probe.py

class Probe:
    required_string = ['type']
    string = ['probe_manufacturer', 'probe_serial_number', 'probe_tag',
        'wedge_manufacturer', 'wedge_serial_number', 'wedge_tag']
    required_other = ['element_position', 'element_minor', 'element_major',
        'element_shape', 'centre_frequency']
    other = ['element_radius_of_curvature', 'element_axis_of_curvature',
        'wedge_surface_point', 'wedge_surface_normal', 'dead_element',
        'bandwidth']

    def __init__(self, probe_dataset):
        self._probe = probe_dataset

    def __getattr__(self, name):
        if name in Probe.required_string:
            return self._probe[name].decode('ascii')
        elif name in Probe.required_other:
            return self._probe[name]

        try:
            if name in Probe.string:
                return self._probe[name].decode('ascii')
            elif name in Probe.other:
                return self._probe[name]
        except KeyError:
            raise OptionalKey("Optional key")

        raise AttributeError("No such data field")

Some of these are attributes, so need accessed using probe.attrs.