[Python-ideas] How can I get own instance of generator in itself code

[Đinh Nho Nam]

Yes, in my project, i define a decorator to call twice as I said. The code below:

def asynchronous(gen_func):
	class _generator(object):
		def __init__(self, *args, **kwargs):
			self.__generator = gen_func(*args, **kwargs)
			self.__generator.next()
			self.__generator.send(self.__generator)

		#override generator method: __iter__, next, send, ...	
			
		def __iter__(self):
			return self.__generator
		
		def next(self):
			return self.__generator.next()
			
		def send(self, arg):
			return self.__generator.send(arg)

		def close():
			return self.__generator.close()
		
		def __repr__(self):
			return repr(self.__generator)
		
	return _generator
	
	
@asynchronous
def invoke_callback(url):
	code here
	
and we only call is as function, not need call send or next method

g = invoke_callback(url)

But i think the code is still not nice, because any we have to define @asynchronous in any generator.
	




----- Original Message -----
From: "Alexandre Zani" <alexandre.zani at gmail.com>
To: "Đinh Nho Nam" <namdn at socbay.com>
Cc: python-ideas at python.org
Sent: Sunday, July 15, 2012 10:58:10 PM
Subject: Re: [Python-ideas] How can I get own instance of generator in itself code

On Sat, Jul 14, 2012 at 11:18 PM, Đinh Nho Nam <namdn at socbay.com> wrote:
> Hi Python Software Foundation!
> I have learned Python for 2 years, and I love this language very much. The structure and grammar are simple and beautiful. I used this language in most of my projects.
> Now, I learn to use generator. This architecture is very intelligent. It allows programmer can pause and resume function. I think that this feature is not supported in classic language as C++, Java, C#.. In my design, we use 1 generator in both tasks: invoke and callback when download one url. But I have a small problem when getting instance of generator. How can I get own instance of generator in itself code?
> detail pseudo code example:
>
> def invoke_callback(url):
>         do something here
>         self = get myself (invoke_callback generator) instance #how can we do as this line????
>         data = yield asynchronous_dowload(url, callback = self.next)
>         do something with data
>
> How can we do as this code. How can I get self variable?. Does the language support this feature? I cannot find it in any document in python.org. So, I have to solve it by wrapper it in a list.
>
> def invoke_callback(url, wrapper):
>         self = wrapper[0]
>         data = yield asynchronous_dowload(url, callback = self.next)
>         do something with data
>
> wrapper = []
> instance = invoke_callback(url, wrapper)
> wrapper.append(instance)
> instance.next()
>
> The other way is sending instance to itself, and we invoke twice.
>
> def invoke_callback(url):
>         self = yield
>         data = yield asynchronous_dowload(url, callback = self.next)
>         do something with data
> instance = invoke_callback(url)
> instance.next() #first
> instance.send(instance) #second
>
> But the code in both of ways is not nice. Can you add this feature in the next version of python???
> Regards
> Namdn
> _______________________________________________
> Python-ideas mailing list
> Python-ideas at python.org
> http://mail.python.org/mailman/listinfo/python-ideas

I would suggest creating a decorator for this:

def self_decorator(f):
  @functools.wraps(f)
  def decorated(*args, **kwargs):
    return f(f, *args, **kwargs)

@self_decorator
def do_stuff(self, a, b, c):
  pass

Should work for any kind of function.

And C/C++ do support such functionality in the sense that you can keep
state in between function invocations:

// This will return 1 the first time it is called, 2, the next time and so on...
int generator() {
  static int num = 0;
  num += 1;
  return num;
}

On a final note, this question more appropriate for python-list.
python-ideas is for the discussion of ideas to change python itself.

Alex