Pandas-跨多个列删除重复项

Question

我正在尝试有效地删除熊猫中的重复项，其中的重复项在两列之间倒转。例如，在此数据帧中：

import pandas as pd
key = pd.DataFrame({'p1':['a','b','a','a','b','d','c'],'p2':['b','a','c','d','c','a','b'],'value':[1,1,2,3,5,3,5]})
df = pd.DataFrame(key,columns=['p1','p2','value'])
print frame

       p1 p2 value
    0  a  b    1
    1  b  a    1
    2  a  c    2
    3  a  d    3
    4  b  c    5
    5  d  a    3
    6  c  b    5

我想删除第1、5和6行，只留下：

      p1 p2 value
    0  a  b    1
    2  a  c    2
    3  a  d    3
    4  b  c    5

提前谢谢你的建议。

Answer 1

对p1和p2值重新排序，使其按规范顺序显示：

mask = df['p1'] < df['p2']
df['first'] = df['p1'].where(mask, df['p2'])
df['second'] = df['p2'].where(mask, df['p1'])

收益率

In [149]: df
Out[149]: 
  p1 p2  value first second
0  a  b      1     a      b
1  b  a      1     a      b
2  a  c      2     a      c
3  a  d      3     a      d
4  b  c      5     b      c
5  d  a      3     a      d
6  c  b      5     b      c

然后可以删除副本：

df = df.drop_duplicates(subset=['value', 'first', 'second'])

---

import pandas as pd
key = pd.DataFrame({'p1':['a','b','a','a','b','d','c'],'p2':['b','a','c','d','c','a','b'],'value':[1,1,2,3,5,3,5]})
df = pd.DataFrame(key,columns=['p1','p2','value'])

mask = df['p1'] < df['p2']
df['first'] = df['p1'].where(mask, df['p2'])
df['second'] = df['p2'].where(mask, df['p1'])
df = df.drop_duplicates(subset=['value', 'first', 'second'])
df = df[['p1', 'p2', 'value']]

收益率

In [151]: df
Out[151]: 
  p1 p2  value
0  a  b      1
2  a  c      2
3  a  d      3
4  b  c      5