如果其他两个列在Pandas中具有匹配的值，如何用另一个数据框的值填充空列的值？

Question

I have two similar dataframes. I want to populate df2['Material'] with the value from df1['Material'] if df1['PartNumber'] and df2['PartNumber'] match. Do can I accomplish this with Pandas (or Python in general)? The data frames are several thousand lines each, these are just snippets.

df1
    PartNumber      Material    ProgramNo   Machine

114 JEFD0302000 E   304L        O0219       CHNC III
218 REFD0502050 B   6AL-4V      O0295       CHNC III

df2
    PartNumber      ProgramNo     Machine   Material

0   JEFD0302670 A   6109 + 6609   WY-100    NaN
1   JEFD0510820 A   6110 + 6610   WY-100    NaN

Answer 1

你可以做 ：

df2['Material']=df2['PartNumber'].map(dict(zip(df1['PartNumber'],df1['Material']))).fillna(df2.Material)

Answer 2

Using np.where with map

s=df2.PartNumber.map(df1.set_index('PartNumber').Material)    
df2.Material=np.where(df2.PartNumber.isnull(),s,df2.Material)