> Maybe if you explicitly ask for the "sign" of a NaN, it should
> always be a space.
Actually, I think '+nan' for format(float('nan'), '+'), and ' nan'
for format(float('nan'), ' '). Then nans and infs can be treated
identically, except that the sign of a nan is always considered to be
positive, regardless of what the _Py_dg_dtoa function returns.
> And when requesting leading zeros, you also get leading spaces
> instead?
Should do the same thing for nans and infs here. But certainly leading
zeros should be avoided. Leading spaces sounds fine to me.