> It's a warning but not a fatal error. It can't hurt to just support it.

Ahh so if it is a warning then you should use the Python warnings module,
rather than printing.  With printing the end user has no way
of suppressing the output, but with warnings there are a lot more options.
http://docs.python.org/2/library/warnings.html

On Fri, Jan 11, 2013 at 1:10 AM, Elliott Biondo <notifications@github.com>wrote:

> In pyne/material.pyx:
>
> > +
> > +    ''' Check to see it material is definted my mass or atom fracs.
> > +         If atom fracs, convert. '''
> > +    mass_bool = False # boolean to describe whether mass fractions are used
> > +    atom_bool = False # boolean to describe whether atom fractions are used
> > +    for key, value in nucvec.items() :
> > +        if value < 0 :
> > +           mass_bool = True
> > +        else:
> > +            atom_bool = True
> > +    try:
> > +        mass_bool != atom_bool
> > +    except ValueError :
> > +        print 'Mixed atom and mass fractions not suppported.\
> > +               See material defined on line {0}'.format(mat_line)
> > +
>
> It's a warning but not a fatal error. It can't hurt to just support it.
>
> —
> Reply to this email directly or view it on GitHub<https://github.com/pyne/pyne/pull/100/files#r2615168>.
>
>