Split String in Pandas Series

Can I use the split() function to transfer this series:

s = pd.Series(['adh', 'bei', np.nan, 'cfj'])

To either one of those outputs:

s = pd.DataFrame({
    'A': ['a', 'b', 'c'],
    'B': ['d', 'e', 'f'],
    'C': ['h', 'i', 'j']
})

or:

s = pd.DataFrame({
    'A': ['a', 'b', np.nan, 'c'],
    'B': ['d', 'e', np.nan, 'f'],
    'C': ['h', 'i', np.nan, 'j']
})

You can str.split with a regex matching a character before and after the split point:

s.str.split('(?<=.)(?=.)', expand=True)

Output:

     0    1    2
0    a    d    h
1    b    e    i
2  NaN  NaN  NaN
3    c    f    j

To avoid the NaNs, add a dropna:

s.dropna().str.split('(?<=.)(?=.)', expand=True)

Output:

   0  1  2
0  a  d  h
1  b  e  i
3  c  f  j

Regex

regex demo

(?<=.)  # match a character before
        # match empty string
(?=.)   # match a character after

Alternatively, you could also convert each string to list and pass to the DataFrame constructor:

out = pd.DataFrame(map(list, s.dropna()))