1 00:00:04,970 --> 00:00:09,740 Our multiply function isn't very useful. It multiplies 10.5 by 4 and 2 00:00:30,300 --> 00:00:31,680 Alright, so we're going to get our function 3 00:00:31,680 --> 00:00:36,180 to multiply two numbers, then return the result. To do that, we need 4 00:00:36,180 --> 00:00:40,540 some way to get the numbers into the function, so that it knows what to multiply, 5 00:00:40,540 --> 00:00:44,800 rather than hard coding the numbers, as we're doing on line 2. So this is what 6 00:00:44,800 --> 00:00:48,560 function parameters are for. So I'm going to add two parameters to our function, 7 00:00:48,560 --> 00:00:55,460 so I'm going to come up here, and within the parentheses I'm going to type x comma space y. 8 00:01:17,160 --> 00:01:19,260 Alright, so now that we've declared two 9 00:01:19,260 --> 00:01:23,160 parameters in our function, we can use them instead of the hard-coded literal 10 00:01:23,160 --> 00:01:29,500 values on line two. Let's go ahead and do that. I'm going to change a 10.5 to x, and 4, 11 00:01:29,500 --> 00:01:34,920 I'm going to change to y. Whatever values we provide for those parameters, 12 00:01:34,920 --> 00:01:39,320 will be used when we call the function. When a function has parameters, 13 00:01:39,320 --> 00:01:44,039 you must provide suitable values when you call the function. Now it's hard to 14 00:01:44,039 --> 00:01:48,329 see this because of the break point, but I've got a warning on line six. If I hover, 15 00:01:48,329 --> 00:01:51,549 now, over the parentheses after the function name, 16 00:01:51,549 --> 00:01:55,160 you can see that IntelliJ is telling me that parameter x is unfilled, 17 00:01:55,160 --> 00:02:01,540 and parameter y is unfilled. We can fix that by providing the arguments. 18 00:02:26,460 --> 00:02:29,320 So the multiply function defines two parameters, 19 00:02:29,320 --> 00:02:33,460 so we now have to provide two arguments when we call it. I'm going to 20 00:02:33,460 --> 00:02:38,680 to do that by entering those in the parentheses on line six: 10.5 comma 21 00:02:38,680 --> 00:02:43,000 and 4. Now that fixes the error, so it's now ready to run the program. 22 00:02:43,010 --> 00:02:45,880 So let's run the program, 23 00:02:46,260 --> 00:02:52,360 and unsurprisingly, we get 42.0 printed out again. Because we've used parameters, 24 00:02:52,360 --> 00:02:56,400 we can use our multiply function to multiply different numbers. So as an 25 00:02:56,400 --> 00:03:05,300 example of that, we can type 42, 40 underscore 2, is equal to multiply, 26 00:03:05,300 --> 00:03:13,100 and we'll pass two arguments, 6 and 7 - 6 comma 7. Let's print it out to confirm it, print 42. 27 00:03:13,100 --> 00:03:16,060 Run the program. 28 00:03:17,000 --> 00:03:21,410 This time we've got 42 printed out as an integer. When you multiply two ints, the 29 00:03:21,410 --> 00:03:26,270 result is int. We can use our multiply function in a loop, as well. In fact, we 30 00:03:26,270 --> 00:03:31,100 can use it anywhere that Python expects an expression. A function call is another 31 00:03:31,100 --> 00:03:35,210 type of expression. Let's put some more code in here. What I'm going to do is, 32 00:03:35,210 --> 00:03:42,940 close down the output pane. Line 12, I'm going to print an empty line, then line 14, 33 00:03:42,940 --> 00:03:50,780 for val in range, parentheses 1 comma 5 closing parenthesis and a colon. We're 34 00:03:50,780 --> 00:03:57,220 going to put two underscore times is equal to multiply, and in parentheses, 35 00:03:57,220 --> 00:04:08,400 two comma vowel. Then on the next line, we'll print two_times. Run this program now, 36 00:04:11,160 --> 00:04:15,020 and you can see what's happened there - our loop has multiplied the values from 1 to 4 37 00:04:15,020 --> 00:04:20,200 by 2. As you can see, multiply is now a little bit more useful. We can tell it 38 00:04:20,200 --> 00:04:24,160 which two numbers to multiply and it returns the result. It's still not a very 39 00:04:24,160 --> 00:04:27,760 exciting function, but it does demonstrate how the formal parameters 40 00:04:27,760 --> 00:04:32,260 are given values, by the arguments that we pass when calling the function. 41 00:04:32,260 --> 00:04:35,980 In the next video, we'll run the program in the debugger, and see how the arguments 42 00:04:35,980 --> 00:04:42,000 are used in place of the formal parameters. See you in the next video.