def produce_period(self,*args,**kwargs):
        '''
            return the period grid based on actual sizes.
            frequency of zero --> period 0.  what else to do?
        '''
        f2T = self.produce_frequency(*args,**kwargs)
        for i in range(1,len(f2T)):
            f2T[i] = 1/f2T[i]
        return f2T

            return the period grid based on actual sizes.
            frequency of zero --> period 0.  what else to do?
        
recipes/Python/576550_gsl_real_fft_in_python3/recipe-576550.py