有没有办法将 f 字符串合并到 pandas loc 输出中答案

【问题标题】：Is there a way to incorporate f strings in pandas loc output有没有办法将 f 字符串合并到 pandas loc 输出中
【发布时间】：2021-07-25 15:32:17
【问题描述】：

我正在尝试设置一个脚本，该脚本将为学生报告生成 cmets。为了设置一个通用模板，我使用了一个包含百分比分数的分数表。我无法使用 f 字符串插入每个学生的姓名，以及任何相关的代词或教学科目。

目前，我已经写了这个：

report = pd.DataFrame({'Preferred Name': ['Jack', 'Jenny', 'Bob'],
                       'Topic': ['English', 'English', 'Maths'],
                       'HomeworkAv': [84.6, 68, 94.1]})
name = report['Preferred Name']
topic = report['Topic']
report.loc[report['HomeworkAv'] >= 80, 'TopicSentence'] = f"{name} has consistently demonstrated an excellent understanding for {topic} throughout the entire term. "

问题在于，每次在 f 字符串中插入一个变量，它都会列出该变量中的每个值。我可以看到明确的问题是什么，但我不知道如何解决它。

有没有办法可以做到这一点？

【问题讨论】：

标签： python pandas dataframe f-string pandas-loc

【解决方案1】：

您可以使用apply 语句完成它。

我将这样做：

import pandas as pd
report = pd.DataFrame({'Preferred Name': ['Jack', 'Jenny', 'Bob'],
                       'Topic': ['English', 'English', 'Maths'],
                       'HomeworkAv': [84.6, 68, 94.1]})

report['TopicSentence'] = report.apply(lambda x: f"{x['Preferred Name']} has consistently demonstrated an excellent understanding for {x['Topic']} throughout the entire term." if x['HomeworkAv'] >= 80 else None, axis=1)
                                
print (report)

或者你也可以这样做：

notes = "{} has consistently demonstrated an excellent understanding for {} throughout the entire term."
report['TopicSentence'] = report.apply(lambda x: notes.format(x['Preferred Name'],x['Topic']) if x['HomeworkAv'] >= 80 else None, axis=1)

输出将是：

  Preferred Name  ...                                                                              TopicSentence
0           Jack  ...  Jack has consistently demonstrated an excellent understanding for English throughout t...
1          Jenny  ...                                                                                       None
2            Bob  ...  Bob has consistently demonstrated an excellent understanding for Maths throughout the ...

【讨论】：

【解决方案2】：

如果你想用.loc()方法和f-string一起实现任务，你可以这样做：

report.['TopicSentence'] = ''     # initialize the sentence to ''
report.loc[report['HomeworkAv'] >= 80, 'TopicSentence'] = report.loc[report['HomeworkAv'] >= 80].apply(lambda x: f"{x['Preferred Name']} has consistently demonstrated an excellent understanding for {x['Topic']} throughout the entire term. ", axis=1)


print(report)

  Preferred Name    Topic  HomeworkAv                                                                                           TopicSentence
0           Jack  English        84.6  Jack has consistently demonstrated an excellent understanding for English throughout the entire term. 
1          Jenny  English        68.0                                                                                                        
2            Bob    Maths        94.1     Bob has consistently demonstrated an excellent understanding for Maths throughout the entire term.

【讨论】：

【解决方案3】：

使用numpy它是fast：

import numpy as np
report['HomeworkAv'] = np.where(report['HomeworkAv'] >= 80 , report['Preferred Name'] +  'has consistently demonstrated an excellent understanding for' + report['Topic'] + 'throughout the entire term', '')

注意：如果您有多个条件，请使用np.select

【讨论】：