Why litre dimensionality is length and not volume?

[lipemorais]

I'm working on setting a feature to check the dimensionality of some units of measure, but I get length as the dimensionality for litre, ml as well. Why is that? Should it be volume? How could I get volume as unit of measure for it?

[dopplershift]

import pint

ureg = pint.UnitRegistry()
x = 3 * ureg('mL')
x.dimensionality

gives <UnitsContainer({'[length]': 3})>, which says the dimensionality is length**3, which implies volume?

[lipemorais]

Hmm, got you I was expecting it to be something like <UnitsContainer({'[volume]': 1})>

[andrewgsavage]

Have a play with #1967 It needs reviewing and feedback.
With that PR,

import pint

ureg = pint.UnitRegistry()
x = 3 * ureg('mL')
x.compatible_kinds()
{'[volume]'}

I'm working on setting a feature

Could you expand on this? Understanding how you intend to use this could help make test cases.