如何制作一个虚拟的无操作 @jit 装饰器？

Question

I want numba to be an optional dependency, so that it's fast if installed or slow if not. So when numba is not installed, I want @njit to be a dummy decorator that does nothing.

If I follow these directions and use:

def njit(func):
    return func

Then when the decorator is called like @njit(cache=True, nogil=True) I get errors about:

TypeError: njit() got an unexpected keyword argument 'cache'

If I try to catch the args and ignore them using

    def njit(func, *args, **kwargs):
        return func

then I get:

missing 1 required positional argument: 'func'

How do I just make a dummy decorator that does nothing and ignores kwargs?

Answer 1

Think of decorators with arguments as decorator factory, they return a decorator. This way

def decorator(func):
    return func

The above is a decorator, now with arguments

def decorator_factory(a,b,c):
    def decorator(func):
        return func
    return decorator

The inner decorator has access to the a,b,c arguments because is a closure. I hope that helps

---

So it can be defined as:

def njit(cache, nogil):
    def decorator(func):
        return func 
    return decorator

Answer 2

If you want to save some time and be able to do the same with all numba decorators, try numbasub . It provides exactly what you are asking for, and you can apply it to any project you want.

Answer 3

Expanding on geckos' answer, we can adapt it to be compatible with @njit as well.

The code for jit can be found in https://github.com/numba/numba/blob/main/numba/core/decorators.py

What we need to do is to make jit act as a factory decorator when used as @jit() and as a simple decorator when used as @jit.

def njit(f=None, *args, **kwargs):
    def decorator(func):
        return func 

    if callable(f):
        return f
    else:
        return decorator

This should work in both cases.