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For a simple greenlet/tasklet/microthreading experiment I found myself in
the need to ask the question

isgenerator(v)

but didn't find any implementation in the usual suspects - builtins or
inspect.

I was able to help myself out with a simple (out of my head, hope its

def isgenerator(v):
def _g(): yield
return type(v) == type(_g())

But I wonder why there is no such method already available?

Diez

on 22.01.2008 14:20 Diez B. Roggisch said the following:
>
> def isgenerator(v):
> def _g(): yield
> return type(v) == type(_g())
>
> But I wonder why there is no such method already available?


This tests for generator objects, and you could also use::

return type(v) is types.GeneratorType

I think that this is pretty direct already.

I also need to test for generator functions from time to time for which
I use::

def _isaGeneratorFunction(func):
'''Check the bitmask of `func` for the magic generator flag.'''
return bool(func.func_code.co_flags & CO_GENERATOR)


cheers,
stefan

Stefan Rank wrote:

> on 22.01.2008 14:20 Diez B. Roggisch said the following:
>>
>> def isgenerator(v):
>> def _g(): yield
>> return type(v) == type(_g())
>>
>> But I wonder why there is no such method already available?
>
>
> This tests for generator objects, and you could also use::
>
> return type(v) is types.GeneratorType
>
> I think that this is pretty direct already.

Not as nice as it could be, but certainly way less hackish than my approach.
Thanks!

> I also need to test for generator functions from time to time for which
> I use::
>
> def _isaGeneratorFunction(func):
> '''Check the bitmask of `func` for the magic generator flag.'''
> return bool(func.func_code.co_flags & CO_GENERATOR)

Not sure if that's not a bit too much on the dark magic side.. but good to
know that it exists.

Diez

Stefan Rank wrote:
> on 22.01.2008 14:20 Diez B. Roggisch said the following:
>> def isgenerator(v):
>> def _g(): yield
>> return type(v) == type(_g())
>>
>> But I wonder why there is no such method already available?
>
>
> This tests for generator objects, and you could also use::
>
> return type(v) is types.GeneratorType
>
> I think that this is pretty direct already.
>
> I also need to test for generator functions from time to time for which
> I use::
>
> def _isaGeneratorFunction(func):
> '''Check the bitmask of `func` for the magic generator flag.'''
> return bool(func.func_code.co_flags & CO_GENERATOR)

Can you please write a function for the inspect module + docs + a small
unit tests and submit a patch? The inspect module is missing the
isgenerator function.

Christian

On Jan 22, 7:46*am, Stefan Rank <list-e...@strank.info> wrote:
> I also need to test for generator functions from time to time for which
> I use::
>
> * *def _isaGeneratorFunction(func):
> * * * *'''Check the bitmask of `func` for the magic generator flag..'''
> * * * *return bool(func.func_code.co_flags & CO_GENERATOR)
>
> cheers,
> stefan

Might want to catch AttributeError in this routine - not all func
arguments will have a func_code attribute. See below:

class Z(object):
def __call__(*args):
for i in range(3):
yield 1

for i in Z()():
print i
# prints 1 three times

import types
print type(Z()()) == types.GeneratorType
# prints 'True'

print Z()().func_code
# raises AttributeError, doesn't have a func_code attribute

-- Paul

on 22.01.2008 16:09 Paul McGuire said the following:
> On Jan 22, 7:46 am, Stefan Rank <list-e...@strank.info> wrote:
>> I also need to test for generator functions from time to time for which
>> I use::
>>
>> def _isaGeneratorFunction(func):
>> '''Check the bitmask of `func` for the magic generator flag.'''
>> return bool(func.func_code.co_flags & CO_GENERATOR)
>>
>> cheers,
>> stefan
>
> Might want to catch AttributeError in this routine - not all func
> arguments will have a func_code attribute. See below:
>
> class Z(object):
> def __call__(*args):
> for i in range(3):
> yield 1
>
> for i in Z()():
> print i
> # prints 1 three times
>
> import types
> print type(Z()()) == types.GeneratorType
> # prints 'True'
>
> print Z()().func_code
> # raises AttributeError, doesn't have a func_code attribute

You are right about that for generator *objects*.
But _isaGeneratorFunction tests for generator *functions* (the ones you
call in order to get a generator object) and those must have a func_code.

So in your example::

>>> from compiler.consts import CO_GENERATOR
>>> Z().__call__.func_code.co_flags & CO_GENERATOR
32
>>> Z.__call__.func_code.co_flags & CO_GENERATOR
32

You have to use __call__ directly, you can't use the code-object-flag
test on the callable class instance Z(), but I think that's just as well
since this kind of test should not be necessary at all, except in rare
code parts (such as Diez' microthreading experiments).

cheers,
stefan

On Jan 22, 6:20*am, "Diez B. Roggisch" <de...@nospam.web.de> wrote:
> For a simple greenlet/tasklet/microthreading experiment I found myself in
> the need to ask the question
>
> isgenerator(v)
>
> but didn't find any implementation in the usual suspects - builtins or
> inspect.

types.GeneratorType exists in newer Pythons, but I'd suggest just
checking for a send method.
That way, you can use something that emulates the interface without
being forced to use a generator.

hasattr(ob, 'send')..