我有 Dataframe df_student

Name  Age           City    Stream  Percentage
0    Noah   22      London_UK      Math          90
1  Oliver   20  Birmingham_UK  Commerce          90
2  George   21     Glasgow_UK   Science          96
3  Arthur   19   Liverpool_UK      Math          75
4   Oscar   18     Bristol_UK      Math          70
5     Leo   22  Manchester_UK   Science          80

我想用'_'拆分**df_student ['City']**列，并且只更新同一列中的城市名称。
生成df_student Dataframe 应如下所示

Name  Age           City    Stream  Percentage
0    Noah   22         London      Math          90
1  Oliver   20     Birmingham  Commerce          90
2  George   21        Glasgow   Science          96
3  Arthur   19      Liverpool      Math          75
4   Oscar   18        Bristol      Math          70
5     Leo   22     Manchester   Science          80

我怎样才能做到这一点？