I have dataframe in following way:

```
vals = [[100,200], [100,200],[100,200]]

df = pd.DataFrame({'y':vals})
df['x'] = [1,2,3]

df

```

how can I append y values to the lists in x column, so my final values are in the following shape?

[![enter image description here](https://i.stack.imgur.com/NNuWA.png)](https://i.stack.imgur.com/NNuWA.png)

thanks