How To Replace Empty Values In One Column With Modified Values From Another Column?

Suppose I have the following dataframe called mapping_df: mapping | store_id --------|--------- a | 1 b | 2 | 3 c | 4 | 5 I would

Solution 1:

Try this guy:

df['mapping'] = df[['mapping', 'store_id']].apply(lambda x: x[0] if x[0] else 'edit-%d' % x[1], axis=1)

Solution 2:

If the blank entries in the mapping column are NaN rather than just empty strings, the you could use the combine_first() method:

df.mapping = df.mapping.combine_first('edit-' + df.store_id.astype(str))