Use numpy exp() in tsat()

Author: acroucher

t2thermo.py

@@ -258,6 +258,7 @@ def sat(t, bounds = False):
     """Saturation pressure (Pa) as a function of temperature (deg C).
     If bounds is True, returns None if the temperature is out of 
     range."""
+    import numpy as np
     a = [0., -7.691234564, -2.608023696e1, -1.681706546e2, 6.423285504e1,
        -1.189646225e2, 4.167117320, 2.097506760e1, 1.0e9, 6.0]
     if bounds:
@@ -275,7 +276,7 @@ def sat(t, bounds = False):
             SC = SC * X1
             d1 = 1.0 + a[6] * X1 + a[7] * X2
             d2 = a[8] * X2 + a[9]
-            PC = exp(SC / (TC * d1) - X1 / d2)
+            PC = np.exp(SC / (TC * d1) - X1 / d2)
             return PC * 2.212e7
         else: return None
     else: return None