pandas series and datarame align操作

最新推荐文章于 2025-05-28 00:15:00 发布

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最新推荐文章于 2025-05-28 00:15:00 发布

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本文深入探讨了Pandas库中Series和DataFrame的对齐操作，包括不同join参数的使用，如'outer', 'inner', 'left', 'right'，展示了如何通过align()方法处理不匹配的索引，是理解Pandas数据操作的重要资源。

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import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

'''The align() method is the fastest way to simultaneously align two objects. It supports a join argument 
(related to joining and merging):

join='outer': take the union of the indexes (default)
join='left': use the calling object’s index
join='right': use the passed object’s index
join='inner': intersect the indexes
It returns a tuple with both of the reindexed Series:'''


#Series操作
s=pd.Series(np.random.randn(5),index=list('abcde'))
s1=s[:4]
s2=s[1:]
# print(s1)
# print(s2)
tt=s1.align(s2)
# print(type(s1.align(s2))) #<class 'tuple'>
# print(list(tt)[0])
# print(type(list(tt)[0]))  #<class 'pandas.core.series.Series'>
# print(s1.align(s2, join='inner'))
# print('*'*44)
# print(s1.align(s2, join='left'))
# print('*'*44)
# print(s1.align(s2, join='right'))
# print('*'*44)

'''For DataFrames, the join method will be applied to both the index and the columns by default:'''

df=pd.DataFrame({
    'one':pd.Series(np.random.randn(3),index=list('abc')),
    'two':pd.Series(np.random.randn(4),index=list('abcd')),
    'three':pd.Series(np.random.randn(3),index=list('bcd'))
},columns=['one','two','three'])

df2=pd.DataFrame({
    'one':pd.Series(np.random.randn(3),index=list('abc')),
    'two':pd.Series(np.random.randn(3),index=list('abc'))
})
print(list(df.align(df2))[1])
print('*'*44)
'''        one  three       two
a  1.157157    NaN  0.445614
b -0.299403    NaN  0.262753
c -0.537562    NaN  0.127325
d       NaN    NaN       NaN'''

print(df.align(df2,join='right'))
'''(        one       two
a  0.608164 -1.179006
b  1.169596  2.313169
c  1.044233  0.481608,         one       two
a -0.965940 -1.640197
b  1.185849 -0.166843
c  1.409709  0.497200)
'''