根据 pandas 中的列进行分组和自动递增 [英] Grouping and auto increment based on columns in pandas

问题描述

我有一个看起来像这样的熊猫框:

i have a pandas frame that looks like this:

有没有一种方法可以在最后一列中添加数字而不必遍历数据框?

Is there a way to add the numbers in the last column without having to iterate through the data frame?

我正在玩结果并分组并自动递增组ID在熊猫中，但出于我的目的而没有使它起作用

I was playing with the results of Grouping and auto incrementing group id in pandas but haven't made it work for my purposes

这是生成数据框的代码

import pandas as pd
columns = ['Product','SubProd', 'NeedThis']
Index=['4/20/2012','4/27/2012','5/4/2012','5/11/2012','5/18/2012','4/20/2012',
'4/27/2012','5/4/2012','5/11/2012','5/18/2012','5/25/2012','10/31/2014','11/7/2014',
'11/14/2014','11/21/2014','11/28/2014']
datas = {'Product' : ['A','A','A','A','A','A','A','A','A','A','A','B','B','B','B','B'],
      'SubProd' : ['BL','BL','BL','BL','BL','lk','lk','lk','lk','lk','lk','po','po','po','po','po']}
df = pd.DataFrame(data=datas, index=Index)

print(df)

谢谢

推荐答案

In [10]: df['counter'] = df.groupby(['Product','SubProd']).cumcount()+1

In [11]: df
Out[11]: 
           Product SubProd  counter
4/20/2012        A      BL        1
4/27/2012        A      BL        2
5/4/2012         A      BL        3
5/11/2012        A      BL        4
5/18/2012        A      BL        5
4/20/2012        A      lk        1
4/27/2012        A      lk        2
5/4/2012         A      lk        3
5/11/2012        A      lk        4
5/18/2012        A      lk        5
5/25/2012        A      lk        6
10/31/2014       B      po        1
11/7/2014        B      po        2
11/14/2014       B      po        3
11/21/2014       B      po        4
11/28/2014       B      po        5

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