TypeError: unsupported operand type(s) for -: 'Decimal' and 'Decimal'. Why?

[Zentrader]

> from decimal import Decimal
>
> In [21]: a = Decimal()
>
> In [22]: class Decimal(object):
>    ....:     pass
>    ....:
>
> In [23]: b = Decimal()
>
> In [24]: a - b

Perhaps I don't understand what you are doing here, but on line 22 you
overload Decimal.  If you just have
a = Decimal()
b = Decimal()
print a-b yields 0.  decimal.Decimal() can be subtracted from
decimal.Decimal().  decimal.Decimal() can not be subtracted from class
Decimal(object).  I would assume that they are different types.  Using
the original code, print type(a), type(b).