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in Data Science by (50.2k points)

I have a pandas dataframe (df), and I want to do something like:

newdf = df[(df.var1 == 'a') & (df.var2 == NaN)]

I've tried replacing NaN with np.NaN, or 'NaN' or 'nan' etc, but nothing evaluates to True. There's no pd.NaN.

I can use df.fillna(np.nan) before evaluating the above expression but that feels hackish and I wonder if it will interfere with other pandas operations that rely on being able to identify pandas-format NaN's later.

I get the feeling there should be an easy answer to this question, but somehow it has eluded me. Any advice is appreciated. Thank you.

1 Answer

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by (108k points)

When NaN is being compared to itself it returns false. You can use pd.isnull(df.var2) instead of NaN.

If you wish to Learn more about Pandas visit this Pandas Tutorial.

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