pretty normal, every other letter has a new line after the name. 90 00:07:34,120 --> 00:07:40,630 So remember when we printed out each of these names, you can see that after each of the names that 91 00:07:40,630 --> 00:07:46,930 they've extracted from this list of invited names, there's a new line that's being added, 92 00:07:47,140 --> 00:07:49,440 and you can see that with this \n. 93 00:07:49,450 --> 00:07:53,950 The only one that doesn't have a new line is the very last one. 94 00:07:54,670 --> 00:08:00,200 What we need to do is to strip the new line. Does that remind you of something? 95 00:08:00,220 --> 00:08:06,550 Well, we have a method that we saw called strip which can take away any of the spaces at the beginning 96 00:08:06,550 --> 00:08:07,870 and at the end of the string. 97 00:08:08,350 --> 00:08:14,980 And then we can end up with an output which is the string without any of those leading and trailing 98 00:08:14,980 --> 00:08:15,580 spaces. 99 00:08:16,300 --> 00:08:21,370 We're going to loop through each of the names and then we're going to take the name and we're going 100 00:08:21,370 --> 00:08:23,830 to call strip on each of those names. 101 00:08:24,250 --> 00:08:28,420 And then we can save it to a variable called stripped_name. 102 00:08:29,800 --> 00:08:33,580 And now we can use that stripped_name instead of the name. 103 00:08:34,780 --> 00:08:39,370 Now if I go ahead and print out our new_letter, 104 00:08:41,820 --> 00:08:48,390 you can see that each of the letters look exactly like how we want them to be. All we need to do now 105 00:08:48,420 --> 00:08:53,650 is to write them into a new file. In previous lessons 106 00:08:53,670 --> 00:09:01,290 I mentioned that when you open a file that doesn't exist, Python will actually create that file for 107 00:09:01,290 --> 00:09:01,580 you. 108 00:09:02,190 --> 00:09:09,180 Again, using our with open, I'm going to navigate to this ReadyToSend folder. Going from where we 109 00:09:09,180 --> 00:09:10,390 are in main.py, 110 00:09:10,440 --> 00:09:15,950 we're going to go to the output folder and then we're going to go to the ReadyToSend folder. 111 00:09:16,380 --> 00:09:21,430 And then inside the ReadyToSend folder is where we're going to create our new file. 112 00:09:21,960 --> 00:09:27,150 So let's think about what we want our file name to look like. In the intro I showed you 113 00:09:27,150 --> 00:09:33,400 this is the format for each of the files; letter_for_Aang.txt. 114 00:09:33,540 --> 00:09:36,270 And then this part is replaced by each of the names. 115 00:09:36,930 --> 00:09:45,620 So let's write that letter_for_ the name and then .txt. 116 00:09:45,990 --> 00:09:50,600 We can use an fstring to replace this part with the stripped_name. 117 00:09:51,030 --> 00:09:57,240 So now we should be creating a new letter for each of the names in our list of names. 118 00:09:57,930 --> 00:10:03,090 So now let's refer to this file as the completed_letter. 119 00:10:05,100 --> 00:10:10,500 What we want to do with this completed_letter, which at the moment is blank, is we want to write to 120 00:10:10,500 --> 00:10:10,640 it. 121 00:10:11,070 --> 00:10:18,150 So to do that, we have to change the open mode from default which is 'r' for read to 'w' for 122 00:10:18,150 --> 00:10:18,610 write. 123 00:10:19,110 --> 00:10:24,150 And this will allow us to get our completed letter and write to it. 124 00:10:24,690 --> 00:10:25,980 What do we want to write in there? 125 00:10:26,010 --> 00:10:30,120 Well, we want to write the new letter that we've created, of course. 126 00:10:31,780 --> 00:10:40,300 That's pretty much the end of our code, and all we have to do is to go ahead and hit run. And once I 127 00:10:40,300 --> 00:10:45,460 hit run, you can see there's a whole bunch of letters that have been generated over here, 128 00:10:45,740 --> 00:10:51,610 and if I click on each of them, you can see that the name placeholder has now been replaced 129 00:10:51,880 --> 00:10:56,050 and I'm now ready to go to the printers and print all of these out. 130 00:10:57,160 --> 00:11:01,570 So did you manage to figure out how to complete this project? 131 00:11:02,080 --> 00:11:08,050 If not, be sure to review the relevant parts of the lessons today so that you're really confident with 132 00:11:08,050 --> 00:11:11,080 what's going on and you understand all of this code. 133 00:11:11,920 --> 00:11:16,990 If you want to take a look at the completed solution, then head over to the course resources and you'll 134 00:11:16,990 --> 00:11:22,810 find a link to the final project code which actually works even within repl.it. 135 00:11:22,810 --> 00:11:26,940 So you can delete all of these files and you can see it generate them from scratch.