如何将此代码重写为 apply-lambda 表达式？答案

【问题标题】：How to rewrite this code into an apply-lambda expression?如何将此代码重写为 apply-lambda 表达式？
【发布时间】：2020-12-14 09:40:25
【问题描述】：

我的数据框（df）在新列“s_score”中有一些 NaN 条目，我可以使用 func(x) 将其排除。即 document_path_similarity() 的执行会导致一些 NaN，从而阻止 most_similar_docs() 的执行（如果我不首先使用 func(x) ）。 D1,D2 是带有字符串数据的 df.columns。

df
Quality D1                                  D2
0   1   Ms Stewart, the chief executive...  Ms Stewart, 61, its chief executive 
1   1   After more than two years' det...   After more than two years in

def most_similar_docs():

    def func(x):
        try:
            return document_path_similarity(x['D1'], x['D2'])
        except:
            return np.nan
    df['s_score'] = df.apply(func, axis=1)

有没有办法将此代码重写为单行代码？

我的以下尝试导致'ValueError: ('max() arg is an empty sequence' 或 SyntaxError。

df['s_scores'] = df.apply(lambda x: document_path_similarity(x.D1, x.D2),axis=1)
paraphrases['s_scores'] = paraphrases.apply(lambda x: document_path_similarity(x.D1, x.D2),axis=1 if np.isnan(x))

【问题讨论】：

document_path_similarity 的导入/pip 安装是什么？

标签： pandas lambda python-3.6 apply nan

【解决方案1】：

我认为您的pandas 代码没有任何问题。我确实发现similarity_score() 失败了，因为它试图获取最大的空列表。我通过强制输入零分来强制列表为非空。这是我第一次查看这个库，所以请不要认为我的补丁质量很好。

import io
df = pd.read_csv(io.StringIO("""  Quality  D1                                  D2
0   1   Ms Stewart, the chief executive...  Ms Stewart, 61, its chief executive 
1   1   After more than two years' det...   After more than two years in """), sep="\s\s+", engine="python")

def similarity_score(s1, s2):
    list1 = []
    for a in s1:
        # patch +[0] at end so never finding max of empty list
        list1.append(max([i.path_similarity(a) for i in s2 if i.path_similarity(a) is not None]+[0]))
    output = sum(list1)/len(list1)
    return output

df = df.assign(
    s_scores=lambda x: x.apply(lambda r: document_path_similarity(r.D1, r.D2), axis=1)
)

print(df.to_string(index=False))

输出

 Quality                                  D1                                   D2  s_scores
       1  Ms Stewart, the chief executive...  Ms Stewart, 61, its chief executive  0.838889
       1   After more than two years' det...         After more than two years in  0.912500

【讨论】：