"""
Ex. 9.1 from "A primer on..."
Demonstrate the "magic" of inheritance
by creating a dummy subclass that adds nothing
to the base class, and inspect its 
contents using the dir-function. 
"""


import numpy as np

class Line:
    def __init__(self, c0, c1):
        self.c0 = c0
        self.c1 = c1

    def __call__(self, x):
        return self.c0 + self.c1*x
    
    def table(self, L, R, n):
        """Return a table with n points for L <= x <= R."""
        s = ''  
        for x in np.linspace(L, R, n):
            y = self(x)
            s += f'{x:12g} {y:12g}\n' 
        return s
    
#dummy class, inherits everything from Line, but adds nothing:
class Parabola0(Line):
    pass

#create an instance and check its attributes:
p1 = Parabola0(1, 1)
print(dir(p1))
print(p1.__dict__)


"""
Terminal> python dir_subclass.py 
['__call__', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'c0', 'c1', 'table']
{'c0': 1, 'c1': 1}
"""