#100DaysOfCode in Python Transcripts
Chapter: Days 22-24: Decorators
Lecture: Concepts: what did we learn
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Alright now it's time to review what we've learned,
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how to write a decorator.
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A decorator takes a function to be decorated.
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It adds behavior before, and or, after.
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Then it returns the function.
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Don't forget to use wraps to the preserve the doc string.
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Args and keyword args.
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There are various ways you can call a function in Python.
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The simplest way is to use a required, positional argument.
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If I leave off this argument, I get an error.
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The second type, is the keyword argument
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which can be set to a default.
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And then we have two arbitrary sequences which are the list,
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in this case sports, and keyword arguments
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which always go last.
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Here is an example how you would call this
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with all the types of arguments.
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Let's write a timeit decorator.
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It takes a function, starts the timer
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before calling the functions, calls the function,
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and ends the timer,
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printing how long the function took to execute.
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We define the decorator.
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Here's how to apply it to a function.
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You can stack decorators.
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Note that the order matters.
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As timeit is the outer decorator,
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that's the one that wraps at the outer level.
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Some examples of common decorators.
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Here are two from the Flask documentation.
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One checks if a user's logged in
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and the other is performing caching.
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Those are ideal examples of decorators
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because they abstract away common behavior
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which you want to apply to multiple functions.
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Here's another example of a well known decorator
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called LRU Cache.
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You can find those in the Flask
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and the Python documentation respectively.
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And now it's your turn.
