On 11/13/2022 7:27 AM, Axy via Python-list wrote:
On 11/11/2022 16:21, Ian Pilcher wrote:
Is it possible to access the name of a superclass static method, when
defining a subclass attribute, without specifically naming the super-
class?
A instance's __bases__ attribute is a sequence that contains all its
base classes. So:
class A:
@staticmethod
def double(n):
return 2 * n
class B(A):
def parent_method(self, n):
par = self.__class__.__bases__[0] # For single inheritance
return par.double(n)
b = B()
print(b.parent_method(3)) # 6
# or
print(b.__class__.__bases__[0].double(4)) # 8
Contrived example:
class SuperClass(object):
@staticmethod
def foo():
pass
class SubClass(SuperClass):
bar = SuperClass.foo
^^^^^^^^^^
Is there a way to do this without specifically naming 'SuperClass'?
There is, but it's weird. I constructed classes from yaml config so I
did not even know the name of super class but I wanted similar things
for my clabate templates and I implemented superattr() which works for me:
class BasePage:
body = '<p>Hello</p>'
class MySpecificPage(BasePage):
body = superattr() + '<p>World<p/>'
Actually, it's suboptimally elegant code. Artistic code, to be clear, as
if you looked at modern art and thought: WTF? Also, it's specific for
templates only and supports only __add__.
But I think the approach can be extended to a general superclass() if
you log __getattr__ calls and apply them in __get__ method same way.
I realize this reply is not an immediate help and probably won't help,
but there's always a way out.
Axy.
Here's the code:
class superattr:
'''
This is a descriptor that allows extending attributes in a simple and
elegant way:
my_attr = superattr() + some_addition_to_my_attr
'''
def __init__(self):
self.additions = []
def __set_name__(self, owner, name):
print('__set_name__', name)
self.attr_name = name
def __get__(self, obj, objtype=None):
for cls in obj.__class__.__mro__[1:]:
try:
value = getattr(cls, self.attr_name)
except AttributeError:
continue
for a in self.additions:
value = value + a
return value
raise AttributeError(self.attr_name)
def __add__(self, other):
print('__add__:', other)
self.additions.append(other)
return self Full article:
https://declassed.art/en/blog/2022/07/02/a-note-on-multiple-inheritance-in-python
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