GroupInstantiationError

Symptom

Raised naming the Group subclass someone tried to instantiate, saying it cannot be created as an object.

Cause

A Group subclass was called like a constructor (MyGroup()). Groups are namespaces for declaring providers as class attributes — they're never meant to be instantiated, only passed by class reference to Container(groups=[MyGroup]) or read via MyGroup.some_provider.

Fix

Use the class itself, not an instance:

class Dependencies(Group):
    service = providers.Factory(Service, scope=Scope.APP)


# Wrong
deps = Dependencies()             # raises GroupInstantiationError

# Right
container = Container(groups=[Dependencies])
service = container.resolve_provider(Dependencies.service)

This usually happens from a habit carried over from frameworks where a container/module is instantiated, or from accidentally writing Dependencies() instead of Dependencies in a type annotation or default value.

See also

• Multi-Group organization — organizing providers across several Group classes.