WEBVTT 0 00:00.330 --> 00:03.630 Now that we've understood a little bit more about the terminal commands, 1 00:03.960 --> 00:08.960 let's come back to our Flask code and understand what the code is doing in a 2 00:09.300 --> 00:14.220 little bit more detail. For example, what is this name? 3 00:14.460 --> 00:18.870 Because we're creating this app from this Flask class 4 00:19.230 --> 00:23.310 and in order to initialize a new Flask application, 5 00:23.700 --> 00:27.600 there is only one required input, 6 00:28.020 --> 00:30.210 and that is the import_name. 7 00:31.380 --> 00:33.390 Let's go ahead and print it out. 8 00:33.720 --> 00:38.720 So if we print this __name__ and comment out the rest of our 9 00:39.600 --> 00:42.480 code and hit run, 10 00:43.800 --> 00:48.000 then you can see that it prints out __main_ 11 00:48.030 --> 00:48.863 _. 12 00:49.320 --> 00:54.320 This name is one of the special attributes that's built into Python. 13 00:56.550 --> 00:57.990 At any given point, 14 00:58.170 --> 01:03.170 you could tap into the name to find out what is the current class, function, 15 01:06.030 --> 01:08.460 method, or descriptor's name. 16 01:09.210 --> 01:12.360 And when we get main, what it's telling us is 17 01:12.500 --> 01:17.000 basically we're executing the code in a particular module. 18 01:17.510 --> 01:22.510 So that means it's run as a script or from an interactive prompt, 19 01:23.930 --> 01:27.330 but it's not run from an imported module. 20 01:28.190 --> 01:31.790 It gives us this code here, if the name is equal to main, 21 01:32.090 --> 01:37.090 then execute something only if it's run as a script. 22 01:38.240 --> 01:40.730 This also takes us to 23 01:40.730 --> 01:45.440 one of the common ways that you'll see people run Flask apps. 24 01:45.830 --> 01:50.830 You'll see if __name__ is double equal to _ 25 01:52.460 --> 01:55.250 _main__ as a string, 26 01:55.250 --> 01:59.570 so exactly what was printed just now when we printed out this name, 27 02:00.050 --> 02:01.400 well, if this is the case, 28 02:01.400 --> 02:05.810 then that means we're running the code from within this current file. 29 02:05.990 --> 02:09.200 We're running hello.py. So in that case, 30 02:09.230 --> 02:13.100 we're going to tap into our app and we're going to call the run method. 31 02:13.700 --> 02:15.260 Now this app.run 32 02:15.260 --> 02:20.060 basically does exactly the same thing as when we went into the terminal and 33 02:20.060 --> 02:25.040 we said flask run. But notice when we say flask run, 34 02:25.100 --> 02:28.580 firstly, we have to provide the FLASK_APP environment variable 35 02:29.060 --> 02:33.260 and secondly, we have to stop the code using control + c 36 02:33.680 --> 02:36.680 instead of using our normal run and stop. 37 02:37.010 --> 02:41.480 But if we use app.run, we can now use our standard controls. 38 02:41.540 --> 02:45.050 So I can simply hit run to run this hello.py, 39 02:46.070 --> 02:51.070 and it will start serving up our Flask app at this address just as it did 40 02:51.980 --> 02:56.750 before, when we did flask run. And instead of using control + c to quit, 41 02:56.870 --> 03:01.870 we can simply use the stop to stop our Flask application, 42 03:02.500 --> 03:04.240 making it a lot easier. 43 03:05.230 --> 03:10.180 Basically by providing the name to Flask, Flask 44 03:10.180 --> 03:15.180 will check that this is the current file where the app code is located. 45 03:16.870 --> 03:21.760 And we're not in fact using an imported module. For example, 46 03:21.760 --> 03:26.760 if I was to import the random module and I was to print the random.name, 47 03:32.080 --> 03:36.880 then you can see the first thing that gets printed is the name of that module. 48 03:37.240 --> 03:39.880 But the name that's printed from hello.py 49 03:39.900 --> 03:44.470 which is the file that's being run is simply __main__. 50 03:44.740 --> 03:49.030 So this basically denotes the file that is currently being run 51 03:49.480 --> 03:52.600 and you say, Run 'hello' Well then inside hello 52 03:52.660 --> 03:54.760 name is going to be equal to main. 53 03:58.170 --> 03:58.260 Right.