1 00:00:00,600 --> 00:00:01,589 Instructor: In this exercise, 2 00:00:01,589 --> 00:00:05,100 you're going to create your very own decorator function 3 00:00:05,100 --> 00:00:07,890 and your decorator function is going to do something 4 00:00:07,890 --> 00:00:09,390 that a lot of you are curious about, 5 00:00:09,390 --> 00:00:11,370 which is how long does it take 6 00:00:11,370 --> 00:00:13,260 for a particular function to run? 7 00:00:13,260 --> 00:00:15,720 Is my function efficient? 8 00:00:15,720 --> 00:00:18,270 Is it as fast as possible? 9 00:00:18,270 --> 00:00:20,640 Well, you'll actually get a numerical answer 10 00:00:20,640 --> 00:00:24,060 to that question by completing this current challenge. 11 00:00:24,060 --> 00:00:26,130 So how is time calculated? 12 00:00:26,130 --> 00:00:29,190 Well, in Python, there is a module called time 13 00:00:29,190 --> 00:00:31,650 and you can run time.time 14 00:00:31,650 --> 00:00:33,900 in order to get the current time 15 00:00:33,900 --> 00:00:38,900 since 1st of January, 1970 at midnight. 16 00:00:39,300 --> 00:00:43,170 Try running the starting code and seeing what gets printed 17 00:00:43,170 --> 00:00:45,930 as the current time each time you run it. 18 00:00:45,930 --> 00:00:46,920 Hopefully you'll notice 19 00:00:46,920 --> 00:00:49,320 that that number increments each time 20 00:00:49,320 --> 00:00:53,400 and it represents the number of seconds since 1970. 21 00:00:53,400 --> 00:00:57,150 So as time goes on, that number will go up. 22 00:00:57,150 --> 00:00:58,920 Think about how you can use that 23 00:00:58,920 --> 00:01:01,470 to create a decorator function 24 00:01:01,470 --> 00:01:03,900 and write your decorator function 25 00:01:03,900 --> 00:01:07,830 inside a speed_calc_decorator, and then apply that 26 00:01:07,830 --> 00:01:11,040 to both the fast_function and the slow_function 27 00:01:11,040 --> 00:01:14,580 in order to see how long it takes each of them to execute. 28 00:01:14,580 --> 00:01:17,610 That's the goal of this challenge, and remember 29 00:01:17,610 --> 00:01:19,920 to take a look inside the description box to see 30 00:01:19,920 --> 00:01:24,360 how it should behave, and also look at the hint 31 00:01:24,360 --> 00:01:26,010 if you get stuck. 32 00:01:26,010 --> 00:01:26,843 Have a go now. 33 00:01:35,084 --> 00:01:36,240 The first thing we need to do 34 00:01:36,240 --> 00:01:39,483 is to define our speed_calc_decorator, 35 00:01:41,220 --> 00:01:43,530 and we're going to add an input 36 00:01:43,530 --> 00:01:46,560 to this function, which is also a function. 37 00:01:46,560 --> 00:01:49,440 It's basically the function that we're gonna be decorating 38 00:01:49,440 --> 00:01:52,950 and now we can access that function inside the body 39 00:01:52,950 --> 00:01:55,740 of the speed_calc_decorator. 40 00:01:55,740 --> 00:01:58,680 Next, we're going to define our wrapper_function. 41 00:01:58,680 --> 00:02:01,740 And this wrapper_function is going to be the one 42 00:02:01,740 --> 00:02:03,783 that's calculating the time. 43 00:02:05,220 --> 00:02:06,300 Inside the wrapper_function, 44 00:02:06,300 --> 00:02:09,090 the first thing we define is the start_time 45 00:02:09,090 --> 00:02:10,800 using time.time. 46 00:02:10,800 --> 00:02:12,720 And this will give us the number of seconds 47 00:02:12,720 --> 00:02:15,510 since January 1st, 1970. 48 00:02:15,510 --> 00:02:18,540 And then we run the function that's being passed in, 49 00:02:18,540 --> 00:02:21,210 which is going to be the function that we decorate. 50 00:02:21,210 --> 00:02:25,230 And this could be the slow_function or the fast_function 51 00:02:25,230 --> 00:02:27,870 or any other function for that matter. 52 00:02:27,870 --> 00:02:30,480 And then after that function is completed, 53 00:02:30,480 --> 00:02:32,460 then we calculate the end_time. 54 00:02:32,460 --> 00:02:36,363 Well, what is the time now since January 1st, 1970? 55 00:02:37,800 --> 00:02:40,230 Finally, we can write our print function 56 00:02:40,230 --> 00:02:44,280 and using an f string, we substitute the function.__name, 57 00:02:44,280 --> 00:02:47,430 which is the name of the function that got passed in, 58 00:02:47,430 --> 00:02:49,620 which is the function that we're decorating. 59 00:02:49,620 --> 00:02:53,520 And then we are printing the run speed of that function. 60 00:02:53,520 --> 00:02:55,320 And that is, of course, calculated 61 00:02:55,320 --> 00:02:58,199 by the end_time subtracting from the start_time. 62 00:02:58,199 --> 00:03:01,560 And we end up with the number of seconds that has elapsed 63 00:03:01,560 --> 00:03:05,493 for the function that was passed in to finish running. 64 00:03:06,360 --> 00:03:09,690 And then finally, we return our wrapper_function 65 00:03:09,690 --> 00:03:13,590 and that completes the definition of our decorator. 66 00:03:13,590 --> 00:03:17,040 Now all that's left to do is to decorate our functions 67 00:03:17,040 --> 00:03:19,050 that we want to apply this to. 68 00:03:19,050 --> 00:03:23,010 So on line 13 and 18, I'm adding the speed_calc_decorator 69 00:03:23,010 --> 00:03:25,620 to the fast_function and the slow_function. 70 00:03:25,620 --> 00:03:27,720 And finally, on line 23 and 24, 71 00:03:27,720 --> 00:03:29,670 I'm actually running those functions, 72 00:03:29,670 --> 00:03:32,973 which will carry along with it the decorator functions. 73 00:03:34,020 --> 00:03:35,670 So now if you ran the code, 74 00:03:35,670 --> 00:03:38,130 you would see how long it took for the fast_function to run, 75 00:03:38,130 --> 00:03:40,380 how long it took for the slow_function to run. 76 00:03:40,380 --> 00:03:41,700 And you can see each time, 77 00:03:41,700 --> 00:03:44,220 we're applying the speed_calc_decorator to each one 78 00:03:44,220 --> 00:03:46,503 of them and printing out the running time.