Python 2.7.5+ (default, Sep 19 2013, 13:48:49)
>>> queue = []
>>> n = 10
>>> for i in range(0, n-1):
... queue.append(pow(-1,i)/((2*i)+1))
...
>>> queue
[1, -1, 0, -1, 0, -1, 0, -1, 0]
>>> sum(queue)
-3
>>> queue = [pow(-1,i)/((2*i)+1) for i in range(0, n-1)]
>>> sum(queue)
-3
>>>
If you don't need the temporary list, you can use a generator:
>>> sum(pow(-1,i)/((2*i)+1) for i in range(0, n-1))
-3