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What is __init_subclass__ in Python?

Q: What is __init_subclass__ in Python?

**`__init_subclass__`** is an implicit **classmethod** on a base class that Python calls **every time a subclass is defined** (not when instances are created). It's a lightweight hook for **validating or registering** subclasses — most of what people used to reach for a metaclass to do, with far less complexity: Base __init_subclass__ class A(Base) <rect class='d-box' x='20' y='102

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Hook for subclass creation.

oopinit-subclass

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PYAuto-register and validate subclasses

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