rate removed, caused divide by zero on empty file

        begin = kwargs.get('begin')

        end   = kwargs.get('end')

        itau, iphase = get_tau_index(begin)

        rate = int(len(data['lambda'])/data['pcharge']*1e12) # rate per picoCoulomb

        self.tau.setdefault(itau, [])

        if not self.tau[itau]:

            self.log.info("%s: processing tau=%2d", filename, itau)

        self.log.debug("tau:phase=%2d:%3d index=%4d (%10.3f - %10.3f)   %10.3eC %7.4f %10d",

                        itau, iphase, begin['value'], begin['time'], end['time'],

                        data['pcharge'], data['phase'], rate)

                        data['pcharge'], data['phase'])

        data['iphase'] = iphase

        self.tau[itau].append(data)

        return True