Hi all, I apologize for taking so long to reply, but neither my work schedule
nor the weather have been kind in the past week. That said, I've been thinking
long and hard about what everyone has said, and have decided that it would be
useful to write a wrap-up email that attempts to
On Feb 26, 2015, at 7:04 PM, Fabio Zadrozny fabi...@gmail.com wrote:
On Wed, Feb 25, 2015 at 9:46 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 24, 2015, at 8:23 AM, Fabio Zadrozny fabi...@gmail.com wrote:
Hi Cem,
I didn't read the whole long thread, but I thought I'd point you to
On Feb 26, 2015, at 2:54 PM, Ian Kelly ian.g.ke...@gmail.com wrote:
On Feb 26, 2015 4:00 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 26, 2015, at 12:36 AM, Gregory Ewing greg.ew...@canterbury.ac.nz
wrote:
Cem Karan wrote:
I think I see what you're talking about now. Does
On Feb 26, 2015, at 3:00 PM, Ethan Furman et...@stoneleaf.us wrote:
On 02/26/2015 11:54 AM, Ian Kelly wrote:
Sometimes I wonder whether anybody reads my posts.
It's entirely possible the OP wasn't ready to understand your solution four
days ago, but two days later the OP was.
Thank you
On Mon, Mar 2, 2015 at 4:04 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 26, 2015, at 2:54 PM, Ian Kelly ian.g.ke...@gmail.com wrote:
On Feb 26, 2015 4:00 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 26, 2015, at 12:36 AM, Gregory Ewing greg.ew...@canterbury.ac.nz
wrote:
Cem
On 02/26/2015 11:54 AM, Ian Kelly wrote:
Sometimes I wonder whether anybody reads my posts.
It's entirely possible the OP wasn't ready to understand your solution four
days ago, but two days later the OP was.
--
~Ethan~
signature.asc
Description: OpenPGP digital signature
--
On Feb 26, 2015 4:00 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 26, 2015, at 12:36 AM, Gregory Ewing greg.ew...@canterbury.ac.nz
wrote:
Cem Karan wrote:
I think I see what you're talking about now. Does WeakMethod
(https://docs.python.org/3/library/weakref.html#weakref.WeakMethod)
On Feb 26, 2015, at 12:36 AM, Gregory Ewing greg.ew...@canterbury.ac.nz wrote:
Cem Karan wrote:
I think I see what you're talking about now. Does WeakMethod
(https://docs.python.org/3/library/weakref.html#weakref.WeakMethod) solve
this problem?
Yes, that looks like it would work.
Cool!
On Wed, Feb 25, 2015 at 9:46 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 24, 2015, at 8:23 AM, Fabio Zadrozny fabi...@gmail.com wrote:
Hi Cem,
I didn't read the whole long thread, but I thought I'd point you to what
I'm using in PyVmMonitor (http://www.pyvmmonitor.com/) -- which may
On Feb 24, 2015, at 4:19 PM, Gregory Ewing greg.ew...@canterbury.ac.nz wrote:
random...@fastmail.us wrote:
On Tue, Feb 24, 2015, at 00:20, Gregory Ewing wrote:
This is why I suggested registering a listener object
plus a method name instead of a callback. It avoids that
reference cycle,
On Feb 24, 2015, at 8:23 AM, Fabio Zadrozny fabi...@gmail.com wrote:
Hi Cem,
I didn't read the whole long thread, but I thought I'd point you to what I'm
using in PyVmMonitor (http://www.pyvmmonitor.com/) -- which may already cover
your use-case.
Take a look at the callback.py at
Cem Karan wrote:
I think I see what you're talking about now. Does WeakMethod
(https://docs.python.org/3/library/weakref.html#weakref.WeakMethod) solve
this problem?
Yes, that looks like it would work.
--
Greg
--
https://mail.python.org/mailman/listinfo/python-list
random...@fastmail.us wrote:
On Tue, Feb 24, 2015, at 00:20, Gregory Ewing wrote:
This is why I suggested registering a listener object
plus a method name instead of a callback. It avoids that
reference cycle, because there is no long-lived callback
object keeping a reference to the listener.
I'm combining two messages into one,
On Feb 24, 2015, at 12:29 AM, random...@fastmail.us wrote:
On Tue, Feb 24, 2015, at 00:20, Gregory Ewing wrote:
Cem Karan wrote:
I tend to structure my code as a tree or DAG of objects. The owner refers
to
the owned object, but the owned object has no
On Feb 23, 2015, at 7:29 AM, Frank Millman fr...@chagford.com wrote:
Cem Karan cfkar...@gmail.com wrote in message
news:a3c11a70-5846-4915-bb26-b23793b65...@gmail.com...
Good questions! That was why I was asking about 'gotchas' with WeakSets
originally. Honestly, the only way to
Cem Karan wrote:
On Feb 21, 2015, at 12:27 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
The simplest possible identity-based scheme would be something like this:
# don't hate me for using a global variable
CALLBACKS = []
def register(func):
if func not in
Cem Karan cfkar...@gmail.com wrote in message
news:a3c11a70-5846-4915-bb26-b23793b65...@gmail.com...
Good questions! That was why I was asking about 'gotchas' with WeakSets
originally. Honestly, the only way to know for sure would be to write two
APIs for doing similar things, and then
On Feb 22, 2015, at 5:29 PM, Laura Creighton l...@openend.se wrote:
In a message of Sun, 22 Feb 2015 17:09:01 -0500, Cem Karan writes:
Documentation is a given; it MUST be there. That said, documenting
something, but still making it surprising, is a bad idea. For
example, several people
Cem Karan wrote:
I tend to structure my code as a tree or DAG of objects. The owner refers to
the owned object, but the owned object has no reference to its owner. With
callbacks, you get cycles, where the owned owns the owner.
This is why I suggested registering a listener object
plus a
On Feb 21, 2015, at 12:08 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info:
Other than that, I cannot see how calling a function which has *not*
yet been garbage collected can fail, just because the only reference
still existing is a weak
Cem Karan cfkar...@gmail.com:
On Feb 21, 2015, at 12:08 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Maybe the logic of the receiving object isn't prepared for the callback
anymore after an intervening event.
The problem then, of course, is in the logic and not in the callbacks.
This was
On Feb 21, 2015, at 12:27 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
Cem Karan wrote:
On Feb 21, 2015, at 8:15 AM, Chris Angelico ros...@gmail.com wrote:
On Sun, Feb 22, 2015 at 12:13 AM, Cem Karan cfkar...@gmail.com wrote:
OK, so it would violate the principle of
On Feb 22, 2015, at 7:12 AM, Marko Rauhamaa ma...@pacujo.net wrote:
Cem Karan cfkar...@gmail.com:
On Feb 21, 2015, at 11:03 AM, Marko Rauhamaa ma...@pacujo.net wrote:
I use callbacks all the time but haven't had any problems with strong
references.
I am careful to move my objects to a
Cem Karan cfkar...@gmail.com:
You were saying that you move your objects into a zombie state. I
assumed that you meant you marked them in some manner (e.g., setting
'is_zombie' to True),
Yes, but even better:
self.set_state(ZOMBIE)
so that anything that has a strong reference to the
On Feb 22, 2015, at 7:24 AM, Chris Angelico ros...@gmail.com wrote:
On Sun, Feb 22, 2015 at 11:07 PM, Cem Karan cfkar...@gmail.com wrote:
Correct. The GUI engine ultimately owns everything. Of course, this is
a very simple case (imagine a little notification popup; you don't
care about it,
Marko Rauhamaa wrote:
Chris Angelico ros...@gmail.com:
On Sun, Feb 22, 2015 at 7:34 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Refloops are not to be worried about, let alone removed.
Why?
Because the whole point of GC-languages is that you should stop worrying
about memory. Trying to
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info:
I don't know about Java's Hotspot, but I do know that CPython's ref counting
garbage collector has at least one advantage over the GC used by Jython and
IronPython: unlike them, open files are closed as soon as they are no
longer in use.
On Feb 22, 2015, at 7:46 AM, Marko Rauhamaa ma...@pacujo.net wrote:
Cem Karan cfkar...@gmail.com:
On Feb 21, 2015, at 12:08 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Maybe the logic of the receiving object isn't prepared for the callback
anymore after an intervening event.
The problem
On Feb 22, 2015, at 5:15 AM, Gregory Ewing greg.ew...@canterbury.ac.nz wrote:
Frank Millman wrote:
In order to inform users that certain bits of state have changed, I require
them to register a callback with my code.
This sounds to me like a pub/sub scenario. When a 'listener' object comes
On Sun, Feb 22, 2015 at 11:07 PM, Cem Karan cfkar...@gmail.com wrote:
Correct. The GUI engine ultimately owns everything. Of course, this is
a very simple case (imagine a little notification popup; you don't
care about it, you don't need to know when it's been closed, the only
event on it is
On Feb 21, 2015, at 11:03 AM, Marko Rauhamaa ma...@pacujo.net wrote:
Chris Angelico ros...@gmail.com:
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users that certain bits of state have changed, I
require them to register a callback with my code.
On Feb 21, 2015, at 3:57 PM, Grant Edwards invalid@invalid.invalid wrote:
On 2015-02-21, Cem Karan cfkar...@gmail.com wrote:
On Feb 21, 2015, at 12:42 AM, Chris Angelico ros...@gmail.com wrote:
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users
On Sun, Feb 22, 2015 at 8:14 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Helping it along means your program doesn't waste memory. Why such a
blanket statement?
Because worrying Python programmers with evil spirits (reference loops)
leads to awkward coding practices and takes away one of the
Chris Angelico wrote:
On Sun, Feb 22, 2015 at 3:38 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
But you are using it. You might not be using it by name, but you are
using it via the callback function. What did you expect, that Python
should read your mind and somehow
On Sun, Feb 22, 2015 at 9:32 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
Why? Do you expect that the Python garbage collector special cases callbacks
to keep them alive even when there are no references to them? How would it
distinguish a callback from some other function?
somebody, I got confused with the indent level wrote:
They force the use of the much slower cycle-detecting GC, rather than
the quick and efficient CPython refcounter.
Somebody has misunderstood something here. When it comes to efficient
garbage collectors, refcounting is a turtle. The
On Feb 21, 2015, at 10:55 AM, Chris Angelico ros...@gmail.com wrote:
On Sun, Feb 22, 2015 at 2:45 AM, Cem Karan cfkar...@gmail.com wrote:
OK, so if I'm reading your code correctly, you're breaking the cycle in your
object graph by making the GUI the owner of the callback, correct? No other
Cem Karan cfkar...@gmail.com:
On Feb 21, 2015, at 11:03 AM, Marko Rauhamaa ma...@pacujo.net wrote:
I use callbacks all the time but haven't had any problems with strong
references.
I am careful to move my objects to a zombie state after they're done so
they can absorb any potential loose
Chris Angelico wrote:
On Sun, Feb 22, 2015 at 9:32 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
Why? Do you expect that the Python garbage collector special cases
callbacks to keep them alive even when there are no references to them?
How would it distinguish a callback
On Mon, Feb 23, 2015 at 12:45 AM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
No no no. It's the other way around. _Something_ has to be doing those
callbacks, and it's that _something_ that should be keeping them
alive. The fact that it's a registered callback should itself
On Feb 22, 2015, at 7:52 AM, Laura Creighton l...@openend.se wrote:
In a message of Sun, 22 Feb 2015 07:16:14 -0500, Cem Karan writes:
This was PRECISELY the situation I was thinking about. My hope was
to make the callback mechanism slightly less surprising by allowing
the user to track
Frank Millman wrote:
In order to inform users that certain bits of state have changed, I require
them to register a callback with my code.
This sounds to me like a pub/sub scenario. When a 'listener' object comes
into existence it is passed a reference to a 'controller' object that holds
In a message of Sun, 22 Feb 2015 07:16:14 -0500, Cem Karan writes:
This was PRECISELY the situation I was thinking about. My hope was
to make the callback mechanism slightly less surprising by allowing
the user to track them, releasing them when they aren't needed
without having to figure out
On Sun, Feb 22, 2015 at 6:52 PM, Marko Rauhamaa ma...@pacujo.net wrote:
What I mean, though, is that you shouldn't think you need to create
object destructors where you routinely set all members to None.
Sure, not *routinely*. It'd be a special case where it's not
specifically a destructor, and
Chris Angelico ros...@gmail.com:
Or (a very common case for me) a callback saying remote end is gone
(eg on a socket) might wipe out the callbacks, thus removing their
refloops.
Refloops are not to be worried about, let alone removed.
Marko
--
On Sun, Feb 22, 2015 at 7:34 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Chris Angelico ros...@gmail.com:
Or (a very common case for me) a callback saying remote end is gone
(eg on a socket) might wipe out the callbacks, thus removing their
refloops.
Refloops are not to be worried about, let
Chris Angelico ros...@gmail.com:
On Sun, Feb 22, 2015 at 7:34 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Refloops are not to be worried about, let alone removed.
Why?
Because the whole point of GC-languages is that you should stop worrying
about memory. Trying to mastermind and micromanage
On Mon, Feb 23, 2015 at 9:29 AM, Laura Creighton l...@openend.se wrote:
But that is not so surprising. How many people use WeakSets for
_anything_? I've never used them, aside from 'ooh! cool shiny
new language feature! Let's kick it around the park!' That people
aren't familiar with
On 02/22/2015 05:13 AM, Cem Karan wrote:
Output:
From Evil Zombie: Surprise!
From Your Significant Other: Surprise!
In this case, the user made an error (just as Marko said in his earlier
message),
and forgot about the callback he registered with the library. The callback
isn't
Cem Karan cfkar...@gmail.com:
My goal is to make things as pythonic (whatever that means in this
case) and obvious as possible. Ideally, a novice can more or less
guess what will happen with my API without really having to read the
documentation on it.
If you try to shield your user from the
On Feb 22, 2015, at 4:34 PM, Marko Rauhamaa ma...@pacujo.net wrote:
Cem Karan cfkar...@gmail.com:
My goal is to make things as pythonic (whatever that means in this
case) and obvious as possible. Ideally, a novice can more or less
guess what will happen with my API without really having to
In a message of Sun, 22 Feb 2015 17:09:01 -0500, Cem Karan writes:
Documentation is a given; it MUST be there. That said, documenting
something, but still making it surprising, is a bad idea. For
example, several people have been strongly against using a WeakSet to
hold callbacks because they
On Feb 22, 2015, at 4:02 PM, Ethan Furman et...@stoneleaf.us wrote:
On 02/22/2015 05:13 AM, Cem Karan wrote:
Output:
From Evil Zombie: Surprise!
From Your Significant Other: Surprise!
In this case, the user made an error (just as Marko said in his earlier
message),
and forgot about
On Sun, Feb 22, 2015 at 7:22 AM, Cem Karan cfkar...@gmail.com wrote:
On Feb 22, 2015, at 5:15 AM, Gregory Ewing greg.ew...@canterbury.ac.nz
wrote:
Frank Millman wrote:
In order to inform users that certain bits of state have changed, I
require them to register a callback with my code.
On Sun, Feb 22, 2015 at 1:04 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
Marko Rauhamaa wrote:
Grant Edwards invalid@invalid.invalid:
the polite thing to do is to delete references to it when you're done
with it.
I disagree with that recommendation. You should do the
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info:
Marko Rauhamaa wrote:
Grant Edwards invalid@invalid.invalid:
the polite thing to do is to delete references to it when you're done
with it.
I disagree with that recommendation. You should do the natural thing and
not care who holds
Grant Edwards invalid@invalid.invalid:
the polite thing to do is to delete references to it when you're done
with it.
I disagree with that recommendation. You should do the natural thing and
not care who holds references to who.
Marko
--
https://mail.python.org/mailman/listinfo/python-list
On Sat, Feb 21, 2015 at 1:57 PM, Grant Edwards invalid@invalid.invalid wrote:
On 2015-02-21, Cem Karan cfkar...@gmail.com wrote:
On Feb 21, 2015, at 12:42 AM, Chris Angelico ros...@gmail.com wrote:
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users
On Sun, Feb 22, 2015 at 3:38 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
But you are using it. You might not be using it by name, but you are using
it via the callback function. What did you expect, that Python should read
your mind and somehow intuit that you still care
Chris Angelico wrote:
On Sun, Feb 22, 2015 at 1:04 PM, Steven D'Aprano
steve+comp.lang.pyt...@pearwood.info wrote:
Marko Rauhamaa wrote:
Grant Edwards invalid@invalid.invalid:
the polite thing to do is to delete references to it when you're done
with it.
I disagree with that
Marko Rauhamaa wrote:
Grant Edwards invalid@invalid.invalid:
the polite thing to do is to delete references to it when you're done
with it.
I disagree with that recommendation. You should do the natural thing and
not care who holds references to who.
I don't understand this. What is the
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote in message
news:54e8af1b$0$12976$c3e8da3$54964...@news.astraweb.com...
Frank Millman wrote:
I tried something similar a while ago, and I did find a gotcha.
The problem lies in this phrase - if they are no longer alive, they are
On Feb 21, 2015, at 9:36 AM, Chris Angelico ros...@gmail.com wrote:
On Sun, Feb 22, 2015 at 1:07 AM, Cem Karan cfkar...@gmail.com wrote:
I agree about closures; its the only way they could work. When I was
originally thinking about the library, I was trying to include all types of
On Sun, Feb 22, 2015 at 2:45 AM, Cem Karan cfkar...@gmail.com wrote:
OK, so if I'm reading your code correctly, you're breaking the cycle in your
object graph by making the GUI the owner of the callback, correct? No other
chunk of code has a reference to the callback, correct?
Correct. The
Chris Angelico ros...@gmail.com:
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users that certain bits of state have changed, I
require them to register a callback with my code. The problem is that
when I store these callbacks, it naturally creates a
Frank Millman wrote:
I tried something similar a while ago, and I did find a gotcha.
The problem lies in this phrase - if they are no longer alive, they are
automatically removed from the WeakSet, preventing me from accidentally
calling them when they are dead.
I found that the reference
Cem Karan wrote:
On Feb 21, 2015, at 8:15 AM, Chris Angelico ros...@gmail.com wrote:
On Sun, Feb 22, 2015 at 12:13 AM, Cem Karan cfkar...@gmail.com wrote:
OK, so it would violate the principle of least surprise for you.
Interesting. Is this a general pattern in python? That is,
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info:
Other than that, I cannot see how calling a function which has *not*
yet been garbage collected can fail, just because the only reference
still existing is a weak reference.
Maybe the logic of the receiving object isn't prepared for the
On Feb 21, 2015, at 12:42 AM, Chris Angelico ros...@gmail.com wrote:
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users that certain bits of state have changed, I require
them to register a callback with my code. The problem is that when I store
On 21/02/2015 05:41, Frank Millman wrote:
Cem Karan cfkar...@gmail.com wrote in message
news:33677ae8-b2fa-49f9-9304-c8d937842...@gmail.com...
Hi all, I'm working on a project that will involve the use of callbacks,
and I want to bounce an idea I had off of everyone to make sure I'm not
On Feb 21, 2015, at 8:15 AM, Chris Angelico ros...@gmail.com wrote:
On Sun, Feb 22, 2015 at 12:13 AM, Cem Karan cfkar...@gmail.com wrote:
OK, so it would violate the principle of least surprise for you.
Interesting. Is this a general pattern in python? That is, callbacks are
owned by
On Fri, Feb 20, 2015 at 9:42 PM, Chris Angelico ros...@gmail.com wrote:
No, it's not. I would advise using strong references - if the callback
is a closure, for instance, you need to hang onto it, because there
are unlikely to be any other references to it. If I register a
callback with you, I
On Sun, Feb 22, 2015 at 12:13 AM, Cem Karan cfkar...@gmail.com wrote:
OK, so it would violate the principle of least surprise for you.
Interesting. Is this a general pattern in python? That is, callbacks are
owned by what they are registered with?
In the end, I want to make a library
On Feb 21, 2015, at 12:41 AM, Frank Millman fr...@chagford.com wrote:
Cem Karan cfkar...@gmail.com wrote in message
news:33677ae8-b2fa-49f9-9304-c8d937842...@gmail.com...
Hi all, I'm working on a project that will involve the use of callbacks,
and I want to bounce an idea I had off of
On Feb 21, 2015, at 8:37 AM, Mark Lawrence breamore...@yahoo.co.uk wrote:
On 21/02/2015 05:41, Frank Millman wrote:
Cem Karan cfkar...@gmail.com wrote in message
news:33677ae8-b2fa-49f9-9304-c8d937842...@gmail.com...
Hi all, I'm working on a project that will involve the use of callbacks,
On Sun, Feb 22, 2015 at 1:07 AM, Cem Karan cfkar...@gmail.com wrote:
I agree about closures; its the only way they could work. When I was
originally thinking about the library, I was trying to include all types of
callbacks, including closures and callable objects. The callable objects may
On 2015-02-21, Cem Karan cfkar...@gmail.com wrote:
On Feb 21, 2015, at 12:42 AM, Chris Angelico ros...@gmail.com wrote:
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users that certain bits of state have changed, I require
them to register a
Hi all, I'm working on a project that will involve the use of callbacks, and I
want to bounce an idea I had off of everyone to make sure I'm not developing a
bad idea. Note that this is for python 3.4 code; I don't need to worry about
any version of python earlier than that.
In order to
On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan cfkar...@gmail.com wrote:
In order to inform users that certain bits of state have changed, I require
them to register a callback with my code. The problem is that when I store
these callbacks, it naturally creates a strong reference to the objects,
Cem Karan cfkar...@gmail.com wrote in message
news:33677ae8-b2fa-49f9-9304-c8d937842...@gmail.com...
Hi all, I'm working on a project that will involve the use of callbacks,
and I want to bounce an idea I had off of everyone to make sure I'm not
developing a bad idea. Note that this is for
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