Convert row names into a column in Pandas

You can do it in one line.

df.rename_axis("newhead").reset_index()

df.index.name = 'newhead'
df.reset_index(inplace=True)

yields

  newhead  head1  head2  head3
0     bar     32      3    100
1     bix     22    NaN    NaN
2     foo     11      1    NaN
3     qux    NaN     10    NaN
4     xoo    NaN      2     20