Nested decorator functions in Python

When I was at PyConIE last October I was talking with an old friend about Python’s decorator functions.

He lamented how you need to google around for tutorials any time you wanted to write a parametrised decorator because it can be so confusing. I told him that there was a way to do it by nesting decorator functions which is much simpler than implementing them using classes (which seems to be the widely known about way).

I thought I’d write up this quick blog post with some examples that will demonstrate how to do this and serve as a reference in case I forget any of this stuff myself!

Using classes

So here’s a rick rolling example using classes:

Using nested functions

And here’s the corresponding example which uses nested functions:


In summary: class decorators are confusing because arguments and functions are sent to different places depending on the context. Nested function decorators are a neater abstraction because the base decorator is the same in both cases, if you want parameters you just wrap it in an additional function.

Hope this comes in handy!

Nested decorator functions in Python