在python中使用Pandas合并后如何查找删除的数据? [英] How to find dropped data after using Pandas merge in python?

问题描述

我的数据框如下所示:我正在使用Pandas合并功能来合并两个数据框，并且试图找到被删除的行.在Pandas或python中有没有办法跟踪此信息?

My Dataframe looks like following.I am using Pandas merge function to merge two dataframes, and I am trying to find row that was dropped. Is there a way in Pandas or python to track this ?

df1=pd.DataFrame(({'Name':('A','B','C'),'Age':(34,23,90)}))
df2=pd.DataFrame(({'Name':('A','B','D'),'Add':('rt','ct','pt')}))
pd.merge(df1,df2,on='Name')

推荐答案

使用通过 boolean indexing :

Last filter no both rows by boolean indexing:

print (df[df['_merge'] != 'both'])
  Name   Age  Add      _merge
2    C  90.0  NaN   left_only
3    D   NaN   pt  right_only

另一种解决方案是使用 isin 并按~反转掩码:

Another solution is filtering with isin and inverting mask by ~:

print (df1[~df1['Name'].isin(df2['Name'])])
  Name  Age
2    C   90

print (df2[~df2['Name'].isin(df1['Name'])])
  Name Add
2    D  pt

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