def Planck_frequency(nu, T):
    '''The Planck function B(nu,T):
    the flux density for blackbody radiation in frequency space
    nu is frequency in 1/s
    T is temperature in Kelvin

    Formula (3.1) from Raymond Pierrehumbert, "Principles of Planetary Climate"
    '''
    return 2*hPlanck*nu**3/c_light**2/(exp(hPlanck*nu/kBoltzmann/T)-1)
def Planck_frequency ( nu , T ) : return 2 * hPlanck * nu ** 3 / c_light ** 2 / ( exp ( hPlanck * nu / kBoltzmann / T ) - 1 )
The Planck function B(nu,T):
    the flux density for blackbody radiation in frequency space
    nu is frequency in 1/s
    T is temperature in Kelvin

    Formula (3.1) from Raymond Pierrehumbert, "Principles of Planetary Climate"