Replace NaN values in pandas dataframe with a computation from other columns

Question

I have a DataFrame with column3 containing NaN values. I want to replace these NaN values with column2-column1. But column 2 is a string and I want to take the first four digits from the string and convert it to integer before subracting.

I tried this:

df.column3.fillna(int(df.column2[:4]) - df.column1)

And I get this following error:

TypeError: cannot convert the series to <class 'int'>

jezrael · Accepted Answer · 2021-02-08 06:08:36Z

2

Use str[:4] for first 4 values of strings with convert to numeric by Series.astype:

df.column3 = df.column3.fillna(df.column2.str[:4].astype(int) - df.column1)

Or by to_numeric if first solution failed:

df.column3 = df.column3.fillna(pd.to_numeric(df.column2.str[:4], errors='coerce') - df.column1)

answered Feb 8, 2021 at 6:08

jezrael

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Comments

Mayank Porwal · Accepted Answer · 2021-02-08 06:08:54Z

1

Use:

df.column3.fillna(df.column2.str[:4].astype('int') - df.column1)

answered Feb 8, 2021 at 6:08

Mayank Porwal

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1 Comment

Danush Aaditya Over a year ago

Worked perfectly!

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