Thanks Tom.  Will give it a try.

On Monday, November 2, 2020 at 7:44:03 AM UTC-5, Tom Keffer wrote:
>
> A problem is that you're doing arithmetic before checking for a "None" 
> result. For example, 
>
>     ...
>     dp_F = dewpointF(t_F, rh)
>     dp_D = t_F - dp_F
>
>     return dp_D if dp_D is not None else None
>
> If db_F is None, this will fail. Same problem with the other algorithms.
>
> As for adding the results to the database, if you add the types through 
> the xtypes system 
> <https://github.com/weewx/weewx/wiki/WeeWX-V4-user-defined-types>, they 
> will become available throughout WeeWX. Follow the example 
> <https://github.com/weewx/weewx/wiki/WeeWX-V4-user-defined-types#a-comprehensive-example>
>  
> in the Wiki. The biggest challenge will be checking that the units are 
> right.
>
> -tk
>
>
> On Sun, Nov 1, 2020 at 12:58 PM rich T <[email protected] <javascript:>> 
> wrote:
>
>> I want to add Dewpoint Depression and Wetbulb Formulas to the 
>> wxformulas.py file. So far this is what I have 
>>
>> Dewpoint Depression:
>>
>> def dewpointdepressF(t_F, rh):
>>
>>     """Calculate dew point depression. 
>>     
>>     https://www.theweatherprediction.com/habyhints3/904/
>>
>>     t_f: Temperature in Fahrenheit
>>     
>>     rh: relative humidity [0-100]
>>     
>>     Returns: Dewpoint Depression
>>     
>>     """
>>
>>     if t_f is None or rh is None:
>>         return None
>>         
>>     dp_F = dewpointF(t_F, rh)
>>     dp_D = t_F - dp_F
>>
>>     return dp_D if dp_D is not None else None
>>
>> def dewpointdepressC(t_C, rh):
>>
>>     """Calculate dew point depression. 
>>     
>>     https://www.theweatherprediction.com/habyhints3/904/
>>
>>     t_C: temperature in degree Celsius
>>     
>>     rh: relative humidity [0-100]
>>     
>>     Returns: Dewpoint Depression
>>     
>>     """
>>
>>     if t_C is None or rh is None:
>>         return None
>>         
>>     dp_C = dewpointC(t_C, rh)
>>     dp_D = t_C - dp_C
>>
>>     return dp_D if dp_D is not None else None
>>
>> Wetbulb:
>>
>> def wetbulbF(t_F, rh):
>>     
>>     """Estimate the wetbulb temperature (1/3 method). 
>>     
>>     https://theweatherprediction.com/habyhints/170/
>>
>>     t_f: Temperature in Fahrenheit
>>     
>>     rh: relative humidity [0-100]
>>     
>>     dp_DwB: Dewpoint Depression divided by 3
>>     
>>     t_WbF: Wetbulb Temperature in Fahrenheit
>>     
>>     Returns: Wetbulb Temperature Estimation
>>
>>     """
>>
>>     if t_f is None or rh is None:
>>         return None
>>         
>>     dp_F = dewpointF(t_F, rh)
>>     dp_DwB = (t_F - dp_F) / 3
>>     t_WbF = t_F - dp_DwB
>>
>>     return t_WbF if t_WbF is not None else None
>>
>> def wetbulbC(t_C, rh):
>>     
>>     """Estimate the wetbulb temperature (1/3 method). 
>>     
>>     https://theweatherprediction.com/habyhints/170/
>>
>>     t_C: temperature in degree Celsius
>>     
>>     rh: relative humidity [0-100]
>>     
>>     dp_DwB: Dewpoint Depression divided by 3
>>     
>>     t_WbC: Wetbulb Temperature in Celsius
>>     
>>     Returns: Wetbulb Temperature Estimation
>>
>>     """
>>
>>     if t_C is None or rh is None:
>>         return None
>>         
>>     dp_C = dewpointC(t_C, rh)
>>     dp_DwB = (t_C - dp_C) / 3
>>     t_WbC = t_C - dp_DwB
>>
>>     return t_WbC if t_WbC is not None else None
>>
>> Does the coding look okay? I know I need to add two columns to the 
>> database, but what else would need to be updated to get the results in the 
>> database?
>>
>> Rich
>>
>>
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