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python - 如何仅将一个数据框中的行添加到某些列中的值不匹配的另一个数据框中

问题描述

我有两个数据框，df1 和 df2（如下所示），我想要 df3。所以基本上，如果重复出现在“完成”列 == 'C' 之间，则从 df1 中删除行，否则保留 df1 行并从 df2 添加剩余行。希望这是有道理的！可能有一种简单的方法可以做到这一点，而我只是让声音比实际更复杂！？

df1:

Complete    Name      Birth
C           Steve     13/07/2000
C           Mike      13/06/2000
C           Sarah     20/05/1936
C           Lewis     14/08/1955
NaN         Martin    15/04/1990
NaN         Lewis     15/04/1990


df2:

Complete    Name      Birth
NaN         Steve     13/07/2000
NaN         Mike      13/06/2000
NaN         Sarah     20/05/1936
NaN         Lewis     14/08/1955
NaN         Martin    15/04/1990
NaN         Lewis     15/04/1990
NaN         Dave      13/04/1935
NaN         Mark      14/07/1932
NaN         Steve     15/06/1970

我希望 df1 因此成为：

Complete    Name      Birth
NaN         Martin    15/04/1990
NaN         Lewis     15/04/1990
NaN         Dave      13/04/1935
NaN         Mark      14/07/1932
NaN         Steve     15/06/1970

标签： pythondataframe

解决方案

# merge both dataframes, 2 tricks, .reset_index()...set_index() will keep the original index and not reset him
# trick 2, use indicator=True which creates the column "_merge" where you can see in which dataframe the rows where found, left, right or both
df = df1.reset_index().merge(df2, on=["Complete", "Name", "Birth"], how="left", indicator=True).set_index("index")
# creates a mask (series with True / False values)
mask = (df["_merge"]=="both") & (df["Complete"] == "C")
# only keep rows where mask == True, the "~" inverts the boolean value, therefore excludes the mask
df = df[~mask]

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