A class field as a function pointer in Python

Question

I want to have a function pointer in my class Point.

class Point:
  coord=[]

  def value(self,p_coord:list=coord):
    return abs(self.val(p_coord))

  def __init__(self,p_coord:list,p_val):
    self.coord=p_coord
    self.val=p_val

I'm trying to pass a function pointer to the field "val", But when I try to call the function with the method value(), it returns 0:

def length(par:list):
  return len(par)

v1=Point([1, 2, 3],length)
print(v1.value())

How to pass a function to a class field?

Answer 1

The default value coord in value is the class attribute from line 2 which is not the same as the instance attribute self.coord set in __init__. So the function pointer is working correctly, its just looking at the wrong list.

What you can instead do is:

def value(self, p_coord=None):
    if not p_coord:
        p_coord = self.coord
    return abs(self.val(p_coord))