Constructing Leaf
Input
get_init_order()
Output
['Base', 'Mid', 'Leaf']
Leaf.__init__ should call super().__init__ which in turn will call Base.__init__ through Mid, producing the ordered list.
Full lesson preview
Use super() Across a Multi-Level Inheritance Chain
Practice using super() to ensure cooperative initialization across multiple inheritance levels.
Python practice15 minInheritance & PolymorphismIntermediateLast updated April 8, 2026
Problem statement
You are given a three-level inheritance chain: Base <- Mid <- Leaf. Each class should record its initialization by appending a label to an instance list attribute in the correct order (Base first, then Mid, then Leaf). Implement Mid.__init__ and Leaf.__init__ so that they cooperate with Base using super(). After construction, the Leaf instance's order attribute should be ['Base', 'Mid', 'Leaf'].
Implementations that fail to call the parent initializer (or call it incorrectly) may produce the wrong order or cause errors. Use super() to call the parent initializer.
Task
Implement constructors that use super() so that each class in a chain contributes to instance initialization in order.
Examples
Input format
Single expression calling a function or constructing a class, e.g., get_init_order() or Leaf().order
Output format
A list showing initialization order, e.g. ['Base', 'Mid', 'Leaf']
Constraints
Do not modify Base.__init__. Implement Mid.__init__ and Leaf.__init__ using super(). No external libraries.
Samples
Sample 1
Input
Mid().order
Output
['Base', 'Mid']
Mid must call Base's initializer so instances of Mid have both 'Base' and 'Mid' in order.