1 00:00:00,400 --> 00:00:05,320 Now in this lesson, I want to talk to you about Python variables and it's a 2 00:00:05,320 --> 00:00:09,220 really, really useful concept. But before we get started, 3 00:00:09,370 --> 00:00:14,370 first I want you to head over to the course resources and get hold of the Day 4 00:00:15,820 --> 00:00:20,820 1 variables start Repl.it sandbox or you can simply type the URL into the 5 00:00:22,330 --> 00:00:23,163 browser. 6 00:00:23,380 --> 00:00:28,380 I want you to first go ahead and fork this starting code so that you can work on 7 00:00:28,750 --> 00:00:31,990 your own version of it. Now once you've done that, 8 00:00:32,140 --> 00:00:37,140 then the first thing I want to do is to take a look at this line of code that 9 00:00:37,930 --> 00:00:41,830 you should have already. And when we run this, 10 00:00:41,860 --> 00:00:44,260 we should be pretty familiar with what happens, right? 11 00:00:44,260 --> 00:00:48,700 It will ask us for our name and when we hit enter, nothing happens. 12 00:00:49,060 --> 00:00:50,770 But behind the scenes, 13 00:00:51,160 --> 00:00:56,160 this name or this input has now been received by this function. 14 00:00:57,550 --> 00:01:02,020 But once that's done, it kind of just disappears, right? 15 00:01:02,680 --> 00:01:07,680 And there's no way for us to be able to refer to it in the future. Or is there? 16 00:01:10,980 --> 00:01:13,920 Well, this is where variables come in really handy. 17 00:01:14,520 --> 00:01:18,150 If I give the results of this action a name, 18 00:01:18,390 --> 00:01:20,940 well then I'll be able to refer to it later on. 19 00:01:21,540 --> 00:01:23,850 So at the beginning of the line, 20 00:01:23,940 --> 00:01:27,630 I'm going to call it name and then I'm going to add an equal sign 21 00:01:28,170 --> 00:01:33,170 and what this does is it assigns whatever it is that the user typed in as the 22 00:01:33,600 --> 00:01:38,600 input to this prompt to a variable called name. 23 00:01:40,350 --> 00:01:45,350 So now if I go ahead and run my code again and I enter a name, 24 00:01:47,970 --> 00:01:49,980 now once I hit enter, 25 00:01:50,040 --> 00:01:53,910 normally there's no way for me to get hold of this anymore, right? 26 00:01:54,480 --> 00:01:58,800 But now I can actually go ahead and write print. 27 00:01:59,220 --> 00:02:02,580 I'm going to print the value of this variable name. 28 00:02:03,300 --> 00:02:07,170 So now if I run my code and I write a name, 29 00:02:07,560 --> 00:02:08,393 hit enter, 30 00:02:08,759 --> 00:02:13,760 you'll see that this gets printed and I can use this at any point in my code 31 00:02:14,760 --> 00:02:19,760 just by referring to the name that's attached to this value. 32 00:02:21,510 --> 00:02:26,510 So it's almost like we've saved the data from this action to a name. 33 00:02:29,760 --> 00:02:33,660 And if you think about it, if you had a phone book, let's say, 34 00:02:33,660 --> 00:02:37,080 and you just jotted down the numbers of people, 35 00:02:37,560 --> 00:02:39,120 the next time you look at this, 36 00:02:39,150 --> 00:02:43,110 there's no way for you to know who's number that is, right? 37 00:02:43,740 --> 00:02:46,560 In a sense it's the same thing with the computer. 38 00:02:47,100 --> 00:02:50,160 Even though we've inputted this piece of data, 39 00:02:50,310 --> 00:02:55,310 there's no way for us to be able to refer to this data unless we give it a name. 40 00:02:56,760 --> 00:03:01,760 So in our phone book, we might say that this particular number is associated with 41 00:03:02,410 --> 00:03:07,410 the name James. And in programming we would call this name James a variable. 42 00:03:09,400 --> 00:03:14,400 So we could write something like James equals and then his phone number. 43 00:03:15,400 --> 00:03:19,360 And this means that in the future, if we ever need this piece of data, 44 00:03:19,570 --> 00:03:22,480 we can just refer to it by its name, 45 00:03:23,020 --> 00:03:25,900 the variable name of James. Now, 46 00:03:25,960 --> 00:03:28,750 as the name variable suggests, 47 00:03:29,470 --> 00:03:33,670 it's something that can be changed or can be varied. 48 00:03:34,270 --> 00:03:35,530 So for example, 49 00:03:35,650 --> 00:03:40,480 just because this name is set to something up here doesn't mean that I can't 50 00:03:40,480 --> 00:03:43,840 change it later on. So to make things simple, 51 00:03:43,840 --> 00:03:48,610 let's go ahead and delete the input function and let's just say name is equal to 52 00:03:48,610 --> 00:03:50,110 Jack. Print name. 53 00:03:50,320 --> 00:03:55,320 When I run that Jack is what gets printed inside the console because I'm now 54 00:03:55,720 --> 00:03:59,290 referring to that piece of data by the variable name. 55 00:04:00,100 --> 00:04:05,100 But if later on I decide to give this variable a different piece of data to hold 56 00:04:06,010 --> 00:04:06,843 on to, 57 00:04:07,000 --> 00:04:12,000 let's say Angela and I print name at this time point after I've changed it, 58 00:04:15,760 --> 00:04:18,850 what do you think these two lines will print? 59 00:04:19,450 --> 00:04:21,190 What do you think will first be printed? 60 00:04:21,250 --> 00:04:25,990 What do you think will be printed second? Let's hit command + enter or control + 61 00:04:25,990 --> 00:04:27,790 enter and see for ourselves. 62 00:04:28,390 --> 00:04:33,390 So even though they're both printing the same variable, at this point when we first 63 00:04:34,810 --> 00:04:38,080 call print, it's holding on to the value of Jack,. 64 00:04:38,500 --> 00:04:43,500 But by line 5 I've now changed it so that it's holding onto the value of 65 00:04:43,780 --> 00:04:44,613 Angela. 66 00:04:45,550 --> 00:04:50,550 This makes it a lot easier when we want to write code like what we did before. 67 00:04:51,250 --> 00:04:51,880 For example, 68 00:04:51,880 --> 00:04:55,750 this is the line of code that we had before and we knew that we were going to 69 00:04:55,750 --> 00:05:00,750 get a piece of data from this input function and then we would calculate a new 70 00:05:02,050 --> 00:05:04,510 piece of data using the Len function 71 00:05:04,990 --> 00:05:07,540 and finally we're going to print everything out. 72 00:05:08,320 --> 00:05:12,670 Instead of having such a long line of code, which can be quite confusing, 73 00:05:13,120 --> 00:05:18,100 we can, if we wanted to, use variables to store each of these steps. 74 00:05:18,550 --> 00:05:19,390 So for example, 75 00:05:19,390 --> 00:05:24,390 we could say that the name was equal to whatever the user inserted as the 76 00:05:25,120 --> 00:05:25,953 input 77 00:05:26,530 --> 00:05:30,310 and then when we wanted to calculate the length, 78 00:05:30,730 --> 00:05:35,680 then we could set that variable to equal the Len function. 79 00:05:36,070 --> 00:05:41,070 And then inside the parentheses, we'll pass in the name, the value, that's stored 80 00:05:41,800 --> 00:05:45,580 in the name variable right here. And finally, 81 00:05:45,820 --> 00:05:50,710 all that we need to do is to print the length, 82 00:05:53,620 --> 00:05:56,470 like so. So in this case, 83 00:05:56,840 --> 00:06:01,840 this data is stored under this name and then that data is what's going to be 84 00:06:02,360 --> 00:06:04,940 used in order to carry out this function 85 00:06:05,510 --> 00:06:08,780 and then the result will get stored in yet another variable 86 00:06:09,110 --> 00:06:11,360 and finally that variable will be printed out. 87 00:06:11,870 --> 00:06:16,870 So let's go ahead and run this code and type in my name. 88 00:06:17,090 --> 00:06:21,950 So Angela and hit enter and it does exactly the same thing, 89 00:06:22,460 --> 00:06:27,460 but now we've got all of these pieces of data all associated with a name that we 90 00:06:29,450 --> 00:06:34,160 can refer to at any later point in our code. Now it's time, 91 00:06:34,190 --> 00:06:36,560 you guessed it, for a code challenge. 92 00:06:36,860 --> 00:06:39,500 And I'm going to get you to apply what you've learned. 93 00:06:39,800 --> 00:06:42,860 So for all of that and more, I'll see you on the next lesson.