#basic syntax(a function that yield)
def genMul2(N):
  for i in range(N):
   yield i * 2
for i in genMul2(5):print i
#inside for, the next method is called
#在for循环的内部，Python调用了next方法。
#下面的x叫做generator对象
x = genMul2(2)
#一直调用next方法，最后会抛出一个异常
print x
print x.next()
print x.next()
#print x.next()  !!!!error!!!!StopIteration
  

#//python/4451