如何使用装饰器将 function 的结果包装在多个外部库函数中

Question

I've only recently learned about decorators, and despite reading nearly every search result I can find about this question, I cannot figure this out. All I want to do is define some function "calc(x,y)", and wrap its result with a series of external functions, without changing anything inside of my function, nor its calls in the script, such as:

@tan
@sqrt
def calc(x,y):
    return (x+y)

### calc(x,y) = tan(sqrt(calc(x,y))
### Goal is to have every call of calc in the script automatically nest like that. 

After reading about decorators for almost 10 hours yesterday, I got the strong impression this is what they were used for. I do understand that there are various ways to modify how the functions are passed to one another, but I can't find any obvious guide on how to achieve this. I read that maybe functools wraps can be used for this purpose, but I cannot figure that out either.

Most of the desire here is to be able to quickly and easily test how different functions modify the results of others, without having to tediously wrap functions between parenthesis... That is, to avoid having to mess with parenthesis at all, having my modifier test functions defined on their own lines.

Answer 1

A decorator is simply a function that takes a function and returns another function.

def tan(f):
    import math
    def g(x,y):
        return math.tan(f(x,y))
    return g