reduce_units?

[rwijtvliet]

Using these definitions:

#unitdefinitions.txt

mega- = 1e6 = M-

### Base dimensions and their units. Base unit without prefix. ###

# Dimensionless
fraction = []

# Duration (Time)
hour = [time] = h = hr

# Energy
watthour = [energy] = Wh

# Revenue (Currency)
euro = [currency] = Eur = €

### Derived dimensions and their units. ###

# Power
[power] = [energy] / [time]
watt = watthour / hour = W

# Price
[price] = [currency] / [energy]
euro_per_MWh = euro / (1_000_000 * watthour)  = Eur/MWh

I often get into a situation where a quantity has redundant units, even though auto_reduce_dimensions is set to True. For example:

 import pint
 ureg = pint.UnitRegistry(str(path), auto_reduce_dimensions=True)
 
power = ureg.Quantity(5, 'MW')
duration = ureg.Quantity(2, 'h')
price = ureg.Quantity(1, 'Eur/MWh')
revenue = power * duration * price # in euros

revenue
<Quantity(10, 'megawatt * hour * euro / megawatthour')>   # wat

revenue.dimensionality
<UnitsContainer({'[currency]': 1})> # as expected

Is there an issue with my config?

I know I can do revenue.to('Eur'), but I'd like to avoid having to do this.

[andrewgsavage]

https://pint.readthedocs.io/en/stable/getting/tutorial.html#simplifying-units

There are also methods to_reduced_units() and ito_reduced_units() which perform a simplified dimensional reduction, combining units with the same dimensionality but otherwise keeping your unit definitions intact.

it'll reduce m and mm. megawatt * hour are treated as MW and hour, which have different dimensionality to megawatthour so won't reduce

try using to_base_units or to_preffered

[rwijtvliet]

Thanks for that fast reply. I think to_preferred is actually what I want.

One follow-up question if I may, as I cannot find it in the docs.

If I set autoconvert_to_preferred=True when initialising a unit registry - where do I specify, what those preferred units are?

[andrewgsavage]

It's in the docs, ureg.default_preferred_units

…

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