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

Convert that column into a DataFrame with .apply(pd.Series). If you stack the columns, you can call the unique method on the returned Series.

df
Out[123]: 
            val
0      [v1, v2]
1      [v3, v2]
2  [v4, v3, v2]

---

df['val'].apply(pd.Series).stack().unique()
Out[124]: array(['v1', 'v2', 'v3', 'v4'], dtype=object)