How to identify generator/iterator objects?

[Leo Kislov]

Kenneth McDonald wrote:
> I'm trying to write a 'flatten' generator which, when give a
> generator/iterator that can yield iterators, generators, and other data
> types, will 'flatten' everything so that it in turns yields stuff by
> simply yielding the instances of other types, and recursively yields the
> stuff yielded by the gen/iter objects.
>
> To do this, I need to determine (as fair as I can see), what are
> generator and iterator objects. Unfortunately:
>
>  >>> iter("abc")
> <iterator object at 0x61d90>
>  >>> def f(x):
> ...     for s in x: yield s
> ...
>  >>> f
> <function f at 0x58230>
>  >>> f.__class__
> <type 'function'>
>
> So while I can identify iterators, I can't identify generators by class.

But f is not a generator, it's a function returning generator:

>>> def f():
...     print "Hello"
...     yield 1
...
>>> iter(f)
Traceback (most recent call last):
  File "<input>", line 1, in ?
TypeError: iteration over non-sequence
>>> iter(f())
<generator object at 0x016C7238>
>>> type(f())
<type 'generator'>
>>> 

Notice, there is no side effect of calling f function.

  -- Leo