Add method to decorator in Python

In this documentation about lru_cache I can see that there's the possibility to call a function on a decorator with the dot notation, for instance I can call:

lru_cache_decorated_func.cache_info()

What I'm trying to achieve is make my own decorator with my custom function to call that works and is called like cache_info().

So how I can add such a function to a decorator?

Solution

A decorator is nothing more (or less) than a callable returning a callable[0] aka

@foo
def bar():
   ...

is exactly the same as:

def bar():
    ...
bar = foo(bar)

There are various options to "smartify" decorators, what lru_cache does is pretty simple:

it wraps the decorated function in a wrapper function
it then sets to attributes on that wrapper function
and it returns the wrapper (swapping the original function for the wrapper)

import functools

def foo(fn):
    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        return fn(*args, **kwargs)
    wrapper.thing = 'yay'
    return wrapper

@foo
def bar(): ...

print(bar.thing)

will print yay.

[0] or even a not-callable, as is the case for @property or @cached_property.