如何在 pandas 的一列中转换多列？

Question

I have the following dataframe:

   route1  route2
1    19.0    51.0
2    47.0    46.0
3    56.0    37.0
4    43.0     2.0

I would like to have the following output.

     edge    route
1    19.0   route1
2    47.0   route1
3    56.0   route1
4    43.0   route1
5    51.0   route2
6    46.0   route2
7    37.0   route2
8     2.0   route2

How can I do that? I checked that Pandas: Multiple columns into one column but it doesnt help that much with the new column routes that I want to create.

Thank you in advance!

Answer 1

Use melt :

>>> df.melt(var_name='route', value_name='edge')
    route   edge
0  route1   19.0
1  route1   47.0
2  route1   56.0
3  route1   43.0
4  route2   51.0
5  route2   46.0
6  route2   37.0
7  route2    2.0

If you have some columns to protect, use id_vars=['col1', 'col2', ...] to not flatten them.