def pws_constants(t):
    'Lookup-table for water vapor saturation pressure constants (A, m, Tn).'
    if (t < (- 20)):
        raise ValueError('Temperature out of range (-20 - 350°C')
    if (t < 50):
        return (6.116441, 7.591386, 240.7263)
    if (t < 100):
        return (6.004918, 7.337936, 229.3975)
    if (t < 150):
        return (5.856548, 7.27731, 225.1033)
    if (t < 200):
        return (6.002859, 7.290361, 227.1704)
    return (9.980622, 7.388931, 263.1239)
Lookup-table for water vapor saturation pressure constants (A, m, Tn).
def pws_constants(t):
    
    if (t < (- 20)):
        raise ValueError('Temperature out of range (-20 - 350°C')
    if (t < 50):
        return (6.116441, 7.591386, 240.7263)
    if (t < 100):
        return (6.004918, 7.337936, 229.3975)
    if (t < 150):
        return (5.856548, 7.27731, 225.1033)
    if (t < 200):
        return (6.002859, 7.290361, 227.1704)
    return (9.980622, 7.388931, 263.1239)