1
00:00:00,840 --> 00:00:03,570
Instructor: I wanna talk to you about another way

2
00:00:03,570 --> 00:00:05,790
to do conditional logic.

3
00:00:05,790 --> 00:00:10,023
We saw the if, elif, and then the else statement.

4
00:00:11,100 --> 00:00:15,633
But there's another way called the ternary operator.

5
00:00:17,250 --> 00:00:22,250
Now this is still the same as the else if or if else

6
00:00:22,830 --> 00:00:25,530
statements, but it's a shortcut.

7
00:00:25,530 --> 00:00:29,250
So, you can only use these on certain conditional logic.

8
00:00:29,250 --> 00:00:32,130
So, it doesn't mean that, hey this is just

9
00:00:32,130 --> 00:00:33,540
an entirely new way.

10
00:00:33,540 --> 00:00:35,610
This is a shortcut, in a sense,

11
00:00:35,610 --> 00:00:39,870
for you to make your code a little bit cleaner.

12
00:00:39,870 --> 00:00:41,040
Let's have a look.

13
00:00:41,040 --> 00:00:43,110
By the way, these ternary operators

14
00:00:43,110 --> 00:00:46,440
can also be called conditional expressions.

15
00:00:46,440 --> 00:00:48,900
And when you hear the word expression

16
00:00:48,900 --> 00:00:50,790
that should mean something to you, right?

17
00:00:50,790 --> 00:00:55,790
It's an expression because it evaluates to a value.

18
00:00:56,400 --> 00:01:00,870
So, a ternary operator, or a conditional expression,

19
00:01:00,870 --> 00:01:03,480
is an operation that evaluates to something

20
00:01:03,480 --> 00:01:06,630
based on the condition being true or not.

21
00:01:06,630 --> 00:01:10,530
And it's actually a new feature of Python as of version 2.4.

22
00:01:10,530 --> 00:01:12,180
So, let's have a look.

23
00:01:12,180 --> 00:01:16,173
The way we use this is to say, is condition,

24
00:01:17,070 --> 00:01:22,070
if this is true, then do this.

25
00:01:22,380 --> 00:01:25,410
So, this is the condition if true, and bear with me here,

26
00:01:25,410 --> 00:01:28,680
it is a little bit confusing at first.

27
00:01:28,680 --> 00:01:33,363
We say if, and here we give condition.

28
00:01:34,440 --> 00:01:39,440
Otherwise condition if else, all right?

29
00:01:41,340 --> 00:01:43,110
That is, that is a little confusing.

30
00:01:43,110 --> 00:01:44,373
So, let's go through it.

31
00:01:45,210 --> 00:01:49,140
So, the if is going to check this condition.

32
00:01:49,140 --> 00:01:51,240
So, it doesn't actually start with here.

33
00:01:51,240 --> 00:01:54,750
It's going to say, hey, if this condition.

34
00:01:54,750 --> 00:01:58,620
Now, this is going to evaluate to either true or false.

35
00:01:58,620 --> 00:02:01,980
If it's true, then we're going to do this.

36
00:02:01,980 --> 00:02:04,680
Otherwise we're going to do this.

37
00:02:04,680 --> 00:02:08,073
So, let me show you an example of how that would work.

38
00:02:10,110 --> 00:02:12,870
Let's say we're trying to determine if, well,

39
00:02:12,870 --> 00:02:16,017
if a user is your friend, so we'll say is_friend.

40
00:02:17,490 --> 00:02:21,120
And here we can set true or false for friend.

41
00:02:21,120 --> 00:02:24,990
Maybe we can check on Facebook if users can message you,

42
00:02:24,990 --> 00:02:27,510
or on Twitter, whether Twitter users

43
00:02:27,510 --> 00:02:30,180
can give you direct messages.

44
00:02:30,180 --> 00:02:33,643
Well, here, and let's do can_message,

45
00:02:36,300 --> 00:02:40,200
and here we can do our ternary operator.

46
00:02:40,200 --> 00:02:44,370
We're going to say, "Message allowed" if,

47
00:02:44,370 --> 00:02:46,890
so this is, if the condition is true,

48
00:02:46,890 --> 00:02:50,880
the condition is hey, is this person your friend?

49
00:02:50,880 --> 00:02:54,420
Otherwise condition that is false, well,

50
00:02:54,420 --> 00:02:59,337
I'm going to say, "Not allowed to message."

51
00:03:00,240 --> 00:03:02,550
And you can see here that this is a one liner,

52
00:03:02,550 --> 00:03:05,160
the, it looks like two lines but you can see over here

53
00:03:05,160 --> 00:03:08,490
that it's not really, it's just that we're wrapping

54
00:03:08,490 --> 00:03:09,990
so we can see the entire code.

55
00:03:11,370 --> 00:03:16,370
So, let's run this and see what can_message prints.

56
00:03:17,880 --> 00:03:22,880
If I run this, "message is allowed," because, well,

57
00:03:23,400 --> 00:03:27,720
we've assigned "message allowed" to can_message because,

58
00:03:27,720 --> 00:03:29,760
well, the condition was true.

59
00:03:29,760 --> 00:03:33,607
If this person wasn't my friend, and I run this,

60
00:03:33,607 --> 00:03:35,700
"not allowed to message."

61
00:03:35,700 --> 00:03:40,200
Because the condition, the if condition, evaluates to false.

62
00:03:40,200 --> 00:03:42,750
I know the ordering here can be a little bit confusing.

63
00:03:42,750 --> 00:03:45,870
So, you might have to look at it a couple of times

64
00:03:45,870 --> 00:03:50,340
and you do need to use it a few times to really remember it.

65
00:03:50,340 --> 00:03:52,890
But this is the general rule.

66
00:03:52,890 --> 00:03:57,890
Condition if true, if condition else, condition if-

67
00:03:58,080 --> 00:04:00,780
Not if else, if false.

68
00:04:00,780 --> 00:04:02,310
Can't spell.

69
00:04:02,310 --> 00:04:03,150
All right.

70
00:04:03,150 --> 00:04:07,770
A nice shorthand way to do something when a condition

71
00:04:07,770 --> 00:04:11,730
is either true or false, or evaluates to true or false.

72
00:04:11,730 --> 00:04:13,305
All right, I'll see you in the next video.

73
00:04:13,305 --> 00:04:14,193
Bye-bye.