Convert Pandas DataFrame into 2 columns

Question

I have a Pandas DataFrame like so:

  | A | B | C |
0 | 3 | e | w |
1 | 4 | f | x |
2 | 5 | g | y |
3 | 6 | h | z |

I'm trying to convert the DataFrame into a two-column structure that preserves the index value, like so:

0 | 3 |
0 | e |
0 | w |
1 | 4 |
1 | f |
1 | x |
2 | 5 |
2 | g |
2 | y |
3 | 6 |
3 | h |
3 | z |

I've tried using df.melt but it doesn't seem to do what I need. Thanks in advance for any help.

Answer 1

You can use stack:

df.stack().reset_index(level=1,drop=True) # df.stack().droplevel(1)

0    3
0    e
0    w
1    4
1    f
1    x
2    5
2    g
2    y
3    6
3    h
3    z

Answer 2

Yes you can use melt with sort_index:

>>> df.melt(ignore_index=False).sort_index()['value']
0    3
0    e
0    w
1    4
1    f
1    x
2    5
2    g
2    y
3    6
3    h
3    z
Name: value, dtype: object

Or with stack:

>>> df.stack().droplevel(1)
0    3
0    e
0    w
1    4
1    f
1    x
2    5
2    g
2    y
3    6
3    h
3    z
dtype: object