All functions are also descriptors, so you can bind them by calling their __get__
method:
bound_handler = handler.__get__(self, MyWidget)
Here’s R. Hettinger’s excellent guide to descriptors.
As a self-contained example pulled from Keith’s comment:
def bind(instance, func, as_name=None):
"""
Bind the function *func* to *instance*, with either provided name *as_name*
or the existing name of *func*. The provided *func* should accept the
instance as the first argument, i.e. "self".
"""
if as_name is None:
as_name = func.__name__
bound_method = func.__get__(instance, instance.__class__)
setattr(instance, as_name, bound_method)
return bound_method
class Thing:
def __init__(self, val):
self.val = val
something = Thing(21)
def double(self):
return 2 * self.val
bind(something, double)
something.double() # returns 42