TypeError: unsupported operand type(s) for *: 'float' and 'Decimal'

[danielsokolowski]

I have only traced the bug on surface so I do not understand why this method is called UnitRegistry.convert(...). In a nut shell, using Decimal magnitude as opposed to float causes this method to fail as it tried to multiply Decimal and floats together - below is the stack trace.

>>> Offer(product=Product.objects.get(pk=1), amount_min='1000 kg', user=User.objects.get(pk=1), company=Company.objects.get(pk=1)).full_clean()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-ticket_20625-tailored/django/db/models/base.py", line 923, in full_clean
    self.clean_fields(exclude=exclude)
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-ticket_20625-tailored/django/db/models/base.py", line 965, in clean_fields
    setattr(self, f.attname, f.clean(raw_value, self))
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-ticket_20625-tailored/django/db/models/fields/__init__.py", line 256, in clean
    self.run_validators(value)
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-ticket_20625-tailored/django/db/models/fields/__init__.py", line 202, in run_validators
    if value in self.empty_values:
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/quantity.py", line 347, in __eq__
    return self.dimensionless and _eq(self.magnitude, other)
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/quantity.py", line 153, in dimensionless
    tmp = copy.copy(self).to_base_units()
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/quantity.py", line 210, in to_base_units
    ret.ito_base_units()
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/quantity.py", line 201, in ito_base_units
    self._magnitude = self._REGISTRY.convert(self._magnitude, self._units, other)
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/unit.py", line 674, in convert
    # Clone and put on Python path: https://github.com/tenXer/PyDevSrc, place this in your settings_development.py, and place your 'break' points in Eclipse
TypeError: unsupported operand type(s) for *: 'float' and 'Decimal'

[hgrecco]

This was always very confusing for me but is the standad in Python 2

Python 2.7.2 |CUSTOM| (default, Jul 27 2011, 13:29:32)
[GCC 4.0.1 (Apple Inc. build 5493)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import decimal
>>> decimal.Decimal(10) * 10.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for *: 'Decimal' and 'float'

and in Python 3

Python 3.2.3 (v3.2.3:3d0686d90f55, Apr 10 2012, 11:25:50)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import decimal
>>> decimal.Decimal(10) * 10.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for *: 'Decimal' and 'float'

[danielsokolowski]

Hi @hgrecco, yes I am aware of that - but the issue is with pint itself - I'll clarify below and the tentative fix is to follow:

>>> import pint
>>> from decimal import Decimal
>>> q = pint.UnitRegistry().Quantity(Decimal('1000'), 'kg')
>>> q
<Quantity(1000, 'kilogram')>
>>> q.to_base_units()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/quantity.py", line 210, in to_base_units
    ret.ito_base_units()
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/quantity.py", line 201, in ito_base_units
    self._magnitude = self._REGISTRY.convert(self._magnitude, self._units, other)
  File "/srv/www/django/development.<hidden>/src/github-danielsokolowski-django-unitofmeasure/unitofmeasure/danielsokolowski-pint/pint/unit.py", line 677, in convert
    """Builds dimensionless quantities using the Buckingham Ï theorem
TypeError: unsupported operand type(s) for *: 'float' and 'Decimal'

[danielsokolowski]

Here is the pull request: #48

[hgrecco]

You are right. I should not have closed the issue. Thanks!

[danielsokolowski]

Sweet - thanks!