Mark Dickinson <report@bugs.python.org> wrote:
> On what grounds is it a bug?  I might call it a poor design decision,
> but it's clearly intentional. There's even a unit test for it.

Maybe "bug" is not the right word. I'd call it a deviation from the
specification then. Do you happen to know what the intention was?

If from_tuple(..., 'F') accepts coefficients, logically Decimal("Infinity0"),
Decimal("Infinity123") etc. should be accepted as well. But they're not part
of the grammar and decimal.py rejects them.

http://speleotrove.com/decimal/daconvs.html