Take multiple columns and put them to the same index with pandas

Question

I have a bunch of ugly customer data that I am trying to normalise. It basically looks like this:

Customer   Order1   Order2   Order3 ... OrderN

  John      This     That     The   ...  Other
 Shelly    Thing1   Thing2   Thing3 ... ThingN
   .         .        .        .          .
   .         .        .        .          .

So I want to change it to look like:

Customer   Order

 John      This
 John      That
 John      The
 Shelly    Thing1
 Shelly    Thing2

And so on.

I am not sure how to do this, though.

Any help would be great!

Answer 1

Precisely one stack and two reset_index calls.

df
  Customer  Order1  Order2  Order3  OrderN
0     John    This    That     The   Other
1   Shelly  Thing1  Thing2  Thing3  ThingN

(df.set_index('Customer')
   .stack()
   .reset_index(level=1, drop=True)
   .reset_index(name='Order')
)

  Customer   Order
0     John    This
1     John    That
2     John     The
3     John   Other
4   Shelly  Thing1
5   Shelly  Thing2
6   Shelly  Thing3
7   Shelly  ThingN