This error looks scary, but it’s actually a helpful message from a developer. In Python, the NotImplementedError is not a bug; it’s a feature of Object-Oriented Programming (OOP).
It means: “You are supposed to write this method yourself, but you forgot.”
The Cause: Abstract Methods
Programmers create “abstract” parent classes (blueprints) that are meant to be inherited from. They use NotImplementedError to force the child classes to create their own versions of a method.
Example: The Parent Class (The “Blueprint”)
class Shape:
def draw(self):
# I am a blueprint. I don't know how to draw!
# I force my children to define this.
raise NotImplementedError("You must implement the 'draw' method!")The Problem Code (The “Child” Class): You inherit from Shape but forget to define your own .draw() method.
class Circle(Shape):
def get_radius(self):
return 10
# Whoops, we forgot to add a 'draw' method!
my_circle = Circle()
my_circle.draw() # CRASH! NotImplementedErrorThe Fix: Implement the Method
You must “override” the parent’s placeholder method with your own real code.
Correct Code:
class Circle(Shape):
def get_radius(self):
return 10
# HERE IS THE FIX:
def draw(self):
print("Drawing a circle...")
my_circle = Circle()
my_circle.draw() # Output: Drawing a circle...If you see this error, Python is telling you that you need to go into your class and write the function that the parent class (or library) is demanding.
