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Object oriented programming is a code in paradigm which relies on classes and objects, and classes

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are simply viable types, weight attributes and properties.

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Those attributes of a class are variables and the properties are methods in the section which are look

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at classes and objects, operator overloading method times, inheritance, encapsulation and polymorphic.

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Suppose we want to design a program which produces smileys based on some inputs we could define as smiley

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framework like this one.

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And the way we define such a framework is by defining the class so we can have a class smiley with attributes

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like a smile.

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So let's do this.

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We have an attribute like is smile.

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Which is said to true.

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We have an attribute like face colour, face colour which is set to white, an attribute like eye colour

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which is set to white.

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There's actually a string.

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So we set up to whites.

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Whites.

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And then this class could have several properties or methods like, for example, the set smile method.

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So since the method we have the deaf set smile.

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We turn for now none.

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We could define the set face color we turn on.

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We have the set eye color.

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We turn it on and there we go.

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We have our smiling class.

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So there we go.

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We have this smiley class, which we've defined.

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But actually, this class is just a framework.

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And to put it alive, we need to make use of an object, which is an instance of this framework or some

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sort of version of this framework.

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It's coming back to the slide.

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As you can see, we have this from here.

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We could create an object or an instance of this frame with these color orange, eye color blue, and

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then is smile.

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That is the smile is true.

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Since I could see her smiling, we could also create an object instance where in the face is light blue.

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The eye color is red.

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And then we also have this other object instance.

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Well, if smile is false, I call a white and then face color black.

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So from this example, we see how based on this frame, we are able to generate different smileys and

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the different versions or instances of this frame or class is what we call the object.

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So now let's see how we create a simple object.

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We could say smiley, let's say happy with that.

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We have this smiley and then we do a happy.

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That is smile.

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For one, that we have an area, obviously, because this is smile isn't a function but just an attribute.

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So take this off or on that we see.

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We have happy smile.

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Now let's create another object.

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We have the objects that smiley you see sad.

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That is smile.

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Wrong again.

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We'll see.

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Is still true.

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Now one to make Buddhists modify this object size that we have, this is smile to be false.

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Now to do this, we could now make use of the set smile functions.

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So let's go ahead and modify this.

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We're taking the smile or let's say current smile or this is smile status, smile status.

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And then we return.

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Still known, but what a difference that what we're doing is was set in is smile to be false.

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All right is smile is this smile steady is not actually false.

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So this smile the smile stage is a one of change.

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This attribute of the class to become now while we put in here so set smile now gets in your all set

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smile takes in the smile attitude and then modifies it is smile.

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And then from this now which I'll see while we get after passenger to set smile function so around this

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obviously is true but once the defined is which is that set smile and then we see false wrong again

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and we see that we have an error.

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Now this error reads that the set smile takes one positional argument but somewhere given.

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Okay, before looking at this, let's do some recap.

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We have defined this object that is, we have defined version of the smiley class, which is sad.

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Previously we had defined as other version happy of those smiley class.

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And then yeah, we're like Colleen on this set smile function, which is other set smile method, which

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is part of the smiley class.

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So what we do is we have set that set smile and then we pass in the smile status, which is false obviously

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if was sad and the smile status to be false so is smiley should be false.

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Now, once it has this, we are now ready to call again on its smile to be sure that is actually false.

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But then we have in this error.

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Now having this error is very normal and we shall see how to solve this problem or how to correct this.

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The way we correct this error is by giving each object some sort of identity in this class.

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So what we're going to do now is instead of just defining the methods in the class as if all the objects

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behaved the same, we are going to give it an identity.

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So we have would define the self right here and then.

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Now we have self, self and for this year we have self, self, self.

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This is actually a key word using Python and other programming languages like Java.

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You have this now coming back to this where we define our attributes and then we've added one extra

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argument in all our functions.

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Now the reason why we're doing this is because we want to give this class or right to give each object

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created based on this class an identity which is going to be different from this other one right here.

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So this means that whenever we create this or if we create an object they happy from this class is going

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to have a different identity from this other one.

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By identity will mean is going to have a different way of working with this functions or methods.

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And also the attributes are going to be different.

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And this is done simply by using this self.

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Now, that said, let's run this.

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We see that we have an error.

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We thought that a solve is not defined.

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Now, the way we solve this is by including a constructor.

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So instead of having to put this attribute all the way we've just done, we are going to define a constructor.

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And the constructor is just a special type of matter.

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So we have this in its method.

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This init method is what we call the constructor.

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Not that you cannot see.

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For example, you cannot do this.

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You can just define in there like this and then expect it to work.

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So this indeed has to have to double on the cars before and then two on this class after.

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So double before and then double after.

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Once we have this, now it's in this constructor that would define those attributes for the class or

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actually this object attributes.

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So now let's run again.

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You see that everything works fine now.

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And that's simply because this attribute, all right.

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Of this class has been defined such that we could now, for every object, define its own attributes.

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There's an error here.

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We shall skip this.

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Like we should just run this for now.

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So let's run again.

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We see that we have this error and take note.

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We must also have the self that's passing in.

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Neat.

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So let's run again.

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And there we go.

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It works fine now.

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So obviously this is Smile belonged to the class smiley but now this is smile is actually the is smile

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for this happy object.

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And the way we did this was by using the South and then by including a constructor.

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So on that.

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That's fine.

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Now, let's come back to this or this.

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And there we go.

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We see that this time around, the code works fine.

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But we are having a true instead of a false.

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So what do we do to solve this problem?

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The simple way we could solve this problem is by instead of saying is smile as if this is smile belonged

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to the class.

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We have self that is smile.

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So that Python knows that this is smile is actually the attribute for this set object.

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So let's run again.

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And there we go.

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Everything works fine.

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Now we have this as false.

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So sad.

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That is smile is false and happy.

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That is smile.

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It's true.

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We could go ahead and modify this again.

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Let's suppose we want to do this in a way that undefined in the smile we just see.

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For example, we see the past and the status quo is smile status, is smile status.

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And then instead of having this status of run this, we have an arrow.

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Because normally the way the construct has been defined, we have all we are meant to pass in any value

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right here.

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So what we do is we're going to have this yeah, we'll see this smile.

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So by default, we will set it to true.

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By default is true.

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So now.

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Yeah, we have the smile.

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Okay, let's run this again.

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And there we go.

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We set out without having to explicitly call on the set smile method.

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We already have the set turn to false.

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All the is smile for set then to false.

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Let's take this off.

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So you see that it works.

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So that's it.

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So we see that setter is smiles false because of the way it was defined.

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And that was the role of this init function, which is actually a constructor.

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So we are constructing this object based on this class.

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By already defining a smile in such a way that it is true.

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And the case where we have, for example, just happy by default years since we don't pass anything

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by default, it's true.

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And then when we want it to be false, we have just to specify that I want it to be false.

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Now the next step will be to take this and say, okay, this color will repeat for the first color we

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set it to default whites.

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We do the same for the I color.

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We set it to default.

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Whites That's it.

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So that we then we go, we have the face color.

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Yeah, we have the face color around this.

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Everything was fine.

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Let's now set this face color to see orange.

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Orange.

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And then we have said, now let's put it in black.

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We have a black.

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The slight that's a black said the face color.

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So on that that we go so we see that now our side is good.

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Most of this of print simply print is.

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Wrong again.

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Okay.

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So now we have four black.

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And then we could also obviously into the eye color.

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Eye color?

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No, I closed white.

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So just take this will let.

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So let's print out now the eye color.

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Sad that I actually saw that eye color on it.

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There we go.

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We have the face.

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Got a black, eye color black.

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And then this is smiles false.

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So this isn't as the smile and smiley.