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Slowing Down Code With Decorators

Decorators can be used to slow code down. Slowing down code can be useful when working with web services or when you want to rate limit a function. In this lesson, you’ll see how to create a @slow_down decorator that sleeps one second before it calls the decorated function.

00:00 Now that you’ve done the debugging, what if you need to slow a function down? How could this be useful? You could be troubleshooting an API, accessing information over a network, or maybe you simply need to put a function into a wait state.

00:14 So you could have a handy, ready-made decorator to use in these circumstances. Back in the decorators module, go ahead and copy the boilerplate decorator.

00:29 Place it below your last one, debug().

00:35 Just as a note, if you’ve skipped around, this decorator will require the import of time also, so make sure that’s still there. This new decorator will be named slow_down().

00:47 It will receive a function. It will """Sleep 1 second before calling the function"""put that in your docstring. Rename the wrapper—wrapper_slow_down().

01:00 Using time, that you’ve imported from the standard library, use the sleep() method and enter into it 1 second.

01:14 And this time, simply return the function that you’re wrapping here with its *args and **kwargs. Lastly, return wrapper_slow_down.

01:24 That’s it! Save. Switch back to examples.py. Again, this one is importing all of the decorators. In the examples module, use your new @slow_down decorator and make a simple countdown().

01:47 It’ll accept as an argument a from_number.

01:57 So here, it’s going to do a little bit of recursive functionality…

02:05 calling itself, again, using the current from_number - 1. So again, you’re defining countdown(), starting with an integer as a from_number.

02:18 If the from_number is less than 1, it’ll print "Liftoff!". else: it’ll print the current from_number and then run countdown()—or call countdown(), again, with from_number - 1.

02:31 And remember, each of those calls is decorated by @slow_down. Let’s save. So as you can see here, your decorator is showing the docstring, which is nice.

02:43 It’s going to Sleep 1 second before calling the function each time. Okay. Save, enter into your REPL, and from examples import countdown. Great, that worked fine. Inspect countdownit’s a function. That all looks great. All right. To run it, enter in countdown() and put an argument of a number of seconds—in this case, 3.

03:15 That worked perfect. So, controlling the rate that functions get called could be very useful if you’re accessing services from the internet, like troubleshooting an API. Next, let’s talk about registering plugins.

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