How to determine if a quantity is a scalar or a list

[edmundsj]

So I am trying to check if a quantity is a scalar or a list, and in each case, I want to treat them differently. However, they appear to have the same type (pint.Quantity), which makes this impossible without a try/except block. Normally I would do something like isinstance(quantity, quantity_array). Even scalar-valued quantities have the len method implemented, so I can't use this as a check. Is there an easier way than this (below)?

import pint
ureg = pint.UnitRegistry()
qt = 1.0 * ureg.mV

try:
    len(qt)
    print("This is a list")
except:
    print("This is a scalar")

It seems awkward and like there should be an easier way.

[edmundsj]

It looks like the magnitude of the quantity retains its original type, so my solution is the following:

import pint
ureg = pint.UnitRegistry()
qt = 1.0 * ureg.mV

if isinstance(qt.magnitude, (list, np.ndarray)):
    print("This is a list")
else:
    print("This is a scalar")

This is still a little awkward, because I have to do two checks: first if the object is a quantity, and then if its magnitude is a list (instead of just checking if the object is a list of quantities, whatever that type may be). My objects could be vanilla lists, in which case they won't have a magnitude and the code above will throw an error. It would be nice to do something like:

import pint
ureg = pint.UnitRegistry()
qt = 1.0 * ureg.mV

if isinstance(qt pint.QuantityArray):
    print("This is a list")
else:
    print("This is a scalar")

[hgrecco]

Pint (currently) wraps (not subclass) numerical classes. But there is long standing discussion if we should move to subclassing numpy.ndarray or makeing two subclass QuantityScalar/QuantityArray. See #1128 and similars