I have a dataframe that looks roughly like this:

```
A1 B1 C1 A4 B4 C4 A7 B7 C7
A2 B2 C2 A5 B5 C5 A8 B8 C8
A3 B3 C3 A6 B6 C6 A9 B9 C9

```

that I would like to get looking like this:

```
A1 B1 C1
A2 B2 C2
A3 B3 C3
A4 B4 C4
A5 B5 C5
A6 B6 C6
A7 B7 C7
A8 B8 C8
A9 B9 C9

```

Is there anything built into pandas or another data processing library that can easily do this without manually traversing the rows 3 (in this example) times for each "column set"? This would essentially be a 3-column pivot.