pandas dropna-存储丢弃的行 [英] Pandas dropna - store dropped rows

问题描述

我正在使用 pandas. DataFrame.dropna 方法删除包含NaN的行.该函数返回一个数据帧，该数据帧不包含被删除的行，如文档所示.

I am using the pandas.DataFrame.dropna method to drop rows that contain NaN. This function returns a dataframe that excludes the dropped rows, as shown in the documentation.

如何将删除的行的副本存储为单独的数据框?是:

How can I store a copy of the dropped rows as a separate dataframe? Is:

mydataframe[pd.isnull(['list', 'of', 'columns'])]

始终确保返回dropna删除的相同行，假设dropna是用subset=['list', 'of', 'columns']调用的?

always guaranteed to return the same rows that dropna drops, assuming that dropna is called with subset=['list', 'of', 'columns'] ?

推荐答案

您可以通过使用

You can do this by indexing the original DataFrame by using the unary ~ (invert) operator to give the inverse of the NA free DataFrame.

na_free = df.dropna()
only_na = df[~df.index.isin(na_free.index)]

另一种选择是使用 ufunc ~ .

Another option would be to use the ufunc implementation of ~.

only_na = df[np.invert(df.index.isin(na_free.index))]

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