WEBVTT 00:00.120 --> 00:01.040 Welcome back. 00:01.040 --> 00:03.400 Now let's start with functions. 00:03.640 --> 00:08.000 A function is a block of code that runs only when called. 00:08.000 --> 00:13.200 You can pass data known as parameters, into a function. 00:13.240 --> 00:16.720 A function can return data as a result. 00:16.760 --> 00:20.720 Use def the keyword def to define a function. 00:20.760 --> 00:30.040 Here we are creating a function called greet taking name as parameter and inside this function we have 00:30.040 --> 00:35.480 this print statement printing hello and the passed variable. 00:35.600 --> 00:38.080 This is the function declaration. 00:38.080 --> 00:43.960 So here we are creating and defining a function using the def keyword. 00:44.080 --> 00:49.800 To call a function, use the function name followed by parentheses. 00:50.080 --> 00:55.680 Here we have this function greet and a parameter name. 00:55.840 --> 01:03.000 In order to call the function, we need to call the the the name of the function followed by parentheses. 01:03.040 --> 01:11.180 Inside the parenthesis we define the arguments which later becomes parameters and use them. 01:11.340 --> 01:11.900 Okay. 01:12.060 --> 01:14.020 So let me run this function. 01:14.020 --> 01:15.020 And here we go. 01:15.340 --> 01:17.940 We have hello Alice. 01:18.060 --> 01:20.740 Another run of this function. 01:20.980 --> 01:28.340 Another call passing Bob as a parameter will give us hello Bob. 01:28.380 --> 01:33.220 Information can be passed into functions as arguments. 01:33.420 --> 01:39.620 Arguments are specified after the function name inside the parenthesis. 01:39.860 --> 01:46.220 You can add as many arguments as you want, just separate them with a comma. 01:46.220 --> 01:55.580 So here if I want to add another argument which is of type integer if you want your age years old. 01:55.620 --> 02:03.140 If I run the application we get an error because here we need to pass two parameters the name and age. 02:03.540 --> 02:08.650 So pass the age of Alice 18 Run! 02:08.650 --> 02:09.530 And here we go. 02:09.690 --> 02:10.890 Hello, Alice. 02:10.930 --> 02:13.890 Your age is 18 years old. 02:14.130 --> 02:14.770 Okay. 02:14.810 --> 02:21.730 When the function is called, we pass along the first name and the age. 02:21.970 --> 02:27.370 The terms parameter and argument can be used for the same thing. 02:27.530 --> 02:31.210 Information that are passed into a function. 02:31.210 --> 02:39.930 From a function's perspective, a parameter is a variable listed inside the parentheses in the function. 02:39.930 --> 02:40.570 Define. 02:40.610 --> 02:46.010 An argument is the value that is sent to the function when it's called. 02:46.010 --> 02:50.250 So this is called argument and this is called parameter. 02:50.250 --> 02:56.210 By default, a function must be called with the correct number of arguments, meaning that if the function 02:56.210 --> 03:02.610 expects two arguments exactly like the greet function, you have to call the function with two arguments, 03:02.730 --> 03:04.850 not more and not less. 03:04.850 --> 03:11.130 I can't pass here, for example, 99.56. 03:11.170 --> 03:15.990 If I run, we get an error because this is an extra argument. 03:16.030 --> 03:24.390 One last interesting thing about functions in Python we can pass the default parameter value. 03:24.630 --> 03:33.550 For example, here inside this function let me create a another parameter. 03:33.670 --> 03:38.910 It's of name email and I can give it a default value. 03:38.910 --> 03:44.030 For example a at gmail.com okay. 03:44.190 --> 03:47.590 And here print your email is email. 03:47.710 --> 03:56.230 If I run the application the application runs perfectly because here we have three parameters. 03:56.350 --> 04:00.110 And I pass two parameters and two arguments. 04:00.390 --> 04:02.670 Why it works. 04:02.870 --> 04:05.470 Because here we have a default value. 04:05.470 --> 04:10.150 And if we see your email is a at gmail.com. 04:10.350 --> 04:21.850 If I need to override the default value of the email here we can pass for example CC at com. 04:21.890 --> 04:24.810 Run the application again and here we go. 04:25.050 --> 04:28.370 Your email is CC at gmail.com. 04:28.370 --> 04:36.730 So the default parameter value can be specified by the equal sign in the function. 04:36.890 --> 04:42.210 If we call the function without argument, it uses the default value. 04:42.410 --> 04:51.290 If we call the function with the argument, it will use the argument and override the default value. 04:51.410 --> 04:58.050 Functions can return a value using return statement, for example. 04:58.330 --> 04:59.890 Def square. 05:00.210 --> 05:08.210 We are defining a new function named as square, taking into the parameters a variable x. 05:08.250 --> 05:09.810 X return. 05:10.290 --> 05:17.610 The return statement will return a value of this function x times x. 05:17.650 --> 05:20.320 This is the arithmetic operation. 05:20.360 --> 05:29.720 The product of x times x, which is x squared or x to power x or um sorry not x. 05:30.160 --> 05:35.000 It's x squared because here we have to x times x okay. 05:35.160 --> 05:42.960 The result here is a valuable equals to the returning type of the square. 05:42.960 --> 05:48.480 So here I am calling the function square passing five as an argument. 05:48.840 --> 05:52.560 The returning type will be five times five. 05:52.560 --> 05:56.240 So it will return 25 okay. 05:56.640 --> 06:04.360 The result will be stored inside the result variable and would be printed here using the statement. 06:04.400 --> 06:09.080 The square of f or of five is 25. 06:09.240 --> 06:14.600 Okay, so this is how we define functions in Python. 06:14.800 --> 06:17.320 How to pass parameters. 06:17.320 --> 06:22.920 How to return a resulting value of this function.