Parameter.__getitem__ behavior about qcodes HOT 5 OPEN

Ah, apologies for not searching for an existing issue. I don't actually use the functionality, so I'm all for keeping Parameter simple.

I can open up a PR for validation in register_parameter, but it's only putting out one small fire compared to the proper solution in #5036.

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@thangleiter I think we should reopen since we have only resolved this partially? Do you agree

I guess it makes sense to keep it open for bookkeeping. The last of the examples above is indeed not fixed by #6084.

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Thinking a bit more about this my proposed solution is.

• Add sweep and __getitem__ above to a new Sweeper class in qcodes-loop and update all of that pacakge to make use of this.
• Cut a new release of qcodes-loop
• Deprecate these two methods

from qcodes.

It should indeed be deprecated see #5036

__getitem__ and parameter.sweep (which already exists) are both remaining leftovers of qcodes_loop in qcodes that I have not yet found a clean way to get rid of without breaking that package.

We are not planning to introduce any sweep functionality into the parameter to use with qcodes.dataset but parameters can be sweep by passing them to LinSweep and friends. This choice is made since

• The parameter class is already too complicated and does too many things
• Having the sweeper externally gives greater flexibility in implementing different sweep strategies.

I however, agree that it would be great to have better validation in register_parameter to error early if setpoints is a ParameterBase subclass. A pr for that is most welcome.

from qcodes.

@thangleiter I think we should reopen since we have only resolved this partially? Do you agree

from qcodes.