python生成器输出值？

Question

 >>> stack = [(v for u, v in G.edges('130'))]
>>> stack
[<generator object <genexpr> at 0x09E6F120>]
>>> for i in stack:
    print i


<generator object <genexpr> at 0x09E6F120>
>>> type(stack)
<type 'list'>
>>> 

为什么不能输出stack里面的值，如何才能输出stack里面的值？

Answer 1

 for i in stack:
    for j in i:
            print(j)