How to make an empty generator?

Robert Kern robert.kern at
Fri Feb 19 01:12:10 CET 2010

On 2010-02-18 17:33 PM, Ben Finney wrote:
> Robert Kern<robert.kern at>  writes:
>> On 2010-02-18 16:25 PM, Stephen Hansen wrote:
>>> The only way I can figure out how to make an empty generator is:
>>>       def gen():
>>>           # do my one-time processing here
>>>           return
>>>           yield
>>> Is there a better way? The return/yield just makes me flinch
>>> slightly. I tried just raising StopIteration at the end, but of
>>> course that didn't work.
> No need to define functions or classes; let a generator expression take
> care of it for you::
>      >>>  foo = (x for x in list())
>      >>>
>      Traceback (most recent call last):
>        File "<stdin>", line 1, in<module>
>      StopIteration

He doesn't want *any* empty generator. He wants an iterator that executes some 
given side-effect-producing code then immediately raises the StopIteration.

Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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