pandasSeries 的索引对象(一)

建一个Series

from pandas import Series,DataFrame obj=Series(range(3),index=['a','b','c']) obj Out[8]: a 0 b 1 c 2 dtype: int32 index=obj.index index Out[10]: Index(['a', 'b', 'c'], dtype='object') index[1:] Out[11]: Index(['b', 'c'], dtype='object')

按照index 重新排序

obj=Series([4.5,7.2,-5.3,3.6],index=['d','b','a','c']) obj Out[25]: d 4.5 b 7.2 a -5.3 c 3.6 dtype: float64 obj2=obj.reindex(['a','b','c','d','e']) obj2 Out[27]: a -5.3 b 7.2 c 3.6 d 4.5 e NaN dtype: float64

ffill 前向排列

obj3=Series(['blue','purple','yellow'],index=[0,2,4]) obj3 Out[29]: 0 blue 2 purple 4 yellow dtype: object obj3.reindex(range(6),method='ffill') Out[30]: 0 blue 1 blue 2 purple 3 purple 4 yellow 5 yellow dtype: object

pad=ffill也是前向排列

obj3.reindex(range(6),method='pad') Out[31]: 0 blue 1 blue 2 purple 3 purple 4 yellow 5 yellow dtype: object

bfill后向排列 =backfill

obj3.reindex(range(6),method='bfill') Out[32]: 0 blue 1 purple 2 purple 3 yellow 4 yellow 5 NaN dtype: object