1
00:00:00,000 --> 00:00:03,000
Let's take a look at multiple comparison operators

2
00:00:03,000 --> 00:00:04,200
within an 'if' statement.

3
00:00:04,200 --> 00:00:10,000
So in the last two videos I said, if something is True, do a thing.

4
00:00:10,000 --> 00:00:12,800
So I am just going to write 'pass', because indentation is important.

5
00:00:12,800 --> 00:00:16,600
If we just wrote 'if True', we're going to see 'SyntaxError',

6
00:00:16,600 --> 00:00:18,400
so we just write 'pass'

7
00:00:18,450 --> 00:00:21,570
if we don't want anything to happen. And this will evaluate.

8
00:00:21,580 --> 00:00:23,310
Python will say, "Yep, this works.

9
00:00:23,370 --> 00:00:26,130
So I'm going to execute whatever code is indented in here".

10
00:00:26,240 --> 00:00:29,570
But what if we want to look up two things at the same time?

11
00:00:29,700 --> 00:00:34,900
What we could do, 'course = "Python for Everybody"',

12
00:00:34,920 --> 00:00:41,510
and we could also set the 'student', name '= "Ezra"'.

13
00:00:42,140 --> 00:00:43,550
And so now we can compare these.

14
00:00:43,550 --> 00:00:49,500
We can say 'if course == "Python for Everybody"',

15
00:00:50,500 --> 00:00:54,400
and then we can nest it in here and say 'if student ==

16
00:00:54,900 --> 00:00:57,100
"Ezra": print(

17
00:00:58,500 --> 00:01:00,900
"Welcome to p4e,

18
00:01:02,500 --> 00:01:08,700
Ezra")' And it works because 'course' is "Python for Everybody",

19
00:01:09,000 --> 00:01:15,400
'student' is "Ezra". We have now successfully nested an 'if' statement,

20
00:01:15,470 --> 00:01:17,390
but we can actually merge these together.

21
00:01:17,400 --> 00:01:18,680
This is really easy, too.

22
00:01:18,680 --> 00:01:23,940
So if we just pull this up to this line here and write the

23
00:01:23,950 --> 00:01:27,840
word, 'and', so 'if course == "Python for Everybody"

24
00:01:27,840 --> 00:01:32,300
and if student = "Ezra": "Welcome to the course".

25
00:01:32,300 --> 00:01:34,600
I'll just change the text just to prove that this will work.

26
00:01:34,700 --> 00:01:38,600
And yep, I made a syntax error.

27
00:01:38,600 --> 00:01:40,000
And let's run that. There we go.

28
00:01:40,080 --> 00:01:42,470
So you don't need two 'if' statements in there, that's actually,

29
00:01:42,480 --> 00:01:43,580
I'm glad that one came up.

30
00:01:43,670 --> 00:01:47,940
So it's just 'if' your statement, and some other statement, is

31
00:01:47,950 --> 00:01:52,480
True. Now what this is a lot like saying, is saying, 'if True

32
00:01:52,480 --> 00:01:59,800
and True, do a thing, and we can actually 'print("Do a thing")'

33
00:01:59,830 --> 00:02:01,630
just to make sure that this is working.

34
00:02:01,640 --> 00:02:04,870
So this one is True, and this statement here is True, and

35
00:02:04,880 --> 00:02:07,660
that 'and' operator is saying that both of them need to be True.

36
00:02:07,900 --> 00:02:10,360
Now we can actually swap this out entirely.

37
00:02:10,370 --> 00:02:13,090
We can say that only one of them needs to be True. With the

38
00:02:13,100 --> 00:02:14,700
'and' statement they both need to be True.

39
00:02:14,780 --> 00:02:17,750
And you can put as many 'and' statements together as you want.

40
00:02:17,920 --> 00:02:21,580
But if you only wanted one of these to be True, you could

41
00:02:21,590 --> 00:02:24,760
say either the 'course' is "Python for Everybody", or the 'student'

42
00:02:24,770 --> 00:02:26,830
is "Ezra", "Welcome to the course,

43
00:02:26,840 --> 00:02:30,220
Ezra". It's not necessarily what we're looking for anymore, because

44
00:02:30,220 --> 00:02:32,700
the 'student' might not be "Ezra", they just might be in the

45
00:02:32,700 --> 00:02:33,700
Python course.

46
00:02:33,730 --> 00:02:40,990
So say, "You are either in Python for Everybody, or you are

47
00:02:41,170 --> 00:02:44,860
Ezra". Okay. Now let's go ahead and change this.

48
00:02:44,860 --> 00:02:49,200
Let's change this to something that we know is going to evaluate as False.

49
00:02:49,200 --> 00:02:53,320
But Ezra is still going to stay the same, and that still

50
00:02:53,330 --> 00:02:57,180
works. And if we get rid of this, it doesn't work.

51
00:02:57,180 --> 00:03:01,000
And so what this statement is saying is if something is True,

52
00:03:01,020 --> 00:03:04,080
or something else is True, just one of them needs to match.

53
00:03:04,300 --> 00:03:06,700
And I was going to undo that. Rerun that.

54
00:03:07,100 --> 00:03:13,200
Alright, let's check out a more complicated type of 'if' statements in here.

55
00:03:13,240 --> 00:03:16,540
So this 'if' statement is going to look for one of two things

56
00:03:16,550 --> 00:03:17,680
or something else.

57
00:03:17,690 --> 00:03:19,000
Actually, that's wrong.

58
00:03:19,010 --> 00:03:19,960
I explained that wrong.

59
00:03:19,970 --> 00:03:24,350
It's going to look for a True statement and a True statement,

60
00:03:24,360 --> 00:03:26,480
or another True statement.

61
00:03:26,860 --> 00:03:31,100
And so we can actually split these out by wrapping parentheses

62
00:03:31,100 --> 00:03:33,290
around these. So this is going to get a little bit wild,

63
00:03:33,300 --> 00:03:34,790
and I'll do my best to explain this,

64
00:03:34,800 --> 00:03:37,430
and hopefully this turns out pretty well in the video.

65
00:03:37,430 --> 00:03:41,400
So we've got 'course', 'student', and let's put a 'grade' in here.

66
00:03:42,200 --> 00:03:46,300
So let's just say the 'grade' is going to be, I don't know, grade 12.

67
00:03:46,360 --> 00:03:52,840
So now we can say 'if', with parentheses in here 'student

68
00:03:53,020 --> 00:03:59,920
== "Ezra" and 'course == "Python for everybody")

69
00:04:00,200 --> 00:04:06,400
or grade == 12: print("Success")'.

70
00:04:06,440 --> 00:04:08,600
And sure enough, this is going to show up.

71
00:04:08,610 --> 00:04:12,600
Now, that's because all of these are True. This is True and

72
00:04:12,600 --> 00:04:13,700
this is True.

73
00:04:13,740 --> 00:04:16,560
And because these are together in parentheses, they both

74
00:04:16,570 --> 00:04:17,459
have to be True.

75
00:04:17,470 --> 00:04:21,180
If one fails, this whole thing fails, everything inside the

76
00:04:21,190 --> 00:04:21,959
parentheses fails.

77
00:04:21,959 --> 00:04:23,100
That comes back as False.

78
00:04:23,100 --> 00:04:28,000
And even if that is False, it's going to say, 'or grade == 12'.

79
00:04:28,000 --> 00:04:29,900
So this is a lot like saying,

80
00:04:29,900 --> 00:04:31,900
[no audio]

81
00:04:31,900 --> 00:04:32,900
'if (True

82
00:04:32,900 --> 00:04:35,100
[no audio]

83
00:04:35,100 --> 00:04:39,100
and True) or, 'grade

84
00:04:39,100 --> 00:04:40,500
== 12', True.

85
00:04:40,580 --> 00:04:41,750
So here's the thing.

86
00:04:41,750 --> 00:04:43,200
One of these can fail.

87
00:04:43,200 --> 00:04:45,200
[no audio]

88
00:04:45,200 --> 00:04:48,100
If there is a True and False, this one, it's gone.

89
00:04:49,300 --> 00:04:50,700
Python says, "Get rid of it,

90
00:04:50,880 --> 00:04:53,610
but let's see if there is an or statement in there".

91
00:04:53,620 --> 00:04:55,620
And if there was an 'or' statement, which was True, this is

92
00:04:55,630 --> 00:04:57,880
going to boil down to 'print("Success")'.

93
00:04:57,890 --> 00:05:02,340
So let's just undo that, and change a few variables in here.

94
00:05:02,500 --> 00:05:04,900
Let's change "Ezra" to nothing, "".

95
00:05:04,900 --> 00:05:06,760
So we know that this is going to be False.

96
00:05:08,100 --> 00:05:10,500
This one here is going to be False, but this is still going

97
00:05:10,520 --> 00:05:13,040
to be True, and 'grade == 12', is going to be 'True'.

98
00:05:14,200 --> 00:05:18,000
So let's rerun each of these cells, still works.

99
00:05:18,080 --> 00:05:22,100
'If grade = 11', let's go ahead and change.

100
00:05:22,110 --> 00:05:23,790
This no longer works.

101
00:05:23,800 --> 00:05:24,990
Nothing shows up in there.

102
00:05:25,000 --> 00:05:28,800
And that's because one of these was False, and this one was

103
00:05:28,810 --> 00:05:33,460
False. So neither this one nor this grouped 'if' statement was

104
00:05:33,470 --> 00:05:39,080
True, and because nothing in there was True, when it came to

105
00:05:39,090 --> 00:05:42,380
this 'or' statement, this code was not executed.

106
00:05:42,390 --> 00:05:44,240
Now that's a little more complicated.

107
00:05:44,240 --> 00:05:46,800
You don't really have to fully understand how that works right now

108
00:05:46,860 --> 00:05:49,190
If you're brand new to programming, that's going to be a

109
00:05:49,250 --> 00:05:50,270
little bit confusing.

110
00:05:50,280 --> 00:05:52,490
But you are going to see things like this in the wild.

111
00:05:52,500 --> 00:05:55,040
But over time it does get a little bit easier to understand

112
00:05:55,050 --> 00:05:57,740
this. Now when these get really, really, really big, that

113
00:05:57,750 --> 00:05:58,880
gets very complicated.

114
00:05:58,890 --> 00:06:02,940
And we use a lot more nesting with just simple parentheses.

115
00:06:02,950 --> 00:06:04,380
So just go ahead,

116
00:06:04,380 --> 00:06:05,820
and there we go.

117
00:06:05,830 --> 00:06:07,800
I just undid my work there.

118
00:06:07,940 --> 00:06:10,760
So that's how we work with multiple comparison operators

119
00:06:10,770 --> 00:06:14,660
when it comes to the 'or' statement, or the 'and' statement, we

120
00:06:14,670 --> 00:06:15,500
can do either one.

121
00:06:15,510 --> 00:06:17,870
And in here we can group these together to make sure that

122
00:06:17,880 --> 00:06:19,250
both of these need to be True.

123
00:06:19,250 --> 00:06:23,000
If one of them is not True, this whole thing results in False,

124
00:06:23,020 --> 00:06:26,440
and then it looks for 'if grade == 12', 'if grade == 12',

125
00:06:26,450 --> 00:06:27,400
then it would be True.

126
00:06:27,400 --> 00:06:29,300
But actually, it would look like that.

127
00:06:29,300 --> 00:06:32,000
Now it's saying 'if False or True',

128
00:06:32,000 --> 00:06:35,800
and if we just run this in our interpreter, we can say True

129
00:06:35,800 --> 00:06:38,500
or False, comes back as True.

130
00:06:38,540 --> 00:06:42,150
False or true, also comes back as True,

131
00:06:42,150 --> 00:06:44,250
because True is in there with an 'or' statement

132
00:06:44,250 --> 00:06:45,400
it always comes back.

133
00:06:45,400 --> 00:06:48,150
We can do the opposite as well with an 'and' statement.

134
00:06:48,160 --> 00:06:51,570
So 'True and False', one of them is not True,

135
00:06:51,630 --> 00:06:52,770
it turns out False.

136
00:06:52,940 --> 00:06:55,130
We can do the opposite as well.

137
00:06:55,130 --> 00:06:57,200
False and True, again,

138
00:06:57,260 --> 00:06:58,370
one of those is False,

139
00:06:58,380 --> 00:06:59,750
it's going to return False.

140
00:06:59,750 --> 00:07:02,600
It's always looking for Tuue all the way through.

141
00:07:02,600 --> 00:07:04,400
Hey, that rhymed. I'm going to start using that.

142
00:07:04,460 --> 00:07:06,280
It's always looking for True all the way through.

143
00:07:06,280 --> 00:07:08,040
So I'm going to undo that.

144
00:07:08,050 --> 00:07:11,100
And that is multiple comparison operators.

145
00:07:11,110 --> 00:07:13,470
So when you're learning this honestly, just start small.

146
00:07:13,620 --> 00:07:17,850
Say if one thing is something and another thing is something,

147
00:07:17,850 --> 00:07:20,460
and then you can make it a little more complicated.

148
00:07:20,470 --> 00:07:23,100
And you can say if something is something and something else

149
00:07:23,110 --> 00:07:24,180
is not something.

150
00:07:24,360 --> 00:07:28,050
But for now, like always, take it slow, take it easy,

151
00:07:28,050 --> 00:07:30,270
and over time, this just becomes second nature.