Remove index entry from parsed CSA header elements

[matthew-brett]

Am I right in thinking that the index elements in a CSA header are always sequential?

For example, from the README:

{
    'NumberOfPrescans': {'index': 1, 'VR': 'IS', 'VM': 1, 'value': 0},
    'TransmitterCalibration': {'index': 2, 'VR': 'DS', 'VM': 1, 'value': 247.102},
    'PhaseGradientAmplitude': {'index': 3, 'VR': 'DS', 'VM': 1, 'value': 0.0},
    'ReadoutGradientAmplitude': {'index': 4, 'VR': 'DS', 'VM': 1, 'value': 0.0},
    'SelectionGradientAmplitude': {'index': 5, 'VR': 'DS', 'VM': 1, 'value': 0.0},
...
}

Are these index entries necessary? I realize they are in the CSA header structure, but, given Python dictionary insertion order, does:

indices = [v['index'] for k, v in parsed_csa.items()]

ever differ from np.arange(len(parsed_csa))?

[ZviBaratz]

Yeah, they definitely don't seem to be necessary. However, it might be a good idea to use OrderedDict to make sure order is preserved.

[matthew-brett]

Does OrderedDict preserve order better than dict in Python >= 3.7?

[ZviBaratz]

AFAIK, yes. OrderedDict still guarantees the order of the dictionary items in ways that dict does not.

[matthew-brett]

This page lists the advantages of OrderedDict as:

• OrderedDict makes it clear that the order of items in the dictionary is important.
• Features for control over the order of items - you can use .move_to_end and .popitem(last=False)
• Compare equal iff elements are in same order.

[ZviBaratz]

I see. Well, in that case, I guess dict would be good enough.