[Tutor] build list of non-empty variables

[Tim Golden]

Alan Gauld wrote:
> In fact I guess you could say that the new definition of a list
> comprehension is
> 
> [ generator expression]

Well, not if sure if you meant that literally, but
it's certainly not: that would be a list whose one
item was a generator expression:

<code>
squares = (x * x for x in range (10))
l = [squares]

print len (l)
print l[0]

</code>

But a list comp *is* (in effect) the same as:

<code>
squares = (x * x for x in range (10))
l = list (squares)

print len (l)
print l[0]

</code>


TJG