Q_ triggers a warning when using as_compact

[vhirtham]

When running the following script:

from weldx import Q_
from pint import Quantity

Q_(1000000020.,"s").to_compact()

I get the following warning:

RuntimeWarning: to_compact applied to non numerical types has an undefined behavior.
  Q_(1000000020.,"s").to_compact()

and the "wrong" unmodified output:

1000000020.0
s

Exchanging Q_ with Quantity removes the warning and the output is as wanted:

1.00000002 gigasecond

Here is the corresponding exception block at the beginning of the implementation from to_compact:

if not isinstance(self.magnitude, numbers.Number):
            msg = (
                "to_compact applied to non numerical types "
                "has an undefined behavior."
            )
            w = RuntimeWarning(msg)
            warnings.warn(w, stacklevel=2)
            return self

Guess it has something to do with our custom additions.

[CagtayFabry]

As mentioned I guess this is because handling arrays that cover a wide magnitude range of values are not so easy to assign a 'compact' unit.
Our unit registry is configured to convert all values to arrays (even scalars) which is why it never works with Q_

we could implement this ourselves in some way but I am fine not having this functionality for now

[vhirtham]

As mentioned I guess this is because handling arrays that cover a wide magnitude range of values are not so easy to assign a 'compact' unit. Our unit registry is configured to convert all values to arrays (even scalars) which is why it never works with Q_

we could implement this ourselves in some way but I am fine not having this functionality for now

It is not super important. A simple fix that would at least work for the tutorials is to override the function and turn length=1 arrays back into a number type and then pass the new quantity to the parent class function.