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How to combine two columns

Time:08-11

I have a merged Pandas dataframe in the following format

index value_x value_y
0 nan 3
1 3 nan
2 nan nan
3 -1 1
4 6 nan
5 nan 6
6 -1 nan
7 -1 6
8 nan nan

Since the original dataframes have the value field, therefore value_x and value_y column is gnerated during the merge process. I would like to merge the two columns so the final column would look like:

index value_x value_y value
0 nan 3 3
1 3 nan 3
2 nan nan nan
3 nan 1 1
4 6 nan 6
5 nan 6 6
6 -1 nan -1
7 nan 6 6
8 nan nan nan

In addition, I would like to know if I could avoid the column combining process during the merge process?

Thanks in advance

CodePudding user response:

You can use max

df["value"] = df[["value_x", "value_y"]].max(axis=1)

as this will pick the non-nan value for each row. For this question:

In addition, I would like to know if I could avoid the column combining process during the merge process?

the answer depends on what the two dataframes were before the merge.

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