Python 自定义权重

根据以下详细信息，dataframe具有公司级编号。Dict有自定义权重。公司“A”有7行，所以我想从dict获取自定义权重，键为7，并创建“自定义权重”作为新列。最新日期将具有最高权重

类似地，对于公司“B”和“C”，我需要分别获取和附加键为4和2的权重（每个公司的行数）。将这些权重对齐到“自定义权重”列中

请建议如何解决这个问题？先谢谢你

df=pd.DataFrame(columns=['CompanyName','Date_Published','Stand_Alone','Consolidated'],data=[('A','31-03-2017',np.random.rand(),np.random.rand()),('A','31-03-2016',np.random.rand(),np.random.rand()),('A','31-03-2015',np.random.rand(),np.random.rand()),('A','31-03-2014',np.random.rand(),np.random.rand()),('A','31-03-2013',np.random.rand(),np.random.rand()),('A','31-03-2012',np.random.rand(),np.random.rand()),('A','31-03-2011',np.random.rand(),np.random.rand()),('B','31-03-2017',np.random.rand(),np.random.rand()),('B','31-03-2016',np.random.rand(),np.random.rand()),('B','31-03-2015',np.random.rand(),np.random.rand()),('B','31-03-2014',np.random.rand(),np.random.rand()),('C','31-03-2017',np.random.rand(),np.random.rand()),('C','31-03-2016',np.random.rand(),np.random.rand())])

dict_wt.update({2:[55.55,44.45]})
dict_wt.update({3:[47.34,31,56,21,11]})
dict_wt.update({7:[21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]})

---

如果我正确理解您的问题，这可能是一个解决方案：

import pandas as pd, numpy as np

df=pd.DataFrame(columns=['CompanyName','Date_Published','Stand_Alone','Consolidated'],data=[('A','31-03-2017',np.random.rand(),np.random.rand()),('A','31-03-2016',np.random.rand(),np.random.rand()),('A','31-03-2015',np.random.rand(),np.random.rand()),('A','31-03-2014',np.random.rand(),np.random.rand()),('A','31-03-2013',np.random.rand(),np.random.rand()),('A','31-03-2012',np.random.rand(),np.random.rand()),('A','31-03-2011',np.random.rand(),np.random.rand()),('B','31-03-2017',np.random.rand(),np.random.rand()),('B','31-03-2016',np.random.rand(),np.random.rand()),('B','31-03-2015',np.random.rand(),np.random.rand()),('B','31-03-2014',np.random.rand(),np.random.rand()),('C','31-03-2017',np.random.rand(),np.random.rand()),('C','31-03-2016',np.random.rand(),np.random.rand())])

dict_wt = {}
dict_wt.update({2:[55.55,44.45]})
dict_wt.update({4:[11,56,21,11]})
dict_wt.update({7:[21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]})

weights = df['CompanyName'].value_counts().map(dict_wt)
df['CustomWeights'] = df['CompanyName'].map(weights)

#    CompanyName Date_Published  Stand_Alone  Consolidated  \
# 0            A     31-03-2017     0.465561      0.449511   
# 1            A     31-03-2016     0.096015      0.472931   
# 2            A     31-03-2015     0.176293      0.520192   
# 3            A     31-03-2014     0.814840      0.043019   
# 4            A     31-03-2013     0.387406      0.709103   
# 5            A     31-03-2012     0.790282      0.751466   
# 6            A     31-03-2011     0.047402      0.788732   
# 7            B     31-03-2017     0.275830      0.214845   
# 8            B     31-03-2016     0.341561      0.861411   
# 9            B     31-03-2015     0.800487      0.469386   
# 10           B     31-03-2014     0.071154      0.454278   
# 11           C     31-03-2017     0.712978      0.034975   
# 12           C     31-03-2016     0.672991      0.158985   

#                                        CustomWeights  
# 0   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 1   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 2   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 3   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 4   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 5   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 6   [21.63, 18.54, 15.89, 13.62, 11.68, 10.01, 8.63]  
# 7                                   [11, 56, 21, 11]  
# 8                                   [11, 56, 21, 11]  
# 9                                   [11, 56, 21, 11]  
# 10                                  [11, 56, 21, 11]  
# 11                                    [55.55, 44.45]  
# 12                                    [55.55, 44.45]  

使用

groupby（）

你的目标输出是什么样子的？这真是优雅而精彩！！顺便说一句，dict_wt.update（{3:[47.34,31,56,21,11]}）应更改为dict_wt.update（{4:[47.34,31,56,21]}），以更正我的查询中的打字错误。谢谢jpp！我相信您的解决方案对于解决即将到来的技术挑战会很方便。
df['CustomWeights'] = df.groupby('CompanyName')['Date_Published'].transform(lambda x: dict_wt.get(len(x)))

 CompanyName Date_Published  Stand_Alone  Consolidated  CustomWeights
0            A     31-03-2017     0.116712      0.044908          21.63
1            A     31-03-2016     0.228525      0.553351          18.54
2            A     31-03-2015     0.476527      0.913417          15.89
3            A     31-03-2014     0.989796      0.716775          13.62
4            A     31-03-2013     0.702358      0.880009          11.68
5            A     31-03-2012     0.531666      0.013267          10.01
6            A     31-03-2011     0.896103      0.351544           8.63
7            B     31-03-2017     0.405370      0.701944          11.00
8            B     31-03-2016     0.858221      0.450118          56.00
9            B     31-03-2015     0.163273      0.613447          21.00
10           B     31-03-2014     0.635888      0.570327          11.00
11           C     31-03-2017     0.680992      0.488191          55.55
12           C     31-03-2016     0.083883      0.682186          44.45