Python – pint – Can I set default type to Decimal?

Question

Im using pint module in a project. Objects in my project handle numerical data as Decimals. When I set simple pint units to a Decimal, it works:

>>> import pint
>>> from decimal import Decimal as D
>>> ureg = pint.UnitRegistry()
>>> D(10) * ureg.kN
<Quantity(10, 'kilonewton')>

But, if I try to add a second unit, it breaks. Building kiloNewton*meters in this example:

>>> D(10) * ureg.kN * ureg.m
TypeError: unsupported operand type(s) for *: 'decimal.Decimal' and 'float'

I’m using this hack:

>>> a = D(1) * ureg.kN
>>> b = D(1) * ureg.m
>>> unit_kNm = a * b
>>> D(10) * unit_kNm
<Quantity(10, 'kilonewton * meter')>

I understand why it happens. I’m looking for a solution to set up pint as I want.

Asked By: echefede

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Source

Answer 1

Type cast it to decimal

import decimal
D(10) * ureg.kN * decimal.Decimal(ureg.m)

Answered By: Vishnu Upadhyay

Answer 2

This works:

>>> D(10) * (ureg.kN * ureg.m)
<Quantity(10, 'kilonewton * meter')>

And this too:

>>> Q = ureg.Quantity
>>> Q(D(10), "kN*m")
<Quantity(10, 'kilonewton * meter')>

Answered By: echefede

Answer 3

As version 0.11 of pint, you can create UnitRegistry with the non_int_type=Decimal options. All new quantities created with this UnitRegistry instance have their value represented by a Decimal instance.

Example:

import pint
from decimal import Decimal
ureg = pint.UnitRegistry(non_int_type=Decimal)
a = ureg.Quantity("5 meter")
print(type(a.magnitude))

This will show that the magnitude is of type <class 'decimal.Decimal'>.

Answered By: Toon Verstraelen

Python – pint – Can I set default type to Decimal?

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