Well, what python calls a "decorator" is just a function that accepts a function and returns a function with roughly similar functionality. In python, the old way to decorate functions was

    def my_decorator(f): ...
    def my_function(...): ...
    my_function = my_decorator(my_function)

and the new "@my_decorator" syntax is just sugar for this.

Function composition is only one of many things you can do with decorators. You could implement a K-combinator with them if you wanted to:

    def kestrel(x):
        "decorates a function to evaluate that function, but then return x"
        def decorator(f):
            def g(*args, **kwargs):
                f(*args, **kwargs)
                return x
            return g
        return decorator

    @kestrel(4)
    def foo(x):
        y = x + 1
        print y
        return y

    foo(5) # => 4, but prints 6