I have a dataframe:

```
Number   Items
 1        1,3,7
 2        1,2,7
 3        4,5
 4        9

```

I need to flag if any of `Items` values exist in the `Number` column for each row.

Output should be:

```
Number   Items      Flag
 1        1,3,7      True
 2        1,2,7      True  
 3        4,5        False
 4        9          False

```

What I have tried is: `df['Flag'] = df.items.isin(df.Number)`

This works when there is just one value in the `Items` column. I need to account for multiple values so that `1,3,7` are check individually and not just as a whole.