1 00:00:01,710 --> 00:00:06,390 If you followed the previous sections of the course then you have come by a long way. 2 00:00:06,540 --> 00:00:09,320 So you now know the fundamentals of Python. 3 00:00:09,390 --> 00:00:11,830 You know how to solve fundamental problems. 4 00:00:11,850 --> 00:00:15,780 For example let's say you wanted the number of characters of this string. 5 00:00:15,990 --> 00:00:20,030 So you have methods and you have functions that you can use. 6 00:00:20,030 --> 00:00:26,970 So for methods you can search with dir str you'd see a bunch of methods here that could be applied 7 00:00:27,000 --> 00:00:29,160 to strings and then you could see 8 00:00:31,740 --> 00:00:34,290 functions, built in functions. 9 00:00:34,290 --> 00:00:37,020 For example the len method would be handy here. 10 00:00:37,050 --> 00:00:45,900 It would return the number of characters for the pypypy string which is six. 11 00:00:46,080 --> 00:00:48,240 Now all these here. 12 00:00:48,240 --> 00:00:52,980 So these functions and the string methods they are all built in. 13 00:00:53,250 --> 00:00:59,820 So these are methods and functions that are written inside the python software that you download and 14 00:00:59,820 --> 00:01:01,100 install from Python 15 00:01:01,100 --> 00:01:02,370 Dot org. 16 00:01:02,640 --> 00:01:05,480 So that software is written in C language. 17 00:01:05,550 --> 00:01:11,010 Therefore these methods and functions are also written in C language. 18 00:01:11,160 --> 00:01:17,020 And as you see these names here are available immediately in your Python interpreter. 19 00:01:17,070 --> 00:01:18,230 That means they are built in. 20 00:01:18,240 --> 00:01:23,280 They are inside that interpreter, and you can just call them without importing them. 21 00:01:23,280 --> 00:01:32,320 Now what if we had some other problems like let's say, you see this script here. 22 00:01:32,970 --> 00:01:35,080 What this script is doing is... 23 00:01:35,100 --> 00:01:35,760 It's a loop. 24 00:01:35,760 --> 00:01:37,200 It's a while loop. 25 00:01:37,440 --> 00:01:40,680 So while true which means it will run forever. 26 00:01:40,680 --> 00:01:48,330 So what it does is it's reading this file vegetable.txt in the files directory which happens 27 00:01:48,330 --> 00:01:51,930 to be in the same directory with basics.py. 28 00:01:52,170 --> 00:02:02,090 So that is the path of the file and this text file contains this string, so I'm reading it under this variable, 29 00:02:02,700 --> 00:02:05,760 and I'm printing all the content in here. 30 00:02:05,750 --> 00:02:14,630 So if I execute this file you're going to get the content printed out every split of a second and which 31 00:02:14,630 --> 00:02:18,380 depends on your processor speed, on your computer processor speed. 32 00:02:18,380 --> 00:02:23,090 Now what if we don't want this to happen every split of a second. 33 00:02:23,090 --> 00:02:25,820 What if you want to read the content every 10 seconds. 34 00:02:26,050 --> 00:02:33,860 Let me interrupt this with control c, you'd soon realize that you don't have any built in function 35 00:02:34,070 --> 00:02:43,260 that does that, that implements some sort of sleep methods in your script, so there's no function that 36 00:02:43,260 --> 00:02:45,020 you can use right away. 37 00:02:45,120 --> 00:02:50,250 In that case you may want to look for built in modules. To do that 38 00:02:50,250 --> 00:03:06,310 please use this syntax import sys which stands for system and sys.builtin_module_names, and here 39 00:03:06,320 --> 00:03:13,640 you'll get a list of modules, built in modules, some modules that are built in again in the Python software. 40 00:03:13,700 --> 00:03:20,990 So let's use one of them, time, the way you use it is by importing the module name and then again you 41 00:03:20,990 --> 00:03:24,730 can use dir to see what you have for that module. 42 00:03:24,830 --> 00:03:29,600 For example here you'll see we have a sleep method. 43 00:03:29,900 --> 00:03:34,480 Use help to see how to use that particular method. 44 00:03:34,760 --> 00:03:40,420 So it says that it gets the sequence as argument so let's try it. 45 00:03:40,430 --> 00:03:41,970 time.sleep. 46 00:03:41,990 --> 00:03:46,180 Let's say 3. 1, 2, 3. 47 00:03:46,280 --> 00:03:49,640 And? So what time that sleep does? It sleeps 48 00:03:49,640 --> 00:03:54,340 the script execution for a particular amount of seconds. 49 00:03:54,350 --> 00:03:58,370 Three in this case, that means we can implement that in the script. 50 00:03:58,850 --> 00:04:07,580 It's a good practice to import modules in the first line of the script, and then use that module in your 51 00:04:07,580 --> 00:04:09,740 script wherever you need it. 52 00:04:09,740 --> 00:04:13,900 In this case what you want to do is let's suppose this vegetables.txt file 53 00:04:13,910 --> 00:04:19,880 is being generated on our server every 10 seconds. 54 00:04:19,910 --> 00:04:26,750 So let's say as software in the server is getting this data from somewhere and it's a writing a new 55 00:04:26,750 --> 00:04:32,600 content every 10 seconds, for example now is tomato, later it's going to be garlic. 56 00:04:32,600 --> 00:04:35,690 10 seconds after that it it'll be onion and so on. 57 00:04:35,840 --> 00:04:38,810 So we are getting new content every 10 seconds. 58 00:04:38,810 --> 00:04:50,210 So we want to print all the contents of the file and then have the execution sleep for 10 seconds. 59 00:04:50,210 --> 00:04:59,800 Now I'm going to save the script, go to command line, execute it, so you get tomato right away. 60 00:04:59,800 --> 00:05:05,800 Now if I change these to onion, let's say the software changed it and save. 61 00:05:05,800 --> 00:05:10,120 Click save an onion was printed out there after 10 seconds. 62 00:05:10,120 --> 00:05:12,640 If I change it to garlic, save. 63 00:05:15,520 --> 00:05:17,260 Wait, wait a few seconds. 64 00:05:17,260 --> 00:05:24,490 Garlic is printed out there so every 10 seconds the script is fetching the data from vegetables.txt 65 00:05:24,490 --> 00:05:28,140 and printing it out on the command line. 66 00:05:30,360 --> 00:05:33,400 So controlled C to interrupt it. 67 00:05:33,390 --> 00:05:38,170 This is how you use a module. 68 00:05:38,240 --> 00:05:43,300 Now not everything is built in in your Python interpreter software. 69 00:05:43,340 --> 00:05:50,060 Some things actually many of them come in a different form that I'm going to explain in the next lecture.