def get_nu(isp, rxn):
    """Returns the net nu of species isp for the reaction rxn

    Parameters
    ----------
    isp : int
        Species index
    rxn : `ReacInfo`
        Reaction

    Returns
    -------
    nu : int
        Overall stoichiometric coefficient of species ``isp`` in reaction ``rxn``

    """
    if isp in rxn.prod and isp in rxn.reac:
        nu = (rxn.prod_nu[rxn.prod.index(isp)] -
              rxn.reac_nu[rxn.reac.index(isp)])
        # check if net production zero
        if nu == 0:
            return 0
    elif isp in rxn.prod:
        nu = rxn.prod_nu[rxn.prod.index(isp)]
    elif isp in rxn.reac:
        nu = -rxn.reac_nu[rxn.reac.index(isp)]
    else:
        # doesn't participate in reaction
        return 0
    return nu