#100DaysOfCode in Python Transcripts
Chapter: Days 22-24: Decorators
Lecture: Quick primer on decorators
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All right, a quick primer on decorators.
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What is a decorator?
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I think the best way to explain it
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is that a decorator can add behavior to a function,
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so you pass the function into a decorator,
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it can do something before and or after
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and returns the newly decorated object.
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And it's just one of those common design patterns
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as described in design patterns
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the elements of reusable object oriented software.
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So let's import the modules we're going to use.
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And let's define our first decorator.
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Just a very basic one to show the syntax.
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Alright, now you can use the mydecorator
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to decoratate a function, and this is the syntax for that.
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I will go into some of the details in a bit before,
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example, why should you use wraps which is not required.
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And the whole aspect of args and keyword args.
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For now, at the very basic level, just remember,
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a decorator takes you function, needs an inner function
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to pass in the arguments and keyword arguments
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and calls the function and see this sandwich effect here,
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so you can do something before calling the function
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and after it, so for example,
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when you write a decorator to time your function,
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here you would start the timing,
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here you would call the function,
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and here you would stop the timing.
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You can look at it as adding behavior before
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and after the function.
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The function gets called, but additional logic
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is added around it and that's what a decorator is for.
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And then here is the syntax how to use it.
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So right before the function you
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use the at sign, @decorator.
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If you have been using any web framework
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like Flask for Django, you're familiar with this syntax.
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As we will see towards the end,
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there is a login required decorator for example in Django
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that uses this concept of adding a behavior
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which is that case is to see if the user is logged in
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and it adds that behavior to a function
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which is that case is usually the logic of a web page.
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A route to a certain web page.
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And keep in mind that this is just syntax,
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the same thing could be written as...
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So here you see actually that myfunction
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gets passed into the decorator,
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but this is the common way
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how you would use a decorator.
