CODEWITHSUNDEEP
pythonmicropython
Bob
Bob

Reputation: 4970

how to reference previous arguments of a function call in later arguments?

This is in micropython

I'm creating an API to control some hardware. The API will be implemented in C with an interface in micropython.

One example of my API is:

device.set(curr_chan.BipolarRange, curr_chan.BipolarRange.state.ON)

I'd like to be able to achieve the same functionality but shorten the second path by somehow implicitly referencing the first argument:

device.set(curr_chan.BipolarRange, <first arg?>.state.ON)

Is there anyway to do this?

The only way to do something like this now would be 

device.set(curr_chan.BipolarRange.state.ON)

and then put an upward pointing C-pointer on both the ON C-object and state C-object so that I know which entry in curr_chan is being referenced.

The micropython runtime - and I assume CPython one - doesn't keep the entire object "tree" available to the developer in memory.

Upvotes: 1

Views: 198

Answers (2)

Mad Physicist
Mad Physicist

Reputation: 114330

Pass the name of the attribute you want as the second argument. Call getattr (or PObject_GetAttr repeatedly to get each element of the .-separated string:

device.set(curr_chan.BipolarRange, 'state.ON')

Upvotes: 1

Florian Weimer
Florian Weimer

Reputation: 33719

You could have special values for the second (state) argument which tell the function implementation to derive the state from the first argument. You could also introduce a completely separate function which has this behavior.

Or you could have a helper function which determines the state and passes it down to the set function, something like this:

device.set(*state_ON(curr_chan.BipolarRange))

Here, state_ON would return a tuple (curr_chan.BipolarRange, curr_chan.BipolarRange.state.ON).

In any case, there is no direct support for what you are trying to do in Python itself.

Upvotes: 1

Related Questions