Apply conditional on two pandas dataframe columns

Question

I have this dataframe:

I want to create a ZIP column which will get the value of ZIP_y when ZIP_x is NaN and the value of ZIP_x when ZIP_x is not NaN.

I tried this code:

dm["ZIP"]=numpy.where(dm["ZIP_x"] is numpy.nan, dm["ZIP_y"],dm["ZIP_x"])

But that gave me this output:

As you can see, the ZIP column seems to be getting the values of ZIP_x in each of its cells.

Do you know how to achieve what I am after?

EdChum · Accepted Answer · 2016-03-01 10:54:25Z

1

You want this:

dm["ZIP"]=numpy.where(dm["ZIP_x"].isnull(), dm["ZIP_y"],dm["ZIP_x"])

You can't use is or == for that matter to compare NaNs

answered Mar 1, 2016 at 10:54

EdChum

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