Pandas数据排序

.sort_index() 在指定轴上根据索引进行排序，索引排序后内容会跟随排序

import pandas as pdimport numpy as npb = pd.DataFrame(np.arange(20).reshape(4,5),index=['c','a','d','b'])b

0 1 2 3 4 c 0 1 2 3 4 a 5 6 7 8 9 d 10 11 12 13 14 b 15 16 17 18 19

b.sort_index()

0 1 2 3 4 a 5 6 7 8 9 b 15 16 17 18 19 c 0 1 2 3 4 d 10 11 12 13 14

b.sort_index(ascending=False)

0 1 2 3 4 d 10 11 12 13 14 c 0 1 2 3 4 b 15 16 17 18 19 a 5 6 7 8 9

b.sort_index(axis=0, ascending=False) # 按行标排序，ascending：False为降序

0 1 2 3 4 d 10 11 12 13 14 c 0 1 2 3 4 b 15 16 17 18 19 a 5 6 7 8 9

b.sort_index(axis=1, ascending=False) # 按列标排序

4 3 2 1 0 c 4 3 2 1 0 a 9 8 7 6 5 d 14 13 12 11 10 b 19 18 17 16 15

.sort_values() 在指定轴上根据数值进行排序，默认升序

• Series.sort_values(axis=0,ascending=True)
• DataFrame.sort_values(by,axis=0,ascending=True)
  
  • by：axis轴上的某个索引或索引列表

dates = pd.date_range('20130101', periods=10)dates

DatetimeIndex(['2013-01-01', '2013-01-02', '2013-01-03', '2013-01-04',               '2013-01-05', '2013-01-06', '2013-01-07', '2013-01-08',               '2013-01-09', '2013-01-10'],              dtype='datetime64[ns]', freq='D')

df = pd.DataFrame(np.random.randn(10,4),index=dates,columns=['A','B','C','D'])df.head()

A B C D 2013-01-01 -0.300266 0.683232 0.777509 -0.274338 2013-01-02 2.298084 -0.855524 1.462064 -0.725142 2013-01-03 0.512711 0.824380 0.384902 -1.437241 2013-01-04 0.388478 -1.265414 -1.104333 -0.447689 2013-01-05 0.273518 -0.314857 -2.545510 -1.301629

c = df.sort_values('B')c.head()

A B C D 2013-01-01 -0.976353 -2.176075 0.255585 0.645465 2013-01-03 -1.549727 -1.876790 0.966724 0.486101 2013-01-06 -0.000467 -1.430820 -1.803610 -0.587985 2013-01-10 -0.293663 -0.691951 0.262666 -1.298977 2013-01-04 -0.032301 -0.618582 1.204373 -0.302137

c = df.sort_values('B',ascending = False)c.head()

A B C D 2013-01-03 0.512711 0.824380 0.384902 -1.437241 2013-01-01 -0.300266 0.683232 0.777509 -0.274338 2013-01-08 0.010939 0.591777 0.143182 0.461798 2013-01-10 0.811169 0.100516 -1.385373 0.168329 2013-01-05 0.273518 -0.314857 -2.545510 -1.301629

# 指定1轴排序,这里指定1轴a行为基准排序c = df.sort_values('2013-01-01',axis=1,ascending=False) c.head()

C B D A 2013-01-01 0.777509 0.683232 -0.274338 -0.300266 2013-01-02 1.462064 -0.855524 -0.725142 2.298084 2013-01-03 0.384902 0.824380 -1.437241 0.512711 2013-01-04 -1.104333 -1.265414 -0.447689 0.388478 2013-01-05 -2.545510 -0.314857 -1.301629 0.273518

---

NaN空值统一放在排序末尾

a = pd.DataFrame(np.arange(12).reshape(3,4),index=['a','b','c'])a

0 1 2 3 a 0 1 2 3 b 4 5 6 7 c 8 9 10 11

b = pd.DataFrame(np.arange(20).reshape(4,5),index=['c','a','d','b'])b

0 1 2 3 4 c 0 1 2 3 4 a 5 6 7 8 9 d 10 11 12 13 14 b 15 16 17 18 19

c = a + bc

0 1 2 3 4 a 5.0 7.0 9.0 11.0 NaN b 19.0 21.0 23.0 25.0 NaN c 8.0 10.0 12.0 14.0 NaN d NaN NaN NaN NaN NaN

c.sort_values(2,ascending = False)

0 1 2 3 4 b 19.0 21.0 23.0 25.0 NaN c 8.0 10.0 12.0 14.0 NaN a 5.0 7.0 9.0 11.0 NaN d NaN NaN NaN NaN NaN

c.sort_values(2,ascending = True)

0 1 2 3 4 a 5.0 7.0 9.0 11.0 NaN c 8.0 10.0 12.0 14.0 NaN b 19.0 21.0 23.0 25.0 NaN d NaN NaN NaN NaN NaN