1
00:00:11,770 --> 00:00:13,540
Hi, everybody, and welcome.

2
00:00:13,840 --> 00:00:20,500
I'm super excited to talk about inheritance in this picture, but before proceeding to explaining it,

3
00:00:20,620 --> 00:00:24,010
let's go over the topics that we have already covered.

4
00:00:24,040 --> 00:00:30,280
OK, so we have already covered lots of topics in this course, and we've been through a lot of difficulties

5
00:00:30,280 --> 00:00:33,220
and lots of explanations and logics and assignments.

6
00:00:33,790 --> 00:00:42,220
So we've been through variables, collections, if statements, loop's methods, classes and objects.

7
00:00:42,550 --> 00:00:49,660
And you have seen in the previous lectures that all of these topics come integrated in object oriented

8
00:00:49,660 --> 00:00:55,750
programming in Python and you would need to dominate all of them in order to use OPIS.

9
00:00:57,040 --> 00:01:03,910
I'm sure that it wasn't easy for you to understand all the topics and to practice a lot and to loosen

10
00:01:03,910 --> 00:01:05,470
long hours of lectures.

11
00:01:05,470 --> 00:01:11,310
But I'm sure if you did now, you can surely say that you are professionals in Python programming.

12
00:01:12,460 --> 00:01:17,680
We're going to dive deeper into object oriented programming in this lecture and we're going to discuss

13
00:01:17,680 --> 00:01:21,370
a sub topic of OAP, which is called Inheritance.

14
00:01:21,640 --> 00:01:27,750
Inheritance is basically a behavior which is inside OPIS.

15
00:01:27,910 --> 00:01:34,480
It can be used not only in Python but also in other OPIS enhanced languages such as Java.

16
00:01:36,340 --> 00:01:40,530
Basically, inheritance is allowed.

17
00:01:40,610 --> 00:01:45,490
It allows us to have a parent child relationship between classes.

18
00:01:45,970 --> 00:01:53,890
We're going to create two classes and one of them would be defined as the parent and the other one would

19
00:01:53,890 --> 00:01:55,420
be defined as the child.

20
00:01:56,770 --> 00:02:00,490
In all cases, in computers, not only programmers.

21
00:02:00,680 --> 00:02:08,020
In programming, a parent is something that gives something to the child.

22
00:02:08,020 --> 00:02:09,310
It's above the child.

23
00:02:09,880 --> 00:02:18,220
And also in this case, that relationship that we're going to have between these two classes that we're

24
00:02:18,220 --> 00:02:19,940
going to create is the following.

25
00:02:20,650 --> 00:02:25,900
But first, let's talk about real life definition before we dive into coding.

26
00:02:27,440 --> 00:02:30,820
Let's assume that we have a broad.

27
00:02:32,000 --> 00:02:39,260
Category in all war in our world, this, we can call it a vehicle, OK, a vehicle is not something

28
00:02:39,260 --> 00:02:40,220
specific.

29
00:02:40,700 --> 00:02:45,020
A vehicle can be basically several stuff, several things.

30
00:02:45,020 --> 00:02:47,320
It can be a private car, a truck, a bus.

31
00:02:47,370 --> 00:02:52,360
OK, so if a vehicle is like a broad name for lots of things.

32
00:02:53,390 --> 00:02:58,460
So in our lecture, we're going to create a class with the name vehicle.

33
00:02:59,280 --> 00:03:05,300
OK, and you can already understand that vehicle would be the parent class.

34
00:03:05,330 --> 00:03:10,610
OK, so we're going to have two classes in the same Python file, first one at the top.

35
00:03:11,300 --> 00:03:12,620
This is going to be a vehicle.

36
00:03:12,850 --> 00:03:13,270
Right?

37
00:03:13,920 --> 00:03:20,120
And then beneath it, we're going to create a separate class, which will be a child class, in our

38
00:03:20,120 --> 00:03:21,640
case, private car.

39
00:03:22,910 --> 00:03:24,740
So we're going to have these two classes.

40
00:03:24,740 --> 00:03:25,130
Right.

41
00:03:25,620 --> 00:03:28,010
And why do we have in common between them?

42
00:03:28,490 --> 00:03:33,290
OK, so in vehicle, we're going to defined two things.

43
00:03:34,280 --> 00:03:41,330
But before talking about these two things, let's talk about common ground between all vehicles.

44
00:03:41,840 --> 00:03:52,880
Can you agree with me that all vehicles have wheels, doors, steering wheel, fuel tank and other items

45
00:03:53,000 --> 00:03:53,570
as well?

46
00:03:53,610 --> 00:03:54,010
Right.

47
00:03:54,440 --> 00:04:04,310
So we're going to define one method and one property in the vehicle class, and then we're going to

48
00:04:04,310 --> 00:04:09,680
use an instance of an object of a child class.

49
00:04:10,460 --> 00:04:16,470
And this child class is going to use this method and a property that we declared in the vehicle.

50
00:04:16,530 --> 00:04:21,680
OK, so the property in the method would be declared here.

51
00:04:22,840 --> 00:04:28,910
But we're going to create a separate class private car and using instance of this private car.

52
00:04:28,930 --> 00:04:29,350
Are you going?

53
00:04:29,560 --> 00:04:35,680
We're going to use this method in property which we created inside the vehicle, which is the parent.

54
00:04:35,900 --> 00:04:38,190
So you have an certain inheritance here.

55
00:04:38,560 --> 00:04:46,000
We're using property and methods inside the vehicle, but we're using a private car to initiate them.

56
00:04:46,030 --> 00:04:56,560
OK, so basically all child classes would absorb all the methods and properties of the parent class.

57
00:04:57,010 --> 00:04:57,490
OK.

58
00:04:58,560 --> 00:05:02,560
Hold it for me for one second of this sentence, OK?

59
00:05:02,790 --> 00:05:08,760
Child classes would absorb the methods and properties of the parent class and this is what we're going

60
00:05:08,760 --> 00:05:09,510
to do now.

61
00:05:09,540 --> 00:05:18,900
OK, so before talking how to do it, we're just going to see this example right here.

62
00:05:19,050 --> 00:05:19,500
Right.

63
00:05:20,610 --> 00:05:27,330
And let's go deeply and talk about all the details we see here, as always, making you like a monstrous

64
00:05:27,330 --> 00:05:28,440
example like this.

65
00:05:28,710 --> 00:05:32,700
But then once we break it down into small details, it's not so scary.

66
00:05:32,700 --> 00:05:33,090
Right.

67
00:05:33,870 --> 00:05:35,440
So let's start from the beginning.

68
00:05:35,460 --> 00:05:37,780
Let's start from the outer structure.

69
00:05:37,800 --> 00:05:43,500
OK, so what you see here is going to appear in one python file, right?

70
00:05:44,160 --> 00:05:48,300
In one python module you see here, class vehicle.

71
00:05:48,990 --> 00:05:53,010
And then you have the Init method and you have engine status method.

72
00:05:53,310 --> 00:05:55,450
Already familiar with this box.

73
00:05:55,460 --> 00:05:55,760
Right.

74
00:05:55,770 --> 00:05:58,650
Is the same thing as we covered lots of times.

75
00:06:00,390 --> 00:06:03,780
And here in the bottom part you can see an additional class.

76
00:06:04,170 --> 00:06:06,840
The name is Class Private Car.

77
00:06:07,110 --> 00:06:07,500
Right.

78
00:06:07,890 --> 00:06:12,030
And inside here you can also see def in it and that's it.

79
00:06:12,370 --> 00:06:14,040
OK, that's in it and that's it.

80
00:06:14,580 --> 00:06:17,100
We're going to discuss these parts here in a second.

81
00:06:17,110 --> 00:06:21,900
OK, but in overall, you can see here a class init method.

82
00:06:22,170 --> 00:06:29,640
And down here at the bottom you can see instance of an object that belongs to private car class.

83
00:06:31,070 --> 00:06:36,930
And you can see here, initiation or execution off engine status method.

84
00:06:37,010 --> 00:06:44,480
OK, so you have class parents, you have additional class child, you have instance of an object,

85
00:06:44,960 --> 00:06:48,260
an execution of a method.

86
00:06:48,530 --> 00:06:50,270
Now, let's go into details.

87
00:06:50,570 --> 00:06:55,520
OK, so up on here, you can see class private car.

88
00:06:55,820 --> 00:07:00,110
And inside these round brackets, you can see I mentioned here the war.

89
00:07:00,120 --> 00:07:03,740
The vehicle vehicle is the name of this class right here.

90
00:07:04,400 --> 00:07:04,760
Right.

91
00:07:07,050 --> 00:07:13,520
Going by the notes here at the right, you can see inherits all methods of vehicle class.

92
00:07:14,700 --> 00:07:21,960
So once I'm having this class right here and I'm mentioning a name of a different class, basically

93
00:07:21,960 --> 00:07:24,150
mentioning the name of the parent class.

94
00:07:25,540 --> 00:07:34,510
Then once I'm creating an instance of an object which belongs to the child private car, I can use the

95
00:07:34,510 --> 00:07:36,370
engine status method.

96
00:07:37,370 --> 00:07:38,720
Which is up in here.

97
00:07:40,720 --> 00:07:48,790
By this instance, so without this vehicle words right here, this is not possible because engine status

98
00:07:48,790 --> 00:07:52,490
method belongs to this part, to this class right here.

99
00:07:52,720 --> 00:07:58,450
So how come I have an instance belonging to private car and I'm using the method that belongs to a different

100
00:07:58,450 --> 00:08:05,920
class simply by using the vehicle, which is the parent class inside these wrong brackets.

101
00:08:06,010 --> 00:08:08,840
So this is inheritance of methods.

102
00:08:09,280 --> 00:08:10,450
Simple as that.

103
00:08:12,430 --> 00:08:15,730
Not once we covered the inheritance of methods.

104
00:08:16,150 --> 00:08:18,470
Let's cover the inheritance of properties.

105
00:08:18,530 --> 00:08:23,410
OK, it's going to be a bit more complicated, but follow me closely and I'm sure that you will be just

106
00:08:23,410 --> 00:08:25,940
fine and we're going to understand it quickly.

107
00:08:26,640 --> 00:08:35,440
OK, so going inside this definite method of the child right here, you can see here, first of all,

108
00:08:35,440 --> 00:08:40,380
self that is engine running equals engine is engine running.

109
00:08:40,390 --> 00:08:41,410
This is very simple.

110
00:08:41,410 --> 00:08:46,500
We already familiar with the first car, with the first property right here.

111
00:08:47,890 --> 00:08:53,710
But then you can see here Super Brackett's that you need.

112
00:08:53,800 --> 00:08:55,640
And then is the engine running OK?

113
00:08:55,930 --> 00:08:58,680
This line right here is a bit weird.

114
00:08:58,690 --> 00:08:59,860
We haven't seen it before.

115
00:09:00,910 --> 00:09:09,060
And this basically means is that we're having this instance here, right?

116
00:09:09,520 --> 00:09:14,140
We passed a true boolean variable into it.

117
00:09:14,560 --> 00:09:15,910
You see the number one here.

118
00:09:18,170 --> 00:09:26,750
It's received up here inside the declaration, and then from here, it went into this property, which

119
00:09:26,750 --> 00:09:31,520
is number three, and also went to this number three as well.

120
00:09:32,920 --> 00:09:43,270
And this super Nenita phrase allows us to pass the variable from here up to the top to here and then

121
00:09:43,270 --> 00:09:47,050
inside here and then inside engine status.

122
00:09:49,730 --> 00:10:01,070
So by using this super unit phrase, once we execute engine status, OK, once we execute this method

123
00:10:02,360 --> 00:10:11,150
and remember, we're using instance of an object of private car, it goes up in here, but it asks for

124
00:10:11,150 --> 00:10:13,390
a variable self is engine running.

125
00:10:13,400 --> 00:10:15,170
Is it true or is it false?

126
00:10:15,200 --> 00:10:16,190
It asks us.

127
00:10:17,120 --> 00:10:22,100
But the variable was passed to private car to this part right here.

128
00:10:23,120 --> 00:10:27,650
And we need somehow from this part to pass it to this part to the parent.

129
00:10:29,200 --> 00:10:37,690
And this is possible only by super any trace, so by using the super elite phrase, once we execute

130
00:10:37,690 --> 00:10:46,030
a method that belongs to the parent, by using the super eenie phrase, we're also using the variable.

131
00:10:47,110 --> 00:10:47,760
Through.

132
00:10:49,230 --> 00:10:58,680
Which is pass from here to here to here, then up to the end of the parent and then goes inside the

133
00:10:58,680 --> 00:11:00,360
method once it's executed.

134
00:11:01,020 --> 00:11:01,530
All right.

135
00:11:04,080 --> 00:11:05,650
This is not very complicated.

136
00:11:05,670 --> 00:11:07,850
Let's go over it again, literally.

137
00:11:07,860 --> 00:11:08,270
All right.

138
00:11:09,660 --> 00:11:16,650
So first of all, private car class inherits method and a property from vehicle class.

139
00:11:16,680 --> 00:11:25,230
OK, we understand that private car, for instance, this for focus equals private car inherits one

140
00:11:25,230 --> 00:11:28,770
method and one property from vehicle, which is the parent.

141
00:11:29,280 --> 00:11:32,970
Private car is the child while the vehicle is the parent.

142
00:11:34,110 --> 00:11:39,810
By mentioning vehicle in the declaration of a private car class, we achieve that.

143
00:11:39,810 --> 00:11:47,760
All methods from vehicle can be used by instance of private car by writing vehicle here.

144
00:11:49,700 --> 00:11:57,950
We can use Ingeus engine status method, which belongs to the top class, but by riding the vehicle

145
00:11:58,190 --> 00:12:04,610
keywords here, we can use all vehicles methods with this instance, which belongs to private car.

146
00:12:06,920 --> 00:12:09,030
This regards to methods.

147
00:12:09,290 --> 00:12:12,530
Now let's talk about the parameters, their property.

148
00:12:14,410 --> 00:12:20,470
In the parent class, we use a variable that is called is engine running, OK, you can see is engine

149
00:12:20,470 --> 00:12:22,360
running here, here and then inside.

150
00:12:22,360 --> 00:12:24,400
The method here is engine running.

151
00:12:27,620 --> 00:12:35,140
All right, in order to pass the property from private car class, we need we use a super unit phrase,

152
00:12:35,180 --> 00:12:37,620
OK, so we have this method right here.

153
00:12:37,670 --> 00:12:41,960
This method uses engine running, but it belongs to vehicle class.

154
00:12:42,920 --> 00:12:45,470
Here we have an instance of private car.

155
00:12:45,950 --> 00:12:52,100
So we insert a here variable, but we need somehow from this in here to pass it to the parent.

156
00:12:52,670 --> 00:12:56,000
And we're we're achieving this by super unit phrase.

157
00:12:56,000 --> 00:13:03,860
So we pass from here to here and into the method and it gets through here once we once we execute the

158
00:13:03,860 --> 00:13:04,730
engine status.

159
00:13:06,380 --> 00:13:13,300
OK, so in this example, I'm going to show you as well a live car example with the same code.

160
00:13:13,490 --> 00:13:13,960
All right.

161
00:13:14,750 --> 00:13:21,700
So you can see here the upper part class vehicle, the middle part class private car, and the last

162
00:13:21,710 --> 00:13:28,130
part, which is the instance of an object, then also the running of this metal right here.

163
00:13:29,540 --> 00:13:40,550
So first of all, I said that vehicle keyword is making is giving us the ability to use this instance

164
00:13:40,550 --> 00:13:42,940
of an object from here.

165
00:13:43,170 --> 00:13:47,570
It allows us to use engine status, which belongs to the upper class.

166
00:13:48,510 --> 00:13:49,550
So let's test it.

167
00:13:50,150 --> 00:13:52,520
Let me remove this keyword and see what happens.

168
00:13:53,780 --> 00:13:57,850
You see, once they remove this keyword immediately, you can see it back around here.

169
00:13:58,130 --> 00:14:05,330
And once they hover above it, it says unresolved attribute reference engine status for class, private

170
00:14:05,330 --> 00:14:05,640
car.

171
00:14:06,740 --> 00:14:12,100
It basically says to me, hey, do you have an instance of private car?

172
00:14:12,380 --> 00:14:17,120
Why the hell are you using a method that belongs to a different class?

173
00:14:17,420 --> 00:14:19,070
I'm not familiar with it.

174
00:14:19,370 --> 00:14:20,210
With that method.

175
00:14:20,390 --> 00:14:21,490
Not familiar with it.

176
00:14:21,740 --> 00:14:22,310
What is it?

177
00:14:22,310 --> 00:14:23,660
What is engine status?

178
00:14:23,840 --> 00:14:25,520
It's not part of private car.

179
00:14:26,620 --> 00:14:31,510
All right, but once I bring back the vehicle.

180
00:14:32,610 --> 00:14:33,120
OK.

181
00:14:34,140 --> 00:14:37,220
Once I bring back the vehicle into the wrong brackets, everything's fine.

182
00:14:39,100 --> 00:14:41,840
All right, so this is regarding the method.

183
00:14:42,160 --> 00:14:44,650
Now let's talk about the Parmeter, OK?

184
00:14:46,580 --> 00:14:51,080
You can see the super here, the freeze now let me try to remove it.

185
00:14:51,290 --> 00:14:52,960
OK, let's say we don't need it.

186
00:14:53,120 --> 00:14:56,230
And once we initiated this method, everything's fine.

187
00:14:56,240 --> 00:15:02,670
The true variable goes from here and goes automatically to the top into here, right into your status.

188
00:15:03,020 --> 00:15:04,700
Let me just try to remove this in it.

189
00:15:06,510 --> 00:15:12,270
And immediately you can see brownish background on the inside of the child here once hovering above

190
00:15:12,270 --> 00:15:12,510
it.

191
00:15:13,470 --> 00:15:14,540
Let's see what it says.

192
00:15:15,210 --> 00:15:16,950
Call to end it off.

193
00:15:16,950 --> 00:15:18,910
Superclass is missed, OK?

194
00:15:19,050 --> 00:15:20,010
He's telling me.

195
00:15:23,950 --> 00:15:28,510
He's telling me you're trying to get inheritance here, OK?

196
00:15:28,750 --> 00:15:34,600
You're trying to get inheritance here, but what about the super phrase, OK, I can't use inheritance

197
00:15:34,600 --> 00:15:35,700
without the super phrase.

198
00:15:37,030 --> 00:15:39,790
And once we have over here, everything's fine.

199
00:15:40,210 --> 00:15:46,600
OK, so this variable goes from here to here than to here and here.

200
00:15:46,780 --> 00:15:52,480
And then from this line, it goes up to here and then here.

201
00:15:53,080 --> 00:15:53,470
Right.

202
00:15:54,370 --> 00:15:56,980
And then when I run engine status.

203
00:15:58,050 --> 00:16:07,440
OK, this method I'm going to use is true, right, so it's already past up to here, so it's OK, it's

204
00:16:07,440 --> 00:16:08,490
going to get the value.

205
00:16:09,780 --> 00:16:10,800
Let's try to run it.

206
00:16:12,060 --> 00:16:13,920
OK, so I'll have it through here then.

207
00:16:13,970 --> 00:16:15,810
Engine is running then.

208
00:16:15,810 --> 00:16:22,050
If I put false here, I'm going to get engineers off.

209
00:16:22,800 --> 00:16:23,120
Right.

210
00:16:24,240 --> 00:16:27,600
And then once I'm going to put A, B, C here.

211
00:16:29,420 --> 00:16:31,930
So wrong value inserted.

212
00:16:32,160 --> 00:16:34,200
It's going to replace the deflection point.

213
00:16:34,760 --> 00:16:38,270
I think this covers perfectly the inheritance topic.

214
00:16:38,630 --> 00:16:43,490
You can always you can also find this block of code attached to the lecture.

215
00:16:43,640 --> 00:16:49,280
And I'm highly recommend you to copy it into a pie chart and to do some experiments, because my best

216
00:16:49,280 --> 00:16:54,770
learning experience was by making making experiments on other people's code.

217
00:16:55,370 --> 00:16:57,770
Thank you for listening and I will see you the next video.