1 00:00:01,440 --> 00:00:08,950 Great what we have so far is a script that checks if the current time is between these two times and then it 2 00:00:08,950 --> 00:00:13,170 appends these four lines in the hosts file. 3 00:00:13,860 --> 00:00:20,820 So we're talking about a appending because these R plus mode there means that you can read an append 4 00:00:20,910 --> 00:00:22,020 text in your file. 5 00:00:22,080 --> 00:00:28,440 And you know that through writing defers from a appending in that when you write a text in a file you are writing 6 00:00:28,440 --> 00:00:31,760 the text in that empty version of the file. 7 00:00:31,800 --> 00:00:39,420 So with write you'd have only these four lines in your hosts file and not the other ones. Good, that 8 00:00:39,420 --> 00:00:40,280 makes sense. 9 00:00:40,440 --> 00:00:44,740 And that's the first part of our conditional. 10 00:00:44,940 --> 00:00:50,280 And if that happens to be false then we want to execute something here. 11 00:00:50,400 --> 00:00:55,070 That would be to delete these four lines. 12 00:00:55,950 --> 00:01:02,880 Now as you know from all the previous lectures of file handling in this course there's no direct method 13 00:01:02,970 --> 00:01:12,300 to just pass some lines as arguments or as input and then have a delete function that removes those 14 00:01:12,300 --> 00:01:16,950 lines from the file and that makes the situation a bit tricky. 15 00:01:17,040 --> 00:01:27,110 So our input here is this list with these names with these items which means what we can do is well 16 00:01:27,120 --> 00:01:34,240 first logically you want to read this file and check if these names are in here again. 17 00:01:34,530 --> 00:01:37,370 Actually as we did in here more or less. 18 00:01:37,630 --> 00:01:41,060 So let me start with that. 19 00:01:41,940 --> 00:01:44,990 Open hosts. 20 00:01:45,160 --> 00:01:47,150 Temp. That's a file path. 21 00:01:47,370 --> 00:01:52,170 And again here we are reading and appending at the same time. 22 00:01:52,230 --> 00:01:57,240 So we want to use our R plus there. As file. 23 00:01:58,470 --> 00:02:02,300 Let's store this text in 24 00:02:02,310 --> 00:02:06,510 a variable. Good. 25 00:02:06,660 --> 00:02:13,490 And yeah, this will load the text in our content variable as a single string so. 26 00:02:13,810 --> 00:02:16,530 That's probably not the best solution. 27 00:02:16,890 --> 00:02:23,610 So the best solution would be to use the read lies instead which will produce a list of all 28 00:02:23,610 --> 00:02:25,510 the lines in our hosts file. 29 00:02:25,650 --> 00:02:33,420 So for instance this has twenty five lines and will have a list with 25 items where each item represents 30 00:02:33,830 --> 00:02:37,650 a string with each of these lines. 31 00:02:37,650 --> 00:02:44,090 So for instance this would be a first string of the list stored in the content of the variable. 32 00:02:44,160 --> 00:02:51,150 So content is now a list. Now that we have a list, we can start checking these items against 33 00:02:51,150 --> 00:02:55,330 the list that we have grabbed from hosts file. 34 00:02:55,470 --> 00:03:03,730 So if these items are there we want to delete them but as I said there is not a direct way to delete these items. 35 00:03:03,810 --> 00:03:08,480 We have methods to write content. 36 00:03:08,510 --> 00:03:14,340 So we have methods to append content in that file but not to delete. 37 00:03:14,610 --> 00:03:18,670 However we can make use of the append method. 38 00:03:19,230 --> 00:03:28,680 We could start iterating through these items in the content list and check if Facebook is in that 39 00:03:28,680 --> 00:03:29,780 particular item. 40 00:03:29,790 --> 00:03:35,590 So the items string if Facebook is there then we ignore that line. 41 00:03:35,910 --> 00:03:40,910 And if Facebook is not there we write that line the hosts file. 42 00:03:41,190 --> 00:03:42,930 So something like this. 43 00:03:42,990 --> 00:03:47,200 Let's say we iterate through this and say Facebook is not there. 44 00:03:47,220 --> 00:03:53,970 So create a hosts file like a new hosts file with this line there and then go to the next line. 45 00:03:53,970 --> 00:04:00,900 If Facebook is not there then add, append this line to that hosts file so we will have two lines and then three lines 46 00:04:01,660 --> 00:04:05,160 and then we will remove the lines which contain Facebook. 47 00:04:05,160 --> 00:04:11,650 I know this sounds very confusing at the moment but once I write the script and I explain line 48 00:04:11,660 --> 00:04:12,310 by line, 49 00:04:12,480 --> 00:04:15,660 I'm sure you'll have that moment when you say Aha. 50 00:04:16,050 --> 00:04:17,490 So you'll get that 51 00:04:17,690 --> 00:04:19,690 Once I write the lines here. 52 00:04:20,190 --> 00:04:27,210 So we're here, we read the lines but as you know when you apply a read method like read 53 00:04:27,210 --> 00:04:32,990 lines or read the pointer will be placed at the end of the last line. 54 00:04:33,000 --> 00:04:38,420 So here. So we read the lines there, we have a list. 55 00:04:38,520 --> 00:04:40,170 Now we can say for 56 00:04:42,820 --> 00:04:53,310 line in content. So we start looping through the content list and here I'd use use any method. 57 00:04:53,520 --> 00:05:02,480 So we want to check these items against the lines of content that would be something like if not any 58 00:05:04,880 --> 00:05:11,720 website in line for website in website list 59 00:05:16,100 --> 00:05:22,160 file.write so append the line. 60 00:05:22,160 --> 00:05:27,580 So what I did here is let me simplify that by talking about the first iteration only. 61 00:05:27,830 --> 00:05:32,450 So we have this line here the first line copyright etcetera. 62 00:05:32,930 --> 00:05:44,100 And we are saying that if not any websites so any item which is still a variable in that line. 63 00:05:44,120 --> 00:05:52,400 So in this line and so what is this a website variable that well where the website is the first item of the 64 00:05:52,400 --> 00:06:02,660 website list which should be based on here but this will create a loop so it will check the first item 65 00:06:02,660 --> 00:06:05,990 there and it will compare it. 66 00:06:05,990 --> 00:06:09,030 So against the first line. 67 00:06:09,410 --> 00:06:17,920 So we are in the first loop and we say if not www.Facebook.com 68 00:06:17,930 --> 00:06:19,380 in that first line there. 69 00:06:19,650 --> 00:06:22,900 Then write that line in the file. 70 00:06:22,940 --> 00:06:25,290 Otherwise we wouldn't do anything. 71 00:06:25,430 --> 00:06:26,250 So that would 72 00:06:26,270 --> 00:06:33,770 check the first item of the list and then go to the second item and check it against the first item 73 00:06:33,830 --> 00:06:35,930 of the hosts file. 74 00:06:36,160 --> 00:06:43,370 The first line of hosts file and then it would go to the third line and fourth line until this list is consumed. 75 00:06:43,390 --> 00:06:43,670 76 00:06:44,000 --> 00:06:51,830 So that's for the first line of the hosts file. Than it goes to the second line and performs exactly 77 00:06:51,830 --> 00:06:53,770 the same thing. 78 00:06:53,960 --> 00:06:58,300 So it checks the four items of the website list again. 79 00:06:58,490 --> 00:07:04,770 Against the second line of the hosts file. I hope that makes sense. 80 00:07:04,870 --> 00:07:07,410 And I'll check what this does. 81 00:07:07,760 --> 00:07:12,150 But now it's 20 past four. 82 00:07:12,260 --> 00:07:14,340 So we are in the working hours. 83 00:07:14,500 --> 00:07:22,900 And let me modify this. Let's say 16 to 17 are working hours. 84 00:07:23,090 --> 00:07:28,990 So outside of this we want to move these four lines which will be the case. 85 00:07:29,080 --> 00:07:32,240 Even when I write the script now. 86 00:07:32,400 --> 00:07:35,610 Python website blocker. Run fun hours 87 00:07:35,630 --> 00:07:40,770 is executed and two times. 88 00:07:40,990 --> 00:07:44,780 I'll interrupt this and check what we got. 89 00:07:44,780 --> 00:07:57,790 So we have this block here. We have this block here and then the block is repeated. 90 00:07:58,220 --> 00:08:02,690 So it's not exactly what we want. 91 00:08:02,810 --> 00:08:03,700 And then this ends. 00:08:03,740 --> 00:08:14,510 And then it repeats again and it ends in here then it repeats another time so the loop, the while loop run 92 00:08:14,510 --> 00:08:18,720 three times. And the first block, 93 00:08:18,830 --> 00:08:26,870 so this one here was the block that we had already in the hosts file and then what happened is 94 00:08:26,870 --> 00:08:33,860 that we opened this hosts file in read and append mode and then iterated through the lines of the hosts 95 00:08:33,860 --> 00:08:42,740 file and then we said append only those lines where there's no Facebook or this mail.live 96 00:08:42,780 --> 00:08:50,420 in those lines. And Python did just that so it appended those lines under the existing 97 00:08:50,420 --> 00:08:53,580 content and it did it two times. 98 00:08:53,900 --> 00:08:54,330 Yes. 99 00:08:54,500 --> 00:09:02,360 Sorry, I set the loop around three times earlier actually the loop the loop ran two times but we had one 100 00:09:02,360 --> 00:09:03,690 existing block here. 101 00:09:03,980 --> 00:09:07,510 So the other two times Python appended 102 00:09:08,220 --> 00:09:16,560 this block again. Great. Even though we are not there yet, I'm satisfied with the progress because I think you 103 00:09:16,610 --> 00:09:19,840 are now able to understand how things are working. 104 00:09:20,240 --> 00:09:27,560 And now we need to put our logic into a very active state in order to make this work. 105 00:09:27,590 --> 00:09:30,820 So there are no new things that you need to apply here. 106 00:09:30,890 --> 00:09:32,700 It's just tricks. 107 00:09:32,870 --> 00:09:41,600 So you know about this truncate method which is what it does is it truncates it deletes the content 108 00:09:41,600 --> 00:09:47,010 of the file from the current point and downwards. 109 00:09:47,030 --> 00:09:50,950 So for instance if we apply that in here 110 00:09:53,910 --> 00:09:56,760 what we would get is� 111 00:09:57,160 --> 00:10:07,130 So think about the first iteration. So the first iteration will add the first block after the existing 112 00:10:07,130 --> 00:10:10,490 block which is this one here. 113 00:10:11,740 --> 00:10:18,300 So this is the first block with all of the Facebook things. The truncate method what it would do, 114 00:10:18,330 --> 00:10:26,310 it will delete everything that is under this, which is not exactly what we want 115 00:10:26,320 --> 00:10:31,760 because we would still have these things above. 116 00:10:31,780 --> 00:10:42,330 So we need to figure out a way to put this block of code above this, above the existing one and to solve 117 00:10:42,340 --> 00:10:47,360 that is by using file.seek. 118 00:10:47,830 --> 00:10:53,680 So you know that when you read it when you apply or methods to your file for instance here you apply 119 00:10:53,680 --> 00:10:59,220 the first read method and the pointer will go here. 120 00:10:59,250 --> 00:11:03,320 So just after the last character of the file content. 121 00:11:03,340 --> 00:11:10,630 So when you apply a write method and you append lines, the lines will append after the pointer. 122 00:11:10,670 --> 00:11:11,860 123 00:11:11,870 --> 00:11:18,460 Now if you want to append these lines as I said if you want to append them before this existing block 124 00:11:18,940 --> 00:11:24,650 you'd want to apply the seek method so that you replace the pointer. 125 00:11:24,670 --> 00:11:30,480 You replace the pointer just before the first character of the file content. 126 00:11:30,880 --> 00:11:37,480 What that will do is it will get all these lines. 127 00:11:37,600 --> 00:11:46,750 So cut it from there just to illustrate and it will replace them in here and there what the file truncate method 128 00:11:46,750 --> 00:11:52,170 will do is it will remove everything that is after that. 129 00:11:52,960 --> 00:11:54,070 And this as well. 130 00:11:54,150 --> 00:12:00,110 So we will end up with this text which is what we want. 131 00:12:00,460 --> 00:12:06,210 Good. I hope I explained that well and let me try that now. 132 00:12:07,210 --> 00:12:13,250 So it will delete these and these. 133 00:12:14,320 --> 00:12:17,600 This is the initial state of the hosts file. 134 00:12:17,680 --> 00:12:21,710 So we have these Facebook and Hotmail domains there. 135 00:12:21,970 --> 00:12:23,340 So I'll save this. 136 00:12:23,800 --> 00:12:34,180 And the script as well and I'll go ahead and execute. 137 00:12:34,600 --> 00:12:37,250 So it seems to be working well. 138 00:12:38,240 --> 00:12:39,860 Yes. 139 00:12:41,490 --> 00:12:44,980 And if I change the hour so let me� 140 00:12:48,190 --> 00:12:58,610 Alright, I'll do a soft ware there. Ok. So that you see both the hosts file and the script. 141 00:12:58,690 --> 00:13:01,160 So now it's three to four. 142 00:13:01,150 --> 00:13:05,120 And let me put this to 15. 143 00:13:05,230 --> 00:13:16,920 So we are in the working hours. Execute this. And the lines are there. Interrupt that. Put this 16. Try again. 144 00:13:17,080 --> 00:13:17,510 145 00:13:17,620 --> 00:13:20,530 And the lines are gone. 146 00:13:20,620 --> 00:13:27,330 So this is working. Again just to wrap up what we did here is 147 00:13:27,340 --> 00:13:34,660 so if we're talking about the else section and we opened the hosts file in read and append method. 148 00:13:34,670 --> 00:13:35,070 149 00:13:35,620 --> 00:13:43,720 And then we stored the lines in content list and that puts a pointer in here which means that everything 150 00:13:43,720 --> 00:13:47,140 you do after that will be applied under these lines. 151 00:13:47,530 --> 00:13:55,550 But by applying the seek method there we tell Python to put the pointer in here just here. 152 00:13:55,630 --> 00:14:04,950 And so then we iterate through this content list in this line and check that if any of these website 153 00:14:04,990 --> 00:14:09,840 list contents is in the current line of the content list� 154 00:14:09,900 --> 00:14:17,680 Actually if it is not in the current line of content list, then we write down that line in the hosts file. 155 00:14:17,690 --> 00:14:26,170 And we truncate everything that goes under that line which means we wrote all these twenty one 156 00:14:26,470 --> 00:14:33,840 lines and everything that we had down here, so which was th previous existing hosts text that content 157 00:14:34,060 --> 00:14:35,400 was truncated. 158 00:14:35,400 --> 00:14:37,820 So it was deleted from the file. 159 00:14:38,020 --> 00:14:41,080 And yes we're basically done. 160 00:14:41,390 --> 00:14:47,710 I mean we still have some things to make this work to be able to run this script as a Python 161 00:14:47,710 --> 00:14:48,240 process 162 00:14:48,250 --> 00:14:55,970 on the background because at the moment the way we run this is by opening a command line like calling 163 00:14:55,980 --> 00:15:00,040 Python and then pointing to website blocker.py. 164 00:15:01,030 --> 00:15:03,780 And also we need to implement one thing. 165 00:15:03,790 --> 00:15:12,090 So at the moment we are accessing this fake hosts file but what we want to do instead is access the 166 00:15:12,100 --> 00:15:16,570 actual hosts file which is here. 167 00:15:16,640 --> 00:15:25,030 So hosts and to do that you'd first want to change host temp with hosts path. 168 00:15:25,330 --> 00:15:27,740 So you hosts temp with hosts path. 169 00:15:27,850 --> 00:15:32,530 So where do we have hosts temp. Hosts. 170 00:15:32,710 --> 00:15:34,560 Yeah it's here. 171 00:15:35,860 --> 00:15:40,790 Hosts path there and here as well. 172 00:15:43,170 --> 00:15:44,350 Now that's about it. 173 00:15:44,380 --> 00:15:47,200 But if you try this 174 00:15:50,830 --> 00:15:55,660 you get a permission error because you're runing that as a normal user. 175 00:15:55,720 --> 00:16:03,260 What you want to do instead is run that as an administrator or on Linux or Mac that is straightforward. 176 00:16:03,310 --> 00:16:03,370 177 00:16:03,370 --> 00:16:05,430 So you'd want to say sudo. 178 00:16:05,500 --> 00:16:08,670 And then Python and then point to website blocker.py. 179 00:16:08,910 --> 00:16:12,400 However sudo doesn't work with Windows. 180 00:16:12,520 --> 00:16:20,650 So the work around here is to open the command line from the terminal and right click and go run as 181 00:16:20,640 --> 00:16:21,910 administrator. 182 00:16:22,380 --> 00:16:22,990 Yes. 183 00:16:23,020 --> 00:16:27,610 And then you'd have to cd for change directory and then 184 00:16:30,580 --> 00:16:35,010 Slash d which means I'm going to the D drive. 185 00:16:35,020 --> 00:16:39,600 So when you switch drives from C to D you want to use this backslash D. 186 00:16:40,290 --> 00:16:42,290 Dropbox. 187 00:16:48,650 --> 00:16:49,550 Block websites. 188 00:16:49,610 --> 00:16:50,300 And demo. 189 00:16:54,520 --> 00:16:55,840 And if I run the script now. 190 00:16:55,840 --> 00:17:01,950 Python and website blocker, that runs normaly. 191 00:17:02,860 --> 00:17:04,610 So we are during the fun hours. 192 00:17:04,620 --> 00:17:09,390 It's 15 16 past 6. 193 00:17:09,390 --> 00:17:12,570 So we are in the fun hours. 194 00:17:15,260 --> 00:17:22,330 and if you check the script, the hosts file you'll see that you don't have any web sites 195 00:17:22,340 --> 00:17:25,370 there being blocked. 196 00:17:25,520 --> 00:17:27,870 So let me try this. 197 00:17:27,880 --> 00:17:34,840 Let me change this to 19 so that will fall inside the working hours and run rather script again so we 198 00:17:34,840 --> 00:17:36,350 get the working hours there. 199 00:17:36,590 --> 00:17:43,450 And if I go and check the Notepad now it is saying this file has been modified by another program 200 00:17:44,200 --> 00:17:45,300 which is Python. 201 00:17:45,340 --> 00:17:46,610 And do you want to reload it. 202 00:17:46,680 --> 00:17:49,230 Yes. 203 00:17:49,300 --> 00:17:51,680 We have these four lines there. 204 00:17:52,790 --> 00:17:58,270 If I try Facebook now I won't be able to access it. 205 00:17:59,130 --> 00:18:06,220 But be aware though that sometimes if you have your browser open and you will you just block Facebook 206 00:18:06,220 --> 00:18:10,770 or another website in your hosts file, the browser may not reflect it immediately. 207 00:18:10,920 --> 00:18:16,890 So it may take some time ntil the browser can get the information from the hosts file. 208 00:18:17,380 --> 00:18:22,920 If you want to speed up the process you may want to restart your browser so close it and open up again 209 00:18:23,390 --> 00:18:26,260 and then check Facebook. 210 00:18:26,520 --> 00:18:30,370 And yet it should be the same for Hotmail as well. 211 00:18:30,370 --> 00:18:38,170 So it passes Hotmail but then Hotmail layer servers direct you to this Web site which I'm blocking and 212 00:18:38,160 --> 00:18:39,840 you cannot access that either. 213 00:18:40,200 --> 00:18:42,930 So this is working well we're doing great. 214 00:18:43,060 --> 00:18:48,300 And yeah, what's left now is to implement this program to run it in the background. 215 00:18:48,490 --> 00:18:52,910 So that's just a few minutes of video left for this section 216 00:18:53,030 --> 00:18:55,190 And we're done, so talk to you in the next lecture.