how to apply fillna for all columns in pandas code example

Example 1: fillna with mean pandas

sub2['income'].fillna((sub2['income'].mean()), inplace=True)

Example 2: fillna pandas inplace

When inplace = True , the data is modified in place, which means it will return nothing and the dataframe is now updated. When inplace = False , which is the default, then the operation is performed and it returns a copy of the object. You then need to save it to something.