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Decorators are special functions that return other functions and they are used

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to modify the way that a function works.

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There's a special syntax for using decorators in Python.

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Let's take a look at how that works.

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Let's make a working copy of decorators.py and we will call it

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decorators-working.py and we will open that up, and we will see we have

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our Duck example here.

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This one has a properties variable that's getting set by the keyword arguments,

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and it has a way of setting properties and getting properties.

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Down here we have set a property in our constructor and we were getting that

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property in this print function.

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So if we run this, we see that we are printing out that color.

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Now, one of the most common uses for decorators in Python is to create accessor

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methods for variables.

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For examples, if I wanted special accessors for color, I can define a function

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called color and configure it like a getter.

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So I'll return self.properties.get ('color') and with a default value of None.

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What turns this into an accessor is this decorator function that looks like that.

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With an @ sign and the word property, and that turns this into an accessor for

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the variable called color.

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Then I can create a setter by saying @color.setter and def and I name it exactly

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the same thing, color.

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This is all special syntax that's designed just for this purpose. I set an argument.

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We will call it c and we will set self.properties sub 'color' = c, and now we have our setter.

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Finally, color.deLeter, sub 'color' again, and delete self.properties sub 'color' and what

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this allows us to do is this.

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I can see donald.clolor = 'blue'.

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I don't need to initialize it here any more.

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So if I save that and run it, we will see that it still works the way that we want it to.

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Here I can just say donald.color.

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Now, this might look like I went to a lot of trouble to just be able to use a

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property that I could have just used without all of this trouble and it would

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have set the property in the object, and read the property from the object.

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But the beauty here is that now it's under the control of the object. And so if

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I wanted to do some thing else in here when I set this.

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If I wanted to save it to a database or if I wanted to create a database based

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on a filename, which is an example of how I have used this recently.

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Then in the deLeter, if I wanted to close the database based on that filename.

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So now I can do all of those things, but I still have this convenient syntax.

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So this is the most common use of decorators and this is a little bit of the

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power of decorators as well, is it they can fundamentally change the behavior of

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a function, because here I have got function methods which are operating a

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setters and getters, but I am not calling them as functions. I am calling them

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in this simple normal properties syntax.

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So that's the power of decorators and that's a simple example of how you can use

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decorators in your objects.