Force child class to override parent's methods : <p>Suppose I have a base class with unimplemented methods as follows:</p>

<pre><code>class Polygon():
    def __init__(self):
        pass

    def perimeter(self):
        pass

    def area(self):
        pass
</code></pre>

<p>Now, let's say one of my colleagues uses the Polygon class to create a subclass as follows:</p>

<pre><code>import math

class Circle(Polygon):
    def __init__(self, radius):
        self.radius = radius

    def perimeter(self):
        return 2 * math.pi * self.radius
</code></pre>

<p>(H/Sh)e has forgotten to implement the area() method.</p>

<p>How can I force the subclass to implement the parent's area() method?</p>
