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 pd
import numpy as np

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

b.sort_index()

b.sort_index(ascending=False)

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

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

.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()

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

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

# 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()

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

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

c = a + b
c

c.sort_values(2,ascending = False)

c.sort_values(2,ascending = True)