[Python] FutureWarning: A value is trying to be set on a copy of a DataFrame or Series through...

I'm encountering a FutureWarning when trying to fill missing values in the "age" column of my DataFrame with the mean of the column. The warning suggests that the behavior will change in Pandas 3.0, and the inplace method will not work as expected due to the intermediate object always behaving as a copy.

Here is the warning message I receive

FutureWarning: A value is trying to be set on a copy of a DataFrame or Series through chained assignment using an inplace method.


The behavior will change in pandas 3.0. This inplace method will never work because the intermediate object on which we are setting values always behaves as a copy.

I understand that this issue arises from using the inplace parameter with chained assignment. Here’s the code that triggers the warning

df['age'].fillna(df['age'].mean(), inplace=True)


I need an alternative approach that updates the DataFrame without using inplace=True and avoids the warning. I tried the following methods, but they didn’t change the DataFrame as expected

1. Reassigning the result back to the column

df['age'] = df['age'].fillna(df['age'].mean())

1. Using a dictionary with fillna

df.fillna({'age': df['age'].mean()}, inplace=True)


Despite these attempts, the DataFrame still shows 891 missing values in the "age" column after trying to fill them.

Continue reading...