This exception is used during development to indicate that in that place you need to implement some functionality. As always, to learn how to fix any kind of exceptions we start with checking exceptions on or StackOverflow.

However this time I want to give a detailed explanation on certain exceptions.

For example method in a subclass.

Let's define a parent class:

class Animal(object):
def __init__(self, speed):
self.speed = speed
def run(self):
raise NotImplementedError('You need to implement this method in %s.' % self.__class__.__name__)

And some child classes which will inherit all methods:

class Rabbit(Animal):

Now let's try to create a class instance and run a method from the parent class:

rabbit = Rabbit(speed=20)


in run raise NotImplementedError(NotImplementedError: You need to implement this method in Rabbit.)

So it says that you are using a method that actually is not implemented, so most likely you have to implement it in Rabbit class.

Screaming women after seen Not Implemented error