pandas mesclar certas colunas
df = pd.merge(df,df2[['Key_Column','Target_Column']],on='Key_Column', how='left')
Rich Ray
df = pd.merge(df,df2[['Key_Column','Target_Column']],on='Key_Column', how='left')
pd.merge(frame_1, frame_2, left_on='county_ID', right_on='countyid')
df['A'] = df[a_cols].apply(' '.join, axis=1)