Hello

I'm trying to understand why the following doesn't work:

```
> n = [[1, 2, 3], [4, 5, 6, 7, 8, 9]]
>
> def flatten(lists):
> results = []
> for numbers in lists:
> for x in numbers:
> results.append(numbers[x])
> return results
>
> print flatten(n)
```

Yet, this works:

```
> n = [[1, 2, 3], [4, 5, 6, 7, 8, 9]]
>
> def flatten(lists):
> results = []
> for numbers in lists:
> for x in range(len(numbers)):
> results.append(numbers[x])
> return results
>
> print flatten(n)
```

If, "for numbers in lists:" iterates through the list of lists successfully, why can't "for x in numbers" iterate through the numbers which are within the lists of the parent list?