1 00:00:04,630 --> 00:00:09,070 So the challenge was to process the values list that our code produced, and you 2 00:00:09,070 --> 00:00:13,480 can see that on screen. We need to replace each of the string values with a 3 00:00:13,480 --> 00:00:19,440 numeric equivalent, and just to recap, if I run this, there's the output down the bottom. 4 00:00:19,440 --> 00:00:23,540 So we've seen how to convert a string to an int, using the int function. 5 00:00:23,540 --> 00:00:28,780 The solution involves iterating over the list, and converting each value. There are 6 00:00:28,780 --> 00:00:32,360 a couple of ways you could do that, so I'm going to write the code for both of them. 7 00:00:32,360 --> 00:00:34,539 The first method we're going to look at, is to 8 00:00:34,539 --> 00:00:38,800 replace each value, in turn, with its integer equivalent. Let's have a go at 9 00:00:38,800 --> 00:00:45,200 doing that. I'm gonna start on line 29, with a comment - this is the first option - 10 00:00:45,200 --> 00:00:53,320 to replace the value, or the values, in place. The actual code will be for index 11 00:00:53,320 --> 00:00:59,220 in range, left parenthesis len left parenthesis values_list, 12 00:00:59,220 --> 00:01:04,519 two right parentheses and a colon. Then values_list left square bracket, 13 00:01:04,519 --> 00:01:11,460 index right square bracket, is equal to int left parenthesis value_list, 14 00:01:11,460 --> 00:01:14,860 then our left square bracket again, index, 15 00:01:14,860 --> 00:01:25,200 right square bracket and right parenthesis. Then line 33, we'll print out values_list. 16 00:01:25,200 --> 00:01:29,620 So we're iterating over the range of indexes, from 0 to the length of the list. 17 00:01:29,620 --> 00:01:34,200 Remember that range doesn't include the final value. Our indexes will run from 0 18 00:01:34,210 --> 00:01:39,609 to 6, because the length of the list is 7. For each index value, we'll replace the 19 00:01:39,609 --> 00:01:45,189 item at that position with its integer value. So we run the program now - you 20 00:01:45,189 --> 00:01:49,119 should hopefully see the list will contain 7 ints, and we can see that's the 21 00:01:49,119 --> 00:01:52,179 case, there. Clearly we can see the previous list there, which was strings, 22 00:01:52,180 --> 00:01:57,800 and then the latest list there, down the bottom, which is a list of ints. 23 00:01:57,800 --> 00:02:03,399 I want to draw your attention to this warning on line 31. You can see there, I've got a 24 00:02:03,399 --> 00:02:07,689 warning about unexpected types, if I hover over it. Normally, you should pay 25 00:02:07,689 --> 00:02:11,650 attention to any warnings that your IDE will give you. Here, what we're doing is, 26 00:02:11,650 --> 00:02:16,960 we're accessing string items in the list, then assigning a new integer value. 27 00:02:16,960 --> 00:02:20,200 The checker's correctly determined that we're assigning an int to 28 00:02:20,200 --> 00:02:25,000 something that was a string. It's warning us, in case that's not what we intended. 29 00:02:25,000 --> 00:02:28,360 However, in this case, that's exactly what we intended. 30 00:02:28,360 --> 00:02:32,760 We're mutating the entire list - replacing all the strings with ints - so in this 31 00:02:32,770 --> 00:02:37,960 particular case, we can safely ignore that warning. But strangely, though, it's 32 00:02:37,960 --> 00:02:42,490 the word index that's been highlighted, and that can be confusing. That's not 33 00:02:42,490 --> 00:02:46,540 what it's complaining about, and we can see that, if I replace int, over here, 34 00:02:46,540 --> 00:02:53,000 with string. The other warning's gone, which shows that it was the integer value, 35 00:02:53,000 --> 00:02:56,460 on the right of the equals, that the checker objected to. 36 00:02:56,460 --> 00:03:00,310 Fortunately, strange results like this are very rare, but I just thought I'd 37 00:03:00,310 --> 00:03:04,940 warn you about it, so you don't spend hours trying to fix code that isn't broken. 38 00:03:04,940 --> 00:03:09,400 Most of the time - and I really do mean most of the time - the warnings 39 00:03:09,400 --> 00:03:13,120 will be accurate, so keep that in mind. Alright, so I'm going to undo that change and go 40 00:03:13,120 --> 00:03:17,500 back to our int. Run it again. We should have the same output. Right, so 41 00:03:17,500 --> 00:03:22,450 let's move on. Now the other thing you may have done, is instead, create a new 42 00:03:22,450 --> 00:03:30,060 list and append the integer values to it. So I'm going to go ahead and do that. 43 00:03:30,060 --> 00:03:34,239 We'll make a comment that this is the second method - this is creating a new list, 44 00:03:34,239 --> 00:03:38,560 or create a new list, will be our approach. So I'll start by calling the new list 45 00:03:38,560 --> 00:03:43,959 integer values, so integer_values equals an empty list, 46 00:03:43,960 --> 00:03:49,380 which is left and right square brackets. I'll use a for loop again, so for value 47 00:03:49,380 --> 00:03:56,540 in values_list : and then integer_values 48 00:03:56,540 --> 00:04:04,269 dot append left parenthesis, int, left parenthesis value, then two right closing 49 00:04:04,269 --> 00:04:12,000 parentheses. Then we'll print out the output on line 40, print integer_values. 50 00:04:12,000 --> 00:04:14,940 So this time, we're getting each item from the list. 51 00:04:14,950 --> 00:04:20,709 We're converting it to an int and appending it to the new list. So once again, run the 52 00:04:20,709 --> 00:04:25,240 program, and confirm that the new list contains only ints, and you can see on 53 00:04:25,240 --> 00:04:29,710 screen there, that that is the case. There are often several ways to do things, 54 00:04:29,710 --> 00:04:32,050 and you'll find that different ways will have different 55 00:04:32,050 --> 00:04:38,520 advantage's and disadvantages. So can you spot any advantages and disadvantages, 56 00:04:38,520 --> 00:04:43,270 with the two solutions on the screen there, now. If you're not sure, watch the 57 00:04:43,270 --> 00:04:47,889 earlier videos, on removing items from a list, again. Don't just think about the 58 00:04:47,889 --> 00:04:52,659 data we've got here - remember to consider when the list is very large. So I'd like 59 00:04:52,660 --> 00:04:58,100 you to think of one advantage, that the first for loop has over the second, 60 00:04:58,100 --> 00:05:03,789 and also one disadvantage. Now please don't ask for the answer in the Q&A. At some point 61 00:05:03,789 --> 00:05:07,479 in the course, when it's a relevant part of what we're discussing, I'll come back 62 00:05:07,479 --> 00:05:12,490 to this. Keeping you in suspense like this may seem mean, OK I guess it really 63 00:05:12,490 --> 00:05:18,129 is mean, but programming's not just about writing code. Often it's about asking the 64 00:05:18,129 --> 00:05:22,240 right questions. Having questions like this in the back of your mind, 65 00:05:22,240 --> 00:05:27,219 will really help you to choose the optimal way to write your code. Alright, so 66 00:05:27,219 --> 00:05:31,000 that's the end of lists, for now. We'll be using lists a lot, throughout the 67 00:05:31,000 --> 00:05:35,050 course. You'll see different ways that they can be useful and get plenty of 68 00:05:35,050 --> 00:05:38,889 practice using them. But moving on in the next video, we're going to look at 69 00:05:38,889 --> 00:05:44,250 another data type - tuples. See you in the next video.