1
00:00:00,234 --> 00:00:01,940
Hi guys, and welcome back!

2
00:00:01,940 --> 00:00:04,700
In this video, we'll learn about getting user input

3
00:00:04,700 --> 00:00:05,910
so that we can get some data

4
00:00:05,910 --> 00:00:08,783
from our users and use it in our programmes.

5
00:00:09,700 --> 00:00:12,200
Let's start off by asking the user for their name,

6
00:00:12,200 --> 00:00:13,510
so we can print it out.

7
00:00:13,510 --> 00:00:16,410
We will say name equals, and again,

8
00:00:16,410 --> 00:00:18,360
this is us defining a variable.

9
00:00:18,360 --> 00:00:20,390
Now, we have to tell the variable what its

10
00:00:20,390 --> 00:00:21,800
value is going to be.

11
00:00:21,800 --> 00:00:23,620
So what we're gonna do here is we're going to

12
00:00:23,620 --> 00:00:26,630
ask the user for their name.

13
00:00:26,630 --> 00:00:28,690
And the way we do that in Python is we type,

14
00:00:28,690 --> 00:00:30,820
input, then a pair of brackets,

15
00:00:30,820 --> 00:00:33,680
and inside the brackets we are gonna type a question

16
00:00:33,680 --> 00:00:36,200
that we'll ask the user or a prompt.

17
00:00:36,200 --> 00:00:40,710
So here, goes a string where we put enter your name.

18
00:00:40,710 --> 00:00:42,650
So here, we're calling another function.

19
00:00:42,650 --> 00:00:44,275
Just like the print function.

20
00:00:44,275 --> 00:00:45,290
But in this case,

21
00:00:45,290 --> 00:00:48,865
this function here will print this prompt out.

22
00:00:48,865 --> 00:00:53,550
And then, it will wait for the user to type and press enter.

23
00:00:53,550 --> 00:00:56,450 line:15% 
Then, we're gonna print out the name.

24
00:00:56,450 --> 00:00:57,860 line:15% 
So, I've run this code here,

25
00:00:57,860 --> 00:01:00,570 line:15% 
and you can see that we get asked to enter our name.

26
00:01:00,570 --> 00:01:02,400 line:15% 
I'm gonna type here, Rolf.

27
00:01:02,400 --> 00:01:04,670 line:15% 
And then, Rolf comes back out.

28
00:01:04,670 --> 00:01:08,350 line:15% 
So, this is how you can ask the user for their name,

29
00:01:08,350 --> 00:01:10,260
or indeed, any other piece of data.

30
00:01:10,260 --> 00:01:12,323
And then, use it in your programmes.

31
00:01:13,370 --> 00:01:16,440
If you wanted to ask the user for a value

32
00:01:16,440 --> 00:01:18,620
that you want to do mathematics on,

33
00:01:18,620 --> 00:01:20,750
then there is something important to take into account

34
00:01:20,750 --> 00:01:22,390
when you're coding in Python.

35
00:01:22,390 --> 00:01:25,740
And that is that the input function always

36
00:01:25,740 --> 00:01:27,710
gives you back a string.

37
00:01:27,710 --> 00:01:30,580
So, this input will ask the user for a value,

38
00:01:30,580 --> 00:01:32,275
and it will give you a string.

39
00:01:32,275 --> 00:01:36,408
Now, remember that you can't do mathematics on strings

40
00:01:36,408 --> 00:01:39,360
in the same way that you can with numbers.

41
00:01:39,360 --> 00:01:41,210
So, if you wanted to calculate the amount

42
00:01:41,210 --> 00:01:43,440
of square metres that is the equivalent

43
00:01:43,440 --> 00:01:45,770
to the size of their house in square feet,

44
00:01:45,770 --> 00:01:49,030
you would do size input, divided by ten point eight.

45
00:01:49,030 --> 00:01:51,210
That's more or less the right number.

46
00:01:51,210 --> 00:01:53,530
And then, you can print square metres.

47
00:01:53,530 --> 00:01:56,410
But, remember that you can't do maths that well.

48
00:01:56,410 --> 00:01:57,620
So, if I save this,

49
00:01:57,620 --> 00:01:59,633
and then I go ahead and run it,

50
00:02:00,662 --> 00:02:05,060 line:15% 
and I ask for example my size is 500 square feet,

51
00:02:05,060 --> 00:02:06,380 line:15% 
you're gonna get an error.

52
00:02:06,380 --> 00:02:09,030 line:15% 
And you can see here that you've got a type error,

53
00:02:09,030 --> 00:02:09,863 line:15% 
and it says,

54
00:02:09,863 --> 00:02:12,790 line:15% 
unsupported operand types for the division

55
00:02:12,790 --> 00:02:14,800 line:15% 
string and float.

56
00:02:14,800 --> 00:02:16,490
So, what this is saying basically is that

57
00:02:16,490 --> 00:02:20,060
we've tried dividing a string by a float,

58
00:02:20,060 --> 00:02:21,800
and you can't do that.

59
00:02:21,800 --> 00:02:25,860
So, we need to convert this into a number

60
00:02:25,860 --> 00:02:27,570
instead of a string.

61
00:02:27,570 --> 00:02:29,162
So, what we've got to do is we have to

62
00:02:29,162 --> 00:02:32,920
first turn this size input into a number.

63
00:02:32,920 --> 00:02:34,240
So, what I'm gonna do is I'm gonna define

64
00:02:34,240 --> 00:02:35,880
a variable called square feet,

65
00:02:35,880 --> 00:02:39,170
and I'm gonna say "int" of size input.

66
00:02:39,170 --> 00:02:40,720
And what this is doing is it's

67
00:02:40,720 --> 00:02:43,230
doing something like what we had before.

68
00:02:43,230 --> 00:02:47,950
We are passing size input into another function,

69
00:02:47,950 --> 00:02:49,530
which is this int.

70
00:02:49,530 --> 00:02:51,860
And that is going to try to turn our string

71
00:02:51,860 --> 00:02:54,290
into an integer, a whole number.

72
00:02:54,290 --> 00:02:56,820
So that we can then do maths on it.

73
00:02:56,820 --> 00:02:59,060
Notice that here in our square metres line,

74
00:02:59,060 --> 00:03:00,520
we're still using size input,

75
00:03:00,520 --> 00:03:02,080
which is our string.

76
00:03:02,080 --> 00:03:04,270
If we wanna make sure that we use the number,

77
00:03:04,270 --> 00:03:07,030
we must use this square feet variable

78
00:03:07,030 --> 00:03:08,940
that we've defined on line two.

79
00:03:08,940 --> 00:03:11,853
Otherwise, that means we're still using the string.

80
00:03:12,970 --> 00:03:15,283
Let's save this and then run it.

81
00:03:16,230 --> 00:03:18,060 line:15% 
So here, we've got this app running,

82
00:03:18,060 --> 00:03:19,520 line:15% 
and I'm gonna type in 500.

83
00:03:19,520 --> 00:03:22,410 line:15% 
And now we get 46.3.

84
00:03:22,410 --> 00:03:24,440
So here's a small challenge for you.

85
00:03:24,440 --> 00:03:26,750
Try to print something a little bit nicer,

86
00:03:26,750 --> 00:03:28,770
rather than just this square metres.

87
00:03:28,770 --> 00:03:30,850
For example, you could print something like,

88
00:03:30,850 --> 00:03:33,300
this number of square feet is equal to this number

89
00:03:33,300 --> 00:03:34,313
of square metres.

90
00:03:35,760 --> 00:03:37,950
I'd recommend pausing the video and giving it a go.

91
00:03:37,950 --> 00:03:40,470
But, I'll try and do it right now as well.

92
00:03:40,470 --> 00:03:41,910
We're gonna use an "f" string.

93
00:03:41,910 --> 00:03:43,510
So I will type the f-key,

94
00:03:43,510 --> 00:03:45,300
and then the double quotation marks,

95
00:03:45,300 --> 00:03:46,133
and inside it,

96
00:03:46,133 --> 00:03:48,383
I'm gonna use my square feet variable,

97
00:03:49,370 --> 00:03:53,555
and type square feet, square feet is square metres,

98
00:03:53,555 --> 00:03:55,373
square metres.

99
00:03:56,960 --> 00:03:59,850
Notice that this here is the variable

100
00:03:59,850 --> 00:04:02,530
that we wanna put the value of inside our string.

101
00:04:02,530 --> 00:04:05,780
So, we still have to say what that variable means.

102
00:04:05,780 --> 00:04:10,780
So, for example, 500 square feet is 46 square metres.

103
00:04:12,490 --> 00:04:14,010 line:15% 
So, if we run this again,

104
00:04:14,010 --> 00:04:16,330 line:15% 
you'll see that as soon I type a 500,

105
00:04:16,330 --> 00:04:17,860 line:15% 
we get a nicer input.

106
00:04:17,860 --> 00:04:20,603 line:15% 
500 square feet is 46 square metres.

107
00:04:21,710 --> 00:04:24,580
If you want to format a floating point number,

108
00:04:24,580 --> 00:04:27,970
so that you only get a certain number of digits at the end,

109
00:04:27,970 --> 00:04:30,590
you can do point two f, for example.

110
00:04:30,590 --> 00:04:32,840
So here, what we've got is a slightly more obscure

111
00:04:32,840 --> 00:04:33,770
piece of syntax.

112
00:04:33,770 --> 00:04:38,770
We've got square metres colon point two f.

113
00:04:38,947 --> 00:04:40,260
And what that does,

114
00:04:40,260 --> 00:04:44,380
is it will try to format this square metres

115
00:04:44,380 --> 00:04:46,580
with two decimal places only.

116
00:04:46,580 --> 00:04:48,900
This is what this piece of syntax means.

117
00:04:48,900 --> 00:04:49,770 line:15% 
So, I'm gonna save that,

118
00:04:49,770 --> 00:04:51,350 line:15% 
run it again,

119
00:04:51,350 --> 00:04:56,350 line:15% 
and now you see we get 46.30 square metres.

120
00:04:56,770 --> 00:04:59,550
If you want to learn more about this formatting syntax,

121
00:04:59,550 --> 00:05:02,030
I'm gonna leave a link in the resources section

122
00:05:02,030 --> 00:05:02,863
of this lecture,

123
00:05:02,863 --> 00:05:04,330
or on the description below,

124
00:05:04,330 --> 00:05:05,898
so that you can have a read of that.

125
00:05:05,898 --> 00:05:07,440
Well, that's everything for this video.

126
00:05:07,440 --> 00:05:09,480
We've learned how to get user input,

127
00:05:09,480 --> 00:05:11,330
and how to turn it into a number,

128
00:05:11,330 --> 00:05:12,986
in case we need to do maths on it.

129
00:05:12,986 --> 00:05:14,690
Thanks for joining me in this one,

130
00:05:14,690 --> 00:05:16,340
and I'll see you in the next one.