Apply a func to a target class to any fields and items nested within an object

nested_map.py

def nested_map(obj: object, func, target_class) -> Any:
    """
    Accepts any object type and calls .func() on any nested fields of the specified class.
    """
    def _nested_map(obj: object) -> None:
        """
        Traverse all object fields and list items, calling func when possible.
        """
        # Objects without __dict__ cannot have vars() called
        if not hasattr(obj, '__dict__'):
            return

        for field in vars(obj):
            field_data = getattr(obj, field)
            # Easy case, call func
            if isinstance(field_data, target_class):
                setattr(obj, field, field_data.func())
            # List types need to have each item recursively called
            elif isinstance(field_data, list):
                [_nested_map(item) for item in field_data]
            # Nested object needs to be recursively called
            elif hasattr(field_data, '__dict__'):
                _nested_map(field_data)

    # Without copying the object we might mutate constant fields depending on the func param
    obj = deepcopy(obj)
    _nested_map(obj)

    return obj