How to compile all lists in a column into one unique list

Question

I have a pandas dataframe as below:

How can I combine all the lists (in the \'val\' column) into a unique list (set), e.g. [val1, val2, val33, val9, v

Answer 1

One way would be to extract those elements into an array using np.hstack and then using np.unique to give us an array of such unique elements, like so -

np.unique(np.hstack(df.val))

If you want a list as output, append with .tolist() -

np.unique(np.hstack(df.val)).tolist()