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最新推荐文章于 2025-06-03 19:16:49 发布

zhangting_123abc

最新推荐文章于 2025-06-03 19:16:49 发布

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文章标签： python numpy 算法

本文链接：https://blog.youkuaiyun.com/zhangting_123abc/article/details/129020173

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1：数据合并之Join

#默认情况下把行索引相同的数据合并到一起。(行合并）

#coding=utf=8
import numpy as np
import pandas as pd
df1=pd.DataFrame(np.ones((2,4)),index=['A','B'],columns=list('abcd'))
#print(df1)
df2=pd.DataFrame(np.zeros((3,3)),index=['A','B','C'],columns=list('xyz'))
#print(df2)
print(df2.join(df1))

2：np.ones( )

一维数组：np.ones(2)

多维数组:np.ones( (2,3) )

3：数据合并之merge

#合并时没有一样的为空

#coding=utf=8
import numpy as np
import pandas as pd
df1=pd.DataFrame(np.ones((2,4)),index=['A','B'],columns=list('abcd'))
#print(df1)
df2=pd.DataFrame(np.zeros((3,3)),index=['A','B','C'],columns=list('xyz'))
#print(df2)
#print(df2.join(df1))

df3=pd.DataFrame(np.zeros((3,3)),columns=list('fax'))
#print(df3)
print(df1.merge(df3,on='a'))

#并连接

#coding=utf=8
import numpy as np
import pandas as pd
df1=pd.DataFrame(np.ones((2,4)),index=['A','B'],columns=list('abcd'))
df1.loc['A','a']=100
print(df1)
print('*'*100)
df2=pd.DataFrame(np.zeros((3,3)),index=['A','B','C'],columns=list('xyz'))
#print(df2)
#print(df2.join(df1))

df3=pd.DataFrame(np.arange(9).reshape((3,3)),columns=list('fax'))
print(df3)
print('*'*100)
print(df1.merge(df3,on='a'))

#coding=utf=8
import numpy as np
import pandas as pd
df1=pd.DataFrame(np.ones((2,4)),index=['A','B'],columns=list('abcd'))
df1.loc['A','a']=100
print(df1)
print('*'*100)
df2=pd.DataFrame(np.zeros((3,3)),index=['A','B','C'],columns=list('xyz'))
#print(df2)
#print(df2.join(df1))

df3=pd.DataFrame(np.arange(9).reshape((3,3)),columns=list('fax'))
print(df3)
print('*'*100)
print(df1.merge(df3,on='a'))
print('*'*100)
print(df1.merge(df3,on='a',how='inner'))
print('*'*100)
print(df1.merge(df3,on='a',how='outer'))
print('*'*100)
print(df1.merge(df3,on='a',how='left'))
print('*'*100)
print(df1.merge(df3,on='a',how='right'))
print(df1.merge(df3,left_on='b',right_on='x',how='left'))

4：df2.loc[1,a]=1

#第1行的a列赋值为1