ICPO
ICPO is a mnemonic for Python attribute lookup order across an instance, its class, parent classes, and the object hierarchy.
Python Workout: 50 ten-minute exercises
A name-resolution order for locating attributes across an instance, its class, parent classes, and the object hierarchy.
- How it is used
- Guides reasoning about Python attribute access, methods, class attributes, inheritance, and subclass-specific behavior.
- How deep it goes
- Traces lookup from instance through class and parents to object, then applies it to shadowing, inheritance, and super without runtime internals.
- Examples
- Uses str.upper, Foo and Bar methods, Bowl.max_scoops, BigBowl overrides, and Employee calling Person.__init__.
- What you can do after
- Diagnose/debug attribute results, predict inherited method calls, avoid accidental shadowing, and reuse methods across subclasses.
Read how Python Workout: 50 ten-minute exercises explains ICPO →
Python Workout, Second Edition
ICPO is a mnemonic for Python attribute lookup order: instance, class, parents, and object.
- How it is used
- Explains Python attribute access, method retrieval, inheritance, class attributes, and instance shadowing.
- How deep it goes
- Works through lookup order, inheritance, shadowing, super, and subclass-specific class attributes without descending into descriptor internals.
- Examples
- Uses string methods, Person and Employee, and Bowl and BigBowl class attributes to demonstrate lookup and reuse.
- What you can do after
- Diagnose attribute-resolution surprises and design inherited methods that honor instance- or subclass-specific values.
Related concepts
- LEGBcontrasts with · LEGB is Python’s name-resolution order of local, enclosing-function, global, and built-in scopes.
- attribute lookupimplements · Attribute lookup is Python's runtime process for resolving a named attribute through an object's instance, class, inheritance hierarchy, and base objects.
- static fieldused by · A static field is a named variable whose storage is associated with a class or program scope rather than separately with each object instance.
- attributeconfigures · An attribute is a named property, value, or piece of information associated with an entity, object, or program element.
- inheritanceused by · Inheritance is a mechanism by which a child type or element receives properties, values, or behavior from a parent, subject to system rules and possible overrides.
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