Python - Decorators
There are three issues I see with your current code.
First, you're calling the inner
function, rather than returning a reference to it.
Second, your inner
function doesn't take the same arguments as the function you're decorating. In this case, you need to take at least the x
argument explicitly (some inner functions can use *args
and **kwargs
exclusively, but aparently not yours).
Lastly, you're never calling the wrapped function. While this isn't strictly required (it might be useful to swap out a method with a decorator during development), usually you want to call the function at some point during the inner function's code.
So, to wrap the whole thing together, I think you want your code to be something like this:
def wrapper(func):
def inner(x, y):
if issubclass(x, int): # issue 2
return func(x, y) # issue 3
else:
return "invalid values" # consider raising an exception here instead!
return inner # issue 1
Your decorator should look like this:
def wrapper(func):
def inner(x, y): # inner function needs parameters
if issubclass(type(x), int): # maybe you looked for isinstance?
return func(x, y) # call the wrapped function
else:
return 'invalid values'
return inner # return the inner function (don't call it)
Some points to note:
issubclass
expects a class as first argument (you could replace it with a simple try/except TypeError).- the wrapper should return a function, not the result of a called function
- you should actually call the wrapped function in the inner function
- your inner function didn't have parameters
You can find a good explanation of decorators here.