How to warn about class (name) deprecation

Maybe I could make OldClsName a function which emits a warning (to logs) and constructs the NewClsName object from its parameters (using *args and **kvargs) but it doesn't seem elegant enough (or maybe it is?).

Yup, I think that's pretty standard practice:

def OldClsName(*args, **kwargs):    from warnings import warn    warn("get with the program!")    return NewClsName(*args, **kwargs)

The only tricky thing is if you have things that subclass from OldClsName - then we have to get clever. If you just need to keep access to class methods, this should do it:

class DeprecationHelper(object):    def __init__(self, new_target):        self.new_target = new_target    def _warn(self):        from warnings import warn        warn("Get with the program!")    def __call__(self, *args, **kwargs):        self._warn()        return self.new_target(*args, **kwargs)    def __getattr__(self, attr):        self._warn()        return getattr(self.new_target, attr)OldClsName = DeprecationHelper(NewClsName)

I haven't tested it, but that should give you the idea - __call__ will handle the normal-instantation route, __getattr__ will capture accesses to the class methods & still generate the warning, without messing with your class heirarchy.

Please have a look at warnings.warn.

As you'll see, the example in the documentation is a deprecation warning:

def deprecation(message):    warnings.warn(message, DeprecationWarning, stacklevel=2)

In python >= 3.6 you can easily handle warning on subclassing:

class OldClassName(NewClassName):    def __init_subclass__(self):        warn("Class has been renamed NewClassName", DeprecationWarning, 2)

Overloading __new__ should allow you to warn when the old class constructor is called directly, but I haven't tested that since I don't need it right now.