Help with coroutine-based state machines?

[Neil Schemenauer]

Alan Kennedy <alanmk at hotmail.com> wrote:
> Differentiating generator-functions from functions.
> ---------------------------------------------------

> But there isn't a generator type in the types module?

Is that a question? :-)  Seriously, there is no generator type
because a generator-function has the same type as a function.

> So, that's a question I'd like to ask: can anyone tell me how
> to discover the generator-functions of an object, and
> differentiate them from ordinary functions?

Here's one way:

>>> def f():
...   pass
... 
>>> def g(): 
...   yield 1
... 
>>> f.func_code.co_flags & 0x20
0
>>> g.func_code.co_flags & 0x20
32

I don't recommend using it though.  The CO_GENERATOR (0x20)
constant is not available from Python code, AFAIK.

One final parting shot.  From the caller's point of view, there
is essentially no difference between:

    def f():
        return iter([1, 2, 3])

and:

    def g():
        for i in [1, 2, 3]:
            yield i

or even:

    def f2():
        return g()

Cheers,

  Neil