Pandas:两列的累积计数

第一次创建 MultiIndex Series 通过 DataFrame.stack GroupBy.cumcount ,用于 DataFrame 添加 unstack 具有 add_suffix

print (df)
  winner  loser
0   Dave  Harry
1    Jim   Dave
2   Dave  Steve

s = df.stack()
#if multiple columns in original df
#s = df[['winner','loser']].stack()
df1 = s.groupby(s).cumcount().add(1).unstack().add_suffix('_matches')
print (df1)
   winner_matches  loser_matches
0               1              1
1               1              2
2               3              1

最后附加到原始 数据帧 通过 join :

df = df.join(df1)
print (df)
  winner  loser  winner_matches  loser_matches
0   Dave  Harry               1              1
1    Jim   Dave               1              2
2   Dave  Steve               3              1

flatten ,

 pd.Series(df[['winner','loser']].values.flatten()).value_counts()
 [out]
 Dave     3
 Jim      1
 Harry    1
 Steve    1