[lehmannro]

A property which is exposed by the article's solution too:

   >>> x = (lambda: (yield 1))() # generator with one step
   >>> y = tuple(x)[0]
   >>> y
   1
   >>> list(x) # exhausted
   []

   >>> x = (lambda: (yield 1))()
   >>> y, = x
   >>> y
   1
   >>> list(x) # exhausted, too!
   []

Because that's just what you inevitably need to do to fetch a value from a generator. There is no peeking action or some such.