Consider the dataframe "df" what is the result of the following operation df['symbolling'] = df['symbolling'] + 1?:

The operation df['symbolling'] = df['symbolling'] + 1 will increment the value of each entry in the 'symbolling' column of the dataframe "df" by 1.

Here are the steps:

1. df['symbolling'] selects the 'symbolling' column from the dataframe "df".
2. df['symbolling'] + 1 adds 1 to each entry in the 'symbolling' column.
3. df['symbolling'] = df['symbolling'] + 1 assigns the result back to the 'symbolling' column in the dataframe.

So, if you had a value of 2 in the 'symbolling' column for a particular row, after this operation, the value will be 3. This operation is performed for all rows in the dataframe.