Order units

[SpazzNon]

Hi, when I multiply units of force with length or its simplification results in force times length the result always gives in order length times force, I would like that to change because I am using handcalcs and generate reports so it is unusual to read length times force, when I am used to it being force times length. Attached is the configuration.

from IPython.display import Latex

import handcalcs.render
import pandas as pd
pd.options.display.float_format = "{:.2f}".format
from math import sqrt, sin, tan, pi,cos
import pint
un = pint.UnitRegistry(auto_reduce_dimensions=True)
preferred_units = [
    un.m,
    un.kg,
    un.s, 
    un.K,
    un.kN,
    un.W,
    un.kip,
]

un.default_preferred_units = preferred_units
un.define('tonf = 1000 * kg * 9.80665 * m / s**2')
un.define('kgf = 1 * kg * 9.80665 * m / s**2')
#un.define('ksi = 1 * kg * 1* m / s**2*6894757.29316836/m**2')
un.define('ksi = 1 * kip / inch**2')

m= un.m
mm= un.mm
inch = un.inch
MPa = un.MPa
tonf= un.tonf
kgf= un.kgf
cm = un.cm
ksi = un.ksi
kip = un.kip
lb= un.lb
ft= un.ft
N= un.N

un.default_preferred_units = preferred_units
handcalcs.set_option("preferred_string_formatter", "~L")```

[andrewgsavage]

this is possible, here's an example. it needs adding to the documentation.

>>> import pint
>>> ur = pint.UnitRegistry()
>>> ur.formatter.dim_order
('[substance]', '[mass]', '[current]', '[luminosity]', '[length]', '[]', '[time]', '[temperature]')
>>>
>>> from pint.delegates.formatter._compound_unit_helpers import sort_by_dimensionality
>>> ur.formatter.default_sort_func = sort_by_dimensionality
>>>
>>> Q_=ur.Quantity
>>> res=Q_(1,"m")*Q_(1,"N")
>>> str(res)
'1 newton * meter'
>>>
>>> ur.formatter.dim_order = ('[temperature]', '[time]', '[]', '[length]', '[luminosity]', '[current]', '[mass]', '[substance]')
>>>
>>> Q_=ur.Quantity
>>> res=Q_(1,"m")*Q_(1,"N")
>>> str(res)
'1 meter * newton'
>>>

[SpazzNon]

this is possible, here's an example. it needs adding to the documentation.

>>> import pint
>>> ur = pint.UnitRegistry()
>>> ur.formatter.dim_order
('[substance]', '[mass]', '[current]', '[luminosity]', '[length]', '[]', '[time]', '[temperature]')
>>>
>>> from pint.delegates.formatter._compound_unit_helpers import sort_by_dimensionality
>>> ur.formatter.default_sort_func = sort_by_dimensionality
>>>
>>> Q_=ur.Quantity
>>> res=Q_(1,"m")*Q_(1,"N")
>>> str(res)
'1 newton * meter'
>>>
>>> ur.formatter.dim_order = ('[temperature]', '[time]', '[]', '[length]', '[luminosity]', '[current]', '[mass]', '[substance]')
>>>
>>> Q_=ur.Quantity
>>> res=Q_(1,"m")*Q_(1,"N")
>>> str(res)
'1 meter * newton'
>>>

Thank you very much for your prompt reply; I tried it with your proposal and it worked perfectly, but when I tried it with ‘inch’ and ‘kip’ and it stopped working, the ‘inch’ is always put in front and I don't understand why.

[andrewgsavage]

the function sort_by_dimensionality ordered based on the index of the dimensionality of each unit in the dim_order tuple, see

pint/pint/delegates/formatter/_compound_unit_helpers.py

Line 199 in b436902

def sort_by_dimensionality(

you could write your own function to sort in the way you desire. see the sort_by_dimensionality for an example

this would be something good to add to pint; the functionality to provide a list of units and a function that sorts based on that list, analagous to the dim_order