I need to pick out "x" number of non-repeating, random numbers out of a list. For example:

```
all_data = [1, 2, 2, 3, 4, 5, 6, 7, 8, 8, 9, 10, 11, 11, 12, 13, 14, 15, 15]

```

How do I pick out a list like `[2, 11, 15]` and not `[3, 8, 8]`?