Cannot change the None values in an SFrame using apply()

Question

I am using this code to change the None values in the SFrame:

sarr['value'] = sarr['value'].apply(lambda x: '-1' if x is None else x)

After running this code, I still see the same None values, no effect. Any ideas what is going on here?

Answer 1

The following method of SFrame worked:

sarr = sarr.fillna('value', -1)