List comprehension example in 1-intro correction

I'm not a python expert but a starter. I use it at work sometimes for quick scripting. What I mean is that as a newbie I maybe wrong in my observation.

I was checking the 1 - Intro lesson and notice in Readme.md the following code:

```python
newlist = [x * 2 for number in sample]
```

and I receive the following error:
```python
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
```

Reading the given documentation at http://docs.python.org/tutorial/datastructures.html#list-comprehensions, I concluded the code should be:
```python
newlist = [x * 2 for x in sample]
```
or 

```python
newlist = [number * 2 for number in sample]
```

I have the feeling the latest is way more descriptive, that's why I choose it.