Re: How to get a unique id for bound methods?
In article [EMAIL PROTECTED], Fredrik Lundh [EMAIL PROTECTED] wrote: Russell E. Owen wrote: Having looked at it again, it is familiar. I copied it when I wrote my own code. I avoided using at the time both because the initial underscore suggested it was a private method and because it introduces an extra function call. _register has the same weakness that my code had when I used id(func) -- it uses the id of the function to generate the unique tk function name, but it keeps no reference to that function. Either Tkinter is clever about keeping a reference to each callable around, or else it has the same bug I was seeing and it just doesn't show up often enough to have been caught. I should take some time and look into that. of course it keeps a reference to it; how else do you expect the Tcl command to find the right PyObjects? Right. Of course. I started out emulating the code for _register but over time made various incremental changes. Eventually I messed up and started taking the id of the wrong thing. I was able to fix that and all is well -- without having to use the mysterious hash function. I also now keep a reference to the tk function name so I can properly delete it when finished. That eliminates a small memory leak. Thanks for all your help. -- Russell -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
Russell E. Owen wrote: I have several situations in my code where I want a unique identifier for a method of some object (I think this is called a bound method). I want this id to be both unique to that method and also stable (so I can regenerate it later if necessary). def persistent_bound_method(m): ... return m.im_self.__dict__.setdefault(m.im_func.func_name, m) ... class A: ... def x(self): ... return ... a=A() a.x is a.x False persistent_bound_method(a.x) is persistent_bound_method(a.x) True -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
In article [EMAIL PROTECTED], Fredrik Lundh [EMAIL PROTECTED] wrote: Russell E. Owen wrote: The current issue is associated with Tkinter. I'm trying to create a tk callback function that calls a python function (any python callable entity). To do that, I have to create a name for tk that is unique to my python function. A hash-like name would be perfect, meaning a name that is always the same for a particular python function and always different for a different python function. That would save a lot of housekeeping. have you tried Tkinter's built-in _register method? import Tkinter w = Tkinter.Tk() help(w._register) Help on method _register in module Tkinter: _register(self, func, subst=None, needcleanup=1) method of Tkinter.Tk instance Return a newly created Tcl function. If this function is called, the Python function FUNC will be executed. An optional function SUBST can be given which will be executed before FUNC. Thanks. That looks like just the thing. I think I had seen it but was deterred by the leading underscore (suggesting an internal method whose interface might change). Still, I guess if it gets modified I can just change my code. -- Russell -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
In article [EMAIL PROTECTED], Fredrik Lundh [EMAIL PROTECTED] wrote: Russell E. Owen wrote: The current issue is associated with Tkinter. I'm trying to create a tk callback function that calls a python function (any python callable entity). To do that, I have to create a name for tk that is unique to my python function. A hash-like name would be perfect, meaning a name that is always the same for a particular python function and always different for a different python function. That would save a lot of housekeeping. have you tried Tkinter's built-in _register method? import Tkinter w = Tkinter.Tk() help(w._register) Help on method _register in module Tkinter: _register(self, func, subst=None, needcleanup=1) method of Tkinter.Tk instance Return a newly created Tcl function. If this function is called, the Python function FUNC will be executed. An optional function SUBST can be given which will be executed before FUNC. Having looked at it again, it is familiar. I copied it when I wrote my own code. I avoided using at the time both because the initial underscore suggested it was a private method and because it introduces an extra function call. _register has the same weakness that my code had when I used id(func) -- it uses the id of the function to generate the unique tk function name, but it keeps no reference to that function. Either Tkinter is clever about keeping a reference to each callable around, or else it has the same bug I was seeing and it just doesn't show up often enough to have been caught. I should take some time and look into that. It's a frustrating problem. There should be some simple way to get a unique hash-like identifier for any callable entity. If one were just using functions then id() would be fine. But bound methods are too different. I'll use hash for now, but given that Im not sure what hash is even doing, I should recode to something that I know works. -- Russell -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
Russell E. Owen wrote: Having looked at it again, it is familiar. I copied it when I wrote my own code. I avoided using at the time both because the initial underscore suggested it was a private method and because it introduces an extra function call. _register has the same weakness that my code had when I used id(func) -- it uses the id of the function to generate the unique tk function name, but it keeps no reference to that function. Either Tkinter is clever about keeping a reference to each callable around, or else it has the same bug I was seeing and it just doesn't show up often enough to have been caught. I should take some time and look into that. of course it keeps a reference to it; how else do you expect the Tcl command to find the right PyObjects? import Tkinter w = Tkinter.Tk() def f(): ... pass ... import sys sys.getrefcount(f) 2 w.register(f) '9571664f' sys.getrefcount(f) 3 del f w.tk.call(9571664f) 'None' (PyObject pointers to the callable and the interpreter object are stored in a Tcl clientData record associated with the command) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
In article [EMAIL PROTECTED],
[EMAIL PROTECTED] (Bengt Richter) wrote:
On Fri, 19 Aug 2005 16:33:22 -0700, Russell E. Owen [EMAIL PROTECTED]
wrote:
[...]
The current issue is associated with Tkinter. I'm trying to create a tk
callback function that calls a python function (any python callable
entity).
To do that, I have to create a name for tk that is unique to my python
function. A hash-like name would be perfect, meaning a name that is
always the same for a particular python function and always different
for a different python function. That would save a lot of housekeeping.
Why do you need a name? Can you post an example snippet that shows
a callback function being used with Tkinter as you would wish?
I have a feeling there is a much simpler solution than you are imagining ;-)
Here is an example (simplified from my real code; I may have introduced
an error in the process). I could switch to the twisted framework, but
this code has been working very well and it saves my users from having
to install a 3rd party package.
-- Russell
def addTkCallback(tk, func):
tkName = cb%d % hash(func)
tk.createcommand(tkNname, func)
return tkName
class TkSocket(TkBaseSocket):
def __init__(self,
addr,
port,
binary=False,
readCallback = None,
stateCallback = None,
tkSock = None,
):
...
try:
# create the socket and configure it
self._sock = self._tk.call(socket, ...)
self._tk.call(fconfigure, self._sock, ...)
# add callbacks; the write callback is just used to detect
state
readName =addTkCallback(self._tk, self._doRead)
self._tk.call('fileevent', self._sock, readable,
readName)
connName = addTkCallback(self._tk, self._doConnect)
self._tk.call('fileevent', self._sock, writable, connName
except Tkinter.TclError, e:
raise RuntimeError(e)
--
http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
Russell E. Owen wrote: The current issue is associated with Tkinter. I'm trying to create a tk callback function that calls a python function (any python callable entity). To do that, I have to create a name for tk that is unique to my python function. A hash-like name would be perfect, meaning a name that is always the same for a particular python function and always different for a different python function. That would save a lot of housekeeping. have you tried Tkinter's built-in _register method? import Tkinter w = Tkinter.Tk() help(w._register) Help on method _register in module Tkinter: _register(self, func, subst=None, needcleanup=1) method of Tkinter.Tk instance Return a newly created Tcl function. If this function is called, the Python function FUNC will be executed. An optional function SUBST can be given which will be executed before FUNC. def func(): ... print Hello ... name = w._register(func) name '10768336func' w.tk.call(name) Hello 'None' /F -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
Russell E. Owen wrote: The id of two different methods of the same object seems to be the same, and it may not be stable either. Two facts you're (apparently) unaware of are conspiring against you: 1) the id of an object is consistent for the lifetime of the object, but may be reused after the object goes away 2) methods are bound on an as-needed basis and then normally discarded (unless you do something to keep them around) An illustration: class cls(object): def meth1(self): pass def meth2(self): pass c = cls() m1 = c.meth1 print id(m1) -1209779308 m2 = c.meth1 print id(m2) -1209652732 I guess that just means bound methods aren't objects in their own right, but it surprised me. Nope, they're objects, they just don't tend to be around very long. The hash function looks promising -- it prints out consistent values if I use it instead of id in the code above. Is it stable and unique? The documentation talks about objects again, which given the behavior of id makes me pretty nervous. Any advice would be much appreciated. I think you'll get the best advice from this group if you tell us what the larger problem is that you're trying to solve. -- Benji York -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
On Fri, 19 Aug 2005 13:29:19 -0700, Russell E. Owen [EMAIL PROTECTED] wrote: I have several situations in my code where I want a unique identifier for a method of some object (I think this is called a bound method). I want this id to be both unique to that method and also stable (so I can regenerate it later if necessary). I thought the id function was the obvious choice, but it doesn't seem to work. The id of two different methods of the same object seems to be the same, and it may not be stable either. For instance: The id function works, but you are applying it to transient objects, which is what bound methods are unless you cause them to persist one way or another. class cls(object): def __init__(self): print id(self.meth1) print id(self.meth2) def meth1(self): pass def meth2(self): pass c = cls() 3741536 3741536 This means that self.meth1 only existed long enough to be passed to id, and when id was done with determining its id, self.meth1 was freed. Then self.meth2 was created, and happened to use a representation space with the same id as was used for self.meth1. If the two objects (bound methods here) existed at the same time, they would be guaranteed not to have the same id unless they were actually the same object. print id(c.meth1) 3616240 print id(c.meth2) 3616240 This happened to re-use a representation space with another id. I guess that just means bound methods aren't objects in their own right, but it surprised me. No, they are objects in their own right. You were surprised by your [mis]interpretation of the above results ;-) The hash function looks promising -- it prints out consistent values if I use it instead of id in the code above. Is it stable and unique? The documentation talks about objects again, which given the behavior of id makes me pretty nervous. Any advice would be much appreciated. If you want a particular bound method to have a stable and persistent id, make it persist, e.g., class cls(object): ... def __init__(self): ... print id(self.meth1) ... print id(self.meth2) ... def meth1(self): ... pass ... def meth2(self): ... pass ... c = cls() 49219060 49219060 print id(c.meth1) 49219020 print id(c.meth2) 49219020 Ok, those were transient, now nail a couple of bound methods down: cm1 = c.meth1 cm2 = c.meth2 And you can look at their id's all you like: print id(cm1) 49219020 print id(cm2) 49219060 print id(cm1) 49219020 print id(cm2) 49219060 But every time you just evaluate the attribute expression c.meth1 or c.meth2 you will get a new transient bound method object, with a new id: print id(c.meth1) 49219180 print id(c.meth2) 49219180 But the ones we forced to persist by binding the expression values to cm1 and cm2 above still have the same ids as before: print id(cm1) 49219020 print id(cm2) 49219060 So the question would be, why do you (think you ;-) need ids for these bound methods as such? I.e., what is the situation in your code? Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
Russell E. Owen wrote: The hash function looks promising -- it prints out consistent values if I use it instead of id in the code above. Is it stable and unique? The documentation talks about objects again, which given the behavior of id makes me pretty nervous. I dont know how the hash of a bound method is calculated,but as the function of the method is a stable and referenced object and as instances lives are in your hands,then an id(self)^id(self.meth.im_func) should be a chance for that 'hash' function. def methodId(boundMethod): return id(boundMethod.im_self)^id(boundMethod.im_func) class cls(object): def __init__(self): print methodId(self.meth1) print methodId(self.meth2) def meth1(self): pass def meth2(self): pass c = cls() print methodId(c.meth1) print methodId(c.meth2) I think this is giving what you expected. Regards Paolino ___ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
In article [EMAIL PROTECTED], Benji York [EMAIL PROTECTED] wrote: Russell E. Owen wrote: The id of two different methods of the same object seems to be the same, and it may not be stable either. Two facts you're (apparently) unaware of are conspiring against you: 1) the id of an object is consistent for the lifetime of the object, but may be reused after the object goes away 2) methods are bound on an as-needed basis and then normally discarded (unless you do something to keep them around) Thank you and Bengt Richter. You both explained it very well. The current issue is associated with Tkinter. I'm trying to create a tk callback function that calls a python function (any python callable entity). To do that, I have to create a name for tk that is unique to my python function. A hash-like name would be perfect, meaning a name that is always the same for a particular python function and always different for a different python function. That would save a lot of housekeeping. Does the built-in hash function actually do the job? If I centralize all tk callback management and keep objects that represent the tk callback around then I can avoid the whole issue. I was hoping to avoid that, because it complicates housekeeping and adds a risk of memory leaks (at least I think so; right now tk deallocates its callback functions in the few cases I care about so I don't worry about it.) -- Russell P.S. Paolino: thank you also for your kind reply. Your suggestion sounds very useful if I only want a hash for a bound function, but in this case since I want a hash for any callable entity I'm not sure it'll work. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a unique id for bound methods?
On Fri, 19 Aug 2005 16:33:22 -0700, Russell E. Owen [EMAIL PROTECTED] wrote: [...] The current issue is associated with Tkinter. I'm trying to create a tk callback function that calls a python function (any python callable entity). To do that, I have to create a name for tk that is unique to my python function. A hash-like name would be perfect, meaning a name that is always the same for a particular python function and always different for a different python function. That would save a lot of housekeeping. Why do you need a name? Can you post an example snippet that shows a callback function being used with Tkinter as you would wish? I have a feeling there is a much simpler solution than you are imagining ;-) Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
