Generalized params update function

update_user_params.py

def update_params(params):
    # update params if user said 'auto', otherwise take user specified value
    # a first try at reusing for all params the same code for that logic
    for param_key, param_value in params.items():
        actual_key = 'actual_' + param_key
        # Is this a param that has a user mode?
        has_user_mode = actual_key in params
        if has_user_mode:
            if param_value is 'user-forced':
                # we could even do more checks here, maybe param-specific
                assert params[actual_key] is not None
                # just copy the user specified value to the actual
                params[actual_key] = param_value
            elif param_value is 'auto':
                # debatable, we could just overwrite silently (but I prefer to assert)
                assert params[actual_key] is None
                # this is major change: need a compute_derived_param for all params separately
                # makes things cleaner?
                params[actual_key] = compute_derived_param(params, param_key, param_value)
            else:
                raise ValueError("unsupported value {} in param key: {}. Needs to be 'auto' "
                                 "or 'user-forced'.".format(param_value, param_key))


def compute_derived_param(params, param_key, param_value):
    # probably better to have a complete separate function per param update
    if param_key is 'az_aperture':
        return [1, 2, 3]


def test_update_params():
    user_params = dict(
        # legacy style: just the value
        tx_frequency=4 * units.megahertz,

        # new style: user-forced
        depth='user-forced',
        actual_depth=3,

        # new style: auto
        az_aperture='auto',
        actual_az_aperture=None,
    )

    updated_params = update_params(user_params)

    assert(user_params['tx_frequency'] == updated_params['tx_frequency'] == 4 * units.megahertz)
    assert(user_params['depth'] == 'user-forced')
    assert(user_params['actual_depth'] == 3)
    assert(user_params['az_aperture'] == 'auto')
    assert(user_params['actual_az_aperture'] == [1, 2, 3])