将变量值分配给 pandas DataFrame 中的新列

Question

I have created 3 new variables a,b and c using certain conditions. Now I want to assign these variables to a new column in a pandas DataFrame again using some conditions.

I want a code something like what I have written below but in a smarter way. The code below is working fine but it's not a smart solution. Is there a possibility to write a loop, maybe an iterative loop

df2['dest_col'] = np.where(df2['month'] == 'March-2016',a
                  ,(np.where(df2['month'] == 'April-2016',b
                  ,(np.where(df2['month'] == 'May-2016',c)))

Answer 1

You want numpy.select :

cond=[(df2['month'] == month) for month in df2['month'].unique()]
values=[a, b, c] 

df2['dest_col'] = np.select(cond,values)