熊猫数据框按顺序分组

Question

我有输入数据框：

df1 = pandas.DataFrame( { 
    "Name" : ["Alice", "Bob", "Mallory", "Mallory","Mallory", "Bob" ,"Bob", "Mallory", "Alice"] , 
    "City" : ["Seattle", "Seattle", "Portland", "Seattle", "Seattle", "Portland", "Portland", "Seattle", "Seattle"] } )

我想按名称分组，但不是唯一的，因此输出应为：

["Alice","Bob","Mallory","Bob","Mallory", "Alice"]

我找不到任何有效的方法来做-有没有一种方法可以不遍历所有行？

Answer 1

您可以执行以下操作：

df1.groupby((df1['Name'] != df1['Name'].shift()).cumsum()).first()

收益：

         Name      City
Name                   
1       Alice   Seattle
2         Bob   Seattle
3     Mallory  Portland
4         Bob  Portland
5     Mallory   Seattle
6       Alice   Seattle

如果只需要'Name'列：

df1.groupby((df1['Name'] != df1['Name'].shift()).cumsum())['Name'].first().values

收益：

['Alice' 'Bob' 'Mallory' 'Bob' 'Mallory' 'Alice']