python - 根据两列从得分最高的组中选择行

Question

数据

     Sentence  Score_Unigram  Score_Bigram  versionId
0    As of   Dat              5             1  269004158
1     Date Docum              4             3  269004158
2    As of   Dat              4             1  269004158
3     Date Docum              5             3  345973060
4    x Indicate               4             1  372529352
5     Date Docum              5             3  372529352
6   1 Financial               9             1  372529352
7   020 per shar              2             0  372529352
8     Date $ in               8             1  372529352
9     Date $ in               9             4  372529352
10   4 ---------              4             1  372529352
11    Date Begin              1             0  372529352

要求的输出

       Sentence  Score_Unigram  Score_Bigram  versionId
0   As of   Dat              5             1  269004158
3    Date Docum              5             3  345973060
9    Date $ in               9             4  372529352

Objective

按version id分组，得到Score_unigram最大的行，如果结果多于一个，则检查Score_Bigram列，并得到具有最高值的行(如果有多个这样的行则返回所有)

What have I tried

maximum = 0
index_to_pick = []

for index,row_data in a.iterrows():
    if row_data['Score_Unigram'] > maximum:
        maximum = row_data['Score_Unigram']
        score_bigram = row_data['Score_Bigram']
        index_to_pick.append(index)

    elif row_data['Score_Unigram'] == maximum:
        if row_data['Score_Bigram'] > score_bigram:

            maximum = row_data['Score_Unigram']
            score_bigram = row_data['Score_Bigram']
            index_to_pick = []
            index_to_pick.append(index)

        elif row_data['Score_Bigram'] == score_bigram:
            index_to_pick.append(index)

   a.loc[[index_to_pick[0]]]

输出

       Sentence  Score_Unigram  Score_Bigram  versionId
5    Date $ in               9             4  372529352

好吧，我猜这种方法不是很好(因为数据很大)，正在寻找一种有效的方法。我尝试了 idxmax 但它返回了唯一的顶部。可能是重复的，但找不到。感谢您的帮助!

Answer 1

使用 boolean indexing 双重过滤- 首先是第一列 Score_Unigram 的 max，然后是 Score_Bigram:

df = df[ df['Sentence'].duplicated(keep=False)]
df = df[df.groupby('Sentence')['Score_Unigram'].transform('max') == df['Score_Unigram']]
df = df[df.groupby(['Sentence', 'Score_Unigram'])['Score_Bigram'].transform('max') == df['Score_Bigram']]
print (df)
     Sentence  Score_Unigram  Score_Bigram  versionId
0   As of Dat              5             1  269004158
3  Date Docum              5             3  345973060
5  Date Docum              5             3  372529352
9   Date $ in              9             4  372529352