How to transpose list elements from multiple columns into rows in pandas DataFrame?

Question

I've got a dataframe like this:

                     args  inputs
0  [a.pl, foo, -bar, baz]  [a, b]
1  [a.pl, BAH, -bar, baz]  [a, c]

There are multiple columns, and all cells contain a list of strings. How can I transpose these lists to produce this:

         args inputs
index i             
0     1  a.pl      a
      2   foo      b
      3  -bar    NaN
      4   baz    NaN
1     1  a.pl      a
      2   BAH      c
      3  -bar    NaN
      4   baz    NaN

Answer 1

Something like stack + unstack

df.stack().apply(pd.Series).stack().unstack(1)
Out[27]: 
     args inputs
0 0  a.pl      a
  1   foo      b
  2  -bar   None
  3   baz   None
1 0  a.pl      a
  1   BAH      c
  2  -bar   None
  3   baz   None