基于行的某个值派生一个新列并应用，直到下一个值再次出现

Question

在dataframe string列中，我希望基于行的值派生一个新列，直到下一个值再次出现。最有效的方法是什么/最干净的方法是什么？你知道吗

输入数据帧：

import pandas as pd

df = pd.DataFrame({'neighborhood':['Chicago City', 'Wicker Park', 'Bucktown','Lincoln Park','West Loop','River North','Milwaukee City','Bay View','East Side','South Side','Bronzeville','North Side','New York City','Harlem','Midtown','Chinatown']})

我想要的数据帧输出是：

      neighborhood city
0     Chicago City Chicago
1      Wicker Park Chicago
2         Bucktown Chicago
3     Lincoln Park Chicago
4        West Loop Chicago
5      River North Chicago
6   Milwaukee City Milwaukee
7         Bay View Milwaukee
8        East Side Milwaukee
9       South Side Milwaukee
10     Bronzeville Milwaukee
11      North Side Milwaukee
12   New York City New York
13          Harlem New York
14         Midtown New York
15       Chinatown New York

Answer 1

使用.str.extract+ffill

df['city'] = df.neighborhood.str.extract('(.*)\sCity').ffill()