如果列中的值在 pandas 中的列表中，则将值写入新列

Question

我正在尝试在 pandas.

中使用列表理解来创建一些复杂的列

例如，我正在尝试使用列表作为参考在 pandas 数据框中创建另一列：

fruit  = ['watermelon', 'apple', 'grape']

string                     new_column
watermelons are cool      watermelon
apples are good           apple
oranges are on sale       NaN

我尝试使用列表理解 -

df['new_column'] = [f in fruit if any(f in s for f in fruit) for s in df['string']]

我认为这不正确，需要一些帮助！

Answer 1

最好使用 str.extract:

fruit  = ['watermelon', 'apple', 'grape']

import re
df['new_column'] = df['string'].str.extract(f"({'|'.join(map(re.escape, fruit))})")

输出：

                 string  new_column
0  watermelons are cool  watermelon
1       apples are good       apple
2   oranges are on sale         NaN

Answer 2

这将完成工作：

import pandas as pd 
import numpy as np
fruit  = ['watermelon', 'apple', 'grape']
df = pd.DataFrame()
df['string'] = ['watermelons are cool', 'apples are good', 'oranges are on sale', 'apples are not watermelons']

output = df['string'].apply(lambda x: ','.join([f for f in fruit if f in x]))
output[output == ''] = np.nan

print(output)

输出：

0          watermelon
1               apple
2                 NaN
3    watermelon,apple
Name: string, dtype: object

如果列中的值在 pandas 中的列表中，则将值写入新列

Write value to new column if value in column is in a list in pandas

pandas

list-comprehension