pandas merge columns in same dataframe
<p>I have dataframe with 4 columns. </p>

<pre><code>    Column1    Column2    Column3    Column4
0   Item1      Value1     Item2      Value2
1   Item3      Value3     Item4      Value4
2   Item5      Value5     Item6      Value6
3   Item7      Value7     Item8      Value8
4   Item9      Value9     Item10     Value10
5   Item11     Value11    Item12     Value12
6   Item13     Value13    Item14     Value14
</code></pre>

<p>Is there a way for me to combine <code>Column1</code> and <code>Column3</code> together? and with <code>Column2</code> and <code>Column4</code>? To get the below</p>

<pre><code>    Column1    Column2
0   Item1      Value1
1   Item2      Value2
2   Item3      Value3
3   Item4      Value4
4   Item5      Value5
5   Item6      Value6
6   Item7      Value7
7   ...
</code></pre>

<p>I've tried playing with <code>append</code>, <code>concat</code> and <code>split</code> but cant seem to work it out.. </p>

<pre><code>df.columns = pd.MultiIndex.from_product(
    [['One', 'Two'], ['Column1', 'Column2']])
df.stack(0).reset_index(drop=True)
</code></pre>

<p><a href="http://i.stack.imgur.com/Eb8GR.png" rel="nofollow"><img src="http://i.stack.imgur.com/Eb8GR.png" alt="enter image description here"></a></p>

python pandas