Nested Case when statements in Python

The following code creates as column called ‘Flagged’ in SAS:

Case When t3.Proportion=. then case when t3.'Standardised proportion'n >t1.SigmaMultiple Then 1 else 0  
End
Else 
Case When t3.Proportion=. and  abs(t3.'Standardised proportion'n) > t1.SigmaMultiple Then 1 Else 0
End
End

I'm trying to replicate it in python and usually I would have done a conditions code however the nested Case when aspect is confusing me.

The code i tried but didn't seem to be matching:

conditions =[
     ((dfSigmamissing['Proportion'] == 0) & (dfSigmamissing['SP'] > dfSigmamissing['SigmaMultiple'])),
       ((dfSigmamissing['Proportion'] == 0) & (dfSigmamissing['SP'] < dfSigmamissing['SigmaMultiple'])),
        ((dfSigmamissing['SP'].abs() > (dfSigmamissing['SigmaMultiple'])))
                ]

choices = [1,0,1]

dfSigmamissing['Flagged'] = np.select(conditions, choices, default=0)

Any help would be greatly appreciated.

Thank you