Create dictionary from results of DataFrame in pandas

Question

I have a dataframe with results as below. Sample dataframe shown actual one is much larger. I want to get a dictionary (or another structure if it will be faster) with the

Answer 1

df.stack().reset_index(level=1).groupby(level=0).level_1.apply(list).to_dict()
Out[764]: {1: ['MSFT'], 2: ['GOOG', 'AMZN'], 3: ['AAPL', 'AMZN', 'FB'], 4: ['FB']}