Package: django-pint
Django Quantity FieldA Small django field extension allowing you to store quantities in certain units and perform conversions easily. Usespintbehind the scenes. Also contains a form field class and form widget that allows a user to choose alternative units to input data. The cleaned_data will output the value in the base_units defined for the field, eg: you specify you want to store a value in grams but will allow users to input either grams or ounces.Help wantedI am currently not working with Django anymore. Therefore the Maintenance of this project is not a priority for me anymore.
If there is anybody that could imagine helping out maintaining the project, send me a mail.CompatibilityRequires django >= 3.2, and python 3.8/3.9/3.10/3.11Tested with the following combinations:Django 3.2 (Python 3.8, 3.9, 3.10, 3.11)Django 4.2 (Python 3.8, 3.9, 3.10, 3.11)Installationpip install django-pintSimple ExampleBest way to illustrate is with an example# app/models.py

from django.db import models
from quantityfield.fields import QuantityField

class HayBale(models.Model):
    weight = QuantityField('tonne')Quantities are stored as float (Django FloatField) and retrieved like any other field>> bale = HayBale.objects.create(weight=1.2)
>> bale = HayBale.objects.first()
>> bale.weight
<Quantity(1.2, 'tonne')>
>> bale.weight.magnitude
1.2
>> bale.weight.units
'tonne'
>> bale.weight.to('kilogram')
<Quantity(1200, 'kilogram')>
>> bale.weight.to('pound')
<Quantity(2645.55, 'pound')>If your base unit is atomic (i.e. can be represented by an integer), you may also useIntegerQuantityFieldandBigIntegerQuantityField.If you prefer exact units you can use theDecimalQuantityFieldYou can also pass Quantity objects to be stored in models. These are automatically converted to the units defined for the field
( but can be converted to something else when retrieved of course ).>> from quantityfield.units import ureg
>> Quantity = ureg.Quantity
>> pounds = Quantity(500 * ureg.pound)
>> bale = HayBale.objects.create(weight=pounds)
>> bale.weight
<Quantity(0.226796, 'tonne')>Use the inbuilt form field and widget to allow input of quantity values in different unitsfrom quantityfield.fields import QuantityFormField

class HayBaleForm(forms.Form):
    weight = QuantityFormField(base_units='gram', unit_choices=['gram', 'ounce', 'milligram'])The form will render a float input and a select widget to choose the units.
Whenever cleaned_data is presented from the above form the weight field value will be a
Quantity with the units set to grams (values are converted from the units input by the user).
You also can add theunit_choicesdirectly to theModelField. It will be propagated
correctly.For comparative lookups, query values will be coerced into the correct units when comparing values,
this means that comparing 1 ounce to 1 tonne should yield the correct results.less_than_a_tonne = HayBale.objects.filter(weight__lt=Quantity(2000 * ureg.pound))You can also use a custom Pint unit registry in your projectsettings.py# project/settings.py

from pint import UnitRegistry

# django-pint will set the DJANGO_PINT_UNIT_REGISTER automatically
# as application_registry
DJANGO_PINT_UNIT_REGISTER = UnitRegistry('your_units.txt')
DJANGO_PINT_UNIT_REGISTER.define('beer_bootle_weight = 0.8 * kg = beer')

# app/models.py

class HayBale(models.Model):
    # now you can use your custom units in your models
    custom_unit = QuantityField('beer')Note: As thedocumentation from pintstates quite clearly: For each project there should be only one unit registry.
Please note that if you change the unit registry for an already created project with
data in a database, you could invalidate your data! So be sure you know what you are
doing!
Still only adding units should be okay.DevelopmentPreparationYou need to install all Python Version that django-pint is compatible with.
In a *nix environment you best could usepyenvto do so.Furthermore, you need to installtoxandpre-committo lint and test.You also need docker as our tests require a postgres database to run.
We don't use SQL lite as some bugs only occurred using a proper database.I recommend usingpipxto install them.Installpipx(see pipx documentation), i.e. withpython3 -m pip install --user pipx && python3 -m pipx ensurepathInstallpre-commitrunningpipx install pre-commitInstalltoxrunningpipx install toxInstall thetox-dockerpluginpipx inject tox tox-dockerForkdjango-pintand clone your fork (seeTutorial)Change into the repocd django-pintActivatepre-commitfor the repo runningpre-commit installCheck that all linter run fine with the cloned version by runningpre-commit run --all-filesCheck that all tests succeed by runningtoxCongratulationyou successfully cloned and tested the upstream version ofdjango-pint.Now you can work on your feature branch and test your changes usingtox.
Your code will be automatically linted and formatted bypre-commitif you commit your changes.
If it fails, simply add all changes and try again.
If this doesn't help look at the output of yourgit commitcommand.Once you are done,create a pull request.Local development environment with DockerTo run a local development environment with Docker you need to run the following steps:
This is helpful if you have troubles installingpostgresqlorpsycopg2-binary.git cloneyour forkruncp .env.example .envedit.envfile and change it with your credentials ( the postgres host should match the service name in docker-file so you can use "postgres" )runcp tests/local.py.docker-example tests/local.pyrundocker-compose upin the root folder, this should build and start 2 containers, one for postgres and the other one python dependencies. Note you have to be in thedockergroup for this to work.open a new terminal and rundocker-compose exec app bash, this should open a ssh console in the docker containeryou can runpytestinside the container to see the result of the tests.Updating the packagePythonandDjangomajor versions have defined EOL.
To reduce the maintenance burden and encourage users to use version still receiving security updates anydjango-pintupdate should match all and only these version of Python and Django that are supported.
Updating these dependencies have to be done in multiple places:README.md: Describing it to end userstox.ini: For local testingsetup.cfg: For usage with pip and displaying it in PyPa.github/workflows/test.yaml: For the CI/CD Definition