Class emulating numeric behaviour with Pint quantities

[nopria]

I wrote a custom Point class which I'd like to work with Pint quantities but I get a strange error if I try to emulate numeric behaviour:

import pint
um = pint.get_application_registry()

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def __add__(self, other):
        if isinstance(other, pint.Quantity):
            return Point(self.x + other, self.y + other)
        return NotImplemented
    def __radd__(self, other):
        if isinstance(other, pint.Quantity):
            return Point(self.x + other, self.y + other)
        return NotImplemented

q = 0.03 * um.m
p = Point(10 * um.mm, 2 * um.cm)

p + q works correctly as expected, while q + p gives the followong error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\UP\miniconda3\lib\site-packages\pint\facets\plain\quantity.py", line 841, in __add__
    return self._add_sub(other, operator.add)
  File "C:\Users\UP\miniconda3\lib\site-packages\pint\facets\plain\quantity.py", line 103, in wrapped
    return f(self, *args, **kwargs)
  File "C:\Users\UP\miniconda3\lib\site-packages\pint\facets\plain\quantity.py", line 739, in _add_sub
    raise DimensionalityError(self._units, "dimensionless")
pint.errors.DimensionalityError: Cannot convert from 'meter' to 'dimensionless'

Any clue? Thanks in advance.

[andrewgsavage]

add Point to pint.compat.upcast_type_map

see #1888

[nopria]

I did

pint.compat.upcast_type_map.update({'Point':None})

but nothing changes.

[andrewgsavage]

try
pint.compat.upcast_type_map.update({'__main__.Point':None})

[hgrecco]

Shall we probide a register_upcast_type function or similar that does the right thing in relation to naming?

[nopria]

In this specific MWE the last above solution works, but in my actual code Pint is not imported in the same script where class Point is defined but in a separate module tools which is imported by import tools as tls. With such configuration just adding

pint.compat.upcast_type_map.update({'__main__.Point':None})

to tools.py does not work. Moreover, Point is a subclass of Geotools, maybe this affects the instruction needed to solve my issue?

[andrewgsavage]

Run type(object) and it will give the string you should use. For the example above I did

type(p)
__main__.Point

[nopria]

Now it works, thanks.