Useful python – Class based decorators and context managers

There are many things why Pyhton is my standard go-to language if it comes to implement something. It’s either a website, automation, data-mining or complex calculation Python excels in most of it. I decided to write some of my favourite things which just makes things cleaner and easier to implement.

1. Class based decorators and context managers

I’ve already wrote a post where I mentioned the power of decorators. Now I want to take it to a step further. In spite of the most example can be found online decorators can be written as classes simply because everything in Python is an object. You just need to specify the __call__ method as you would do it with your function.

However sometimes you already have one (or more) decorator around your functions and it’s not really good to overdecorate your functions. Also you might not want to create a separate function because only small part of your method needs to be wrapped with the decorator’s behaviour. For example timeout. This is where context managers come into play.

Just like for examples Django’s transaction contexts your decorators can be written in a way that it can be used as a with context as well.

Here is a simple example:

In both cases we’re going to get timeout.TimeoutException.

So how to implement this? The only trick is you need the __enter__ and __exit__ for the context manager behaviour and __call__ for the decorator. Here’s a simple example:

 

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About charlesnagy

I'm out of many things mostly automation expert, database specialist, system engineer and software architect with passion towards data, searching it, analyze it, learn from it. I learn by experimenting and this blog is a result of these experiments and some other random thought I have time to time.
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