Accessing signatures of overriding methods in subclasses

Question

In python3.8.5, I am working with an existing class superClthat defines a method f, and multiple existing subclasses sub1, sub2... that override f with different numbers of variables. Based on How to create new subclasses by adding the same method to multiple classes, I would like to add a new function gto all subclasses via the superclass. The new function should call fand do things with it. The problem is that each subclass has a different signature for f. How can I get around that? Sample code follows:

import numpy as np

class superCl(object): # Exists already
    def f(self, x): return x

class sub1(superCl): # Exists already
    def f(self, x, a, b): return x / (b - a)
        
class sub2(superCl): # Exists already
    def f(self, x, tau): return 1/tau * np.exp(-x/tau)
        
sc = superCl()
print(sc.f(0))

s1 = sub1()
print(s1.f(0, 1, 2))

s2 = sub2()
print(s2.f(0, 1))

def g(self, x1, x2, ...): # New, calls existing method.  Is there some way to get the signatures and values from the subclasses, eg self.args?
    print('Extra meth')
    self.f(x1, ...) - self.f(x2, ...) # How to adapt to proper arguments for f for each sublcass?

superCl.g = g # New method gets added to new and existing instances

print(sc.g(0, 1))
print(s1.g(0, 1, 1, 2))
print(s2.g(0, 1, 1))

EDIT: Superclass defines a generic set of functions; subclasses are particular cases, each with different variables. Function freturns value of function for subclasses parameters; function g I am trying to create evaluates the difference in f at two different points.

It’s difficult to suggest an answer without knowing what the parameters mean. For instance, you have ‘s2.f(2,3)’, so, if you call ‘s2.g()’, what parameters would you expect the subsequent call to ‘s2.f(...)’ have? — quamrana, Jul 17 '21 at 09:41
@quamrana Thanks for comment. Have edited question. ```f```is a function that depends on a variable ```x``` and on a subclass-dependent number of parameters. Is there some way to access these with ```args```or something similar? — Mister Mak, Jul 17 '21 at 11:11

score 0 · Accepted Answer · answered Jul 17 '21 at 21:25

Looks like using *args or **kwdsdoes it (Positional argument v.s. keyword argument):

import numpy as np

class superCl(object): # Exists already
    def f(self, x): return x

class sub1(superCl): # Exists already
    def f(self, x, a, b): return x / (b - a)
        
class sub2(superCl): # Exists already
    def f(self, x, tau): return 1/tau * np.exp(-x/tau)
        
sc = superCl()
print(sc.f(0))

s1 = sub1()
print(s1.f(0, 1, 2))

s2 = sub2()
print(s2.f(0, 1))

print('===========================================')
def g(self, x1, x2, *args): 
    print("args", *args)
    return self.f(x2, *args) - self.f(x1, *args)
superCl.g = g
print("--------------------\n"); print("sc", sc.f(1), '-', sc.f(0), "=", sc.g(0, 1))
print("--------------------\n"); print("s1", s1.f(1, 0, 4), '-', s1.f(0, 0, 4), "=", s1.g(0, 1, 0, 4))
print("--------------------\n"); print("s2", s2.f(1, 5), '-', s2.f(0, 5), "=", s2.g(0, 1, 5))

print('===========================================')
def h(self, x1, x2, **args): 
    print("args", args)
    return self.f(x2, **args) - self.f(x1, **args)
superCl.h = h
print("--------------------\n"); print("sc", sc.f(1), '-', sc.f(0), "=", sc.h(0, 1))
print("--------------------\n"); print("s1", s1.h(0, 1, a=0, b=4))
print("--------------------\n"); print("s2", s2.h(0, 1, tau=5))

Accessing signatures of overriding methods in subclasses

1 Answers1