I'd like to convert to below `Df1` to `Df2`. 

The empty values would be filled with `Nan`. 

Below Dfs are examples. 

* My data has weeks from 1 to 8.
* IDs are 100,000.
* Only week 8 has all IDs, so total rows will be 100,000.

I have Df3 which has 100,000 of id, and I want to merge df1 on Df3 formatted as df2.

ex) `pd.merge(df3, df1, on="id", how="left")` -> but, formatted as `df2`

```
 Df1>
 wk, id, col1, col2  ...
 1    1   0.5  15  
 2    2   0.5  15  
 3    3   0.5  15  
 1    2   0.5  15  
 3    2   0.5  15  

 ------
 Df2>
 wk1, id, col1, col2, wk2, id, col1, col2, wk3,  id, col1, col2,...
 1    1   0.5  15      2    1   Nan   Nan   3    1   Nan   Nan
 1    2   0.5  15      2    2   0.5  15     3    2   0.5    15
 1    3   Nan  Nan     2    3   Nan   Nan   3    3   0.5    15

```