根据条件使用熊猫追加

Question

I have a data frame df1 with columns ID2, Name2, ID3, Name3 . I have other two data frame df2 (columns: Name2, ID2 ) and df3 (columns: Name3, ID3 ) with the same columns. I am trying to merge df2 and df3 based on matching ID, which I do as follows:

Solution = pd.merge(df2,df3, left_on='ID2',right_on='ID3').sort_values('Name2')

Now I want to append this result to df1 , only if ID2/ID3 doesn't already exist in df1 . How do I do that?

Answer 1

使用isin ：

df1.append(Solution[~Solution['ID2'].isin(df1['ID1'])])