Why is functools.partial used so frequently?

[jordandsullivan]

In a fair number of example notebooks and tests, the utility functools.partial is used to creator an executor function with fewer arguments specific arguments set to particular values. e.g. https://github.com/unitaryfund/mitiq/blob/main/docs/source/examples/ddd_tutorial.md?plain=1#L182.

If this is such a common use case (creating executors which accept a smaller number of arguments), why not advise users to use optional positional arguments with sensible defaults? Why the need to create a whole new executor function using functools.partial?

[jordandsullivan]

Upon further reflection, I suppose it is a convenient way to specify positional arguments that will stay the same across many executions of a function.

[natestemen]

Yup that's exactly it!

Since users can pass both python functions, and Executor objects into Mitiq, we could potentially add a method that returns a new executor with the specified kwargs. E.g. this could look like the following.

def execute(circuit, noise_level=100, shots=1000):
    ...

executor = Executor(execute)

executor_with_more_shots = executor.set_params(shots=10_000)

I think most users of Mitiq are now using an Executor object, however, as it's not required.

[jordandsullivan]

I may be wrong, but it doesn't look like the usage of partial is explained anywhere in our documentation, although it is used in multiple examples. I think it might be useful to add a short description and example to the Executors page in our docs.

Created an issue for it: #2360

[natestemen]

Makes sense. Since we have an issue open to track this now, feel free to close this discussion.