pandas indexとreindex

dataframe_make

import pandas as pd
import numpy as np
df=pd.DataFrame(np.arange(9).reshape(3,3))

df
# [Out]#    0  1  2
# [Out]# 0  0  1  2
# [Out]# 1  3  4  5
# [Out]# 2  6  7  8

indexはindex振りなおすけど、値は追随。

reindexはindex振りなおすけど、値は追随しないのでNaN

index

df.index=range(100,103)

df
# [Out]#      0  1  2
# [Out]# 100  0  1  2
# [Out]# 101  3  4  5
# [Out]# 102  6  7  8

reindex

df.reindex(range(100,103))
# [Out]#       0   1   2
# [Out]# 100 NaN NaN NaN
# [Out]# 101 NaN NaN NaN
# [Out]# 102 NaN NaN NaN