I’m trying to create a decorator that is called within a class, which would pull attributes from that class, and use those class attributes to edit the function’s docstring.
My problem is that I have found examples of decorators that edit the docstring of the function (setting the function's __doc__ attribute equal to a new string), and I have also found examples of decorators that pull attributes from the parent class (by passing self into the decorator), but I haven’t been able to find an example of a decorator that is able to do both.
I have tried to combine these two examples, but it isn't working:
def my_decorator(func):
def wrapper(self, *args, **kwargs):
name = func.__name__ # pull function name
cls = self.__class__.__name__ # pull class name
func.__doc__ = "{} is new for the function {} in class {}".format(
str(func.__doc__), name, cls) # set them to docstring
return func(self, *args, **kwargs)
return wrapper
class Test():
@my_decorator
def example(self, examplearg=1):
"""Docstring"""
pass
With this, I would hope that the following would return "Docstring is now new for the function: example":
Test().example.__doc__
Instead it returns None.
Edit: Note that I am not interested in how to access the name of the class specifically, so much as how to access the class attributes in general (where here self.__class__.__name__ is used as an example).
Turns out that accessing class attributes from within a class is impossible, as the class has yet to be executed when the decorator is called. So the original goal - using a decorator within a class to access class attributes - does not seem to be possible.
However, thanks to jdehesa for pointing me to a workaround that allows access to the class attributes using a class decorator, here: Can a Python decorator of an instance method access the class?.
I was able to use the class decorator to alter the specific method's docstring using class attributes like so:
def class_decorator(cls):
for name, method in cls.__dict__.items():
if name == 'example':
# do something with the method
method.__doc__ = "{} is new for function {} in class {}".format(method.__doc__, name, cls.__name__)
# Note that other class attributes such as cls.__base__
# can also be accessed in this way
return cls
@class_decorator
class Test():
def example(self, examplearg=1):
"""Docstring"""
print(Test().example.__doc__)
# Returns "Docstring is new for function example in class Test"