"""
Ex 9.1 in "A primer on..."
Demonstrate inheritance by creating an "empty" 
subclass, and use the builtin function dir and
the __dict__ attribute to inspect its contents. 
"""
import numpy as np

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

class Parabola0(Line):
    pass

p = Parabola0(1,1)

#The builtin function dir lists all the contents of an object:
print("All contents of Parabola instance 'p':")
print(dir(p))

"""The attribute __dict__ is automatically created by Python, and
is a dictionary containing the defined attributes of an instance."""
print("Attributes of Parabola instance 'p':")
print(p.__dict__)

"""
Terminal> python dir_subclass.py 
All contents of Parabola instance 'p':
['__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']
Attributes of Parabola instance 'p':
{'c0': 1, 'c1': 1}
"""