Re: Setting a read-only attribute
On Aug 30, 11:35 pm, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. How can I go about this? Cheers. -T Could you show the object you want to set his attribute? Until that, it's difficult to answer to you. PS: If the attribut is on read only, their must a good reason for that ;) -- http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
[EMAIL PROTECTED] wrote: I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. How can I go about this? This seems like a bizarre requirement. Why is the attribute read-only in the first place? How is the read-only mechanism enforced? Is the object created in Python or in an extension module? Do you have any evidence that setting the attribute will effect the required change in the behavior of the object. A little more information would be helpful. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://del.icio.us/steve.holden --- Asciimercial -- Get on the web: Blog, lens and tag the Internet Many services currently offer free registration --- Thank You for Reading - -- http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
On Aug 31, 6:14 pm, Alexandre Badez [EMAIL PROTECTED] wrote:
On Aug 30, 11:35 pm, [EMAIL PROTECTED] [EMAIL PROTECTED]
wrote:
I have an object and wish to set an attribute on it which,
unfortunately for me, is read-only.
How can I go about this?
Cheers.
-T
Could you show the object you want to set his attribute?
Until that, it's difficult to answer to you.
PS: If the attribut is on read only, their must a good reason for
that ;)
Hi all,
Thanks for all the responses. What I'm trying to do is kludge around
something. sys.settrace takes a method whose arguments are (frame,
event, arg). I want to have a tracer class which can be instantiated
and listen in on these trace calls.
Another way to go about it *might* be to have a module-level list of
registered Tracer objects which a module-level trace method informs of
events. It would probably be easier. In fact, I'll go do that.
*That said*, I still think it makes sense to be able to have objects
register with sys.settrace.
So what I did then was declare a static method with the same pattern
expected by sys.settrace. I then want to use something like __dict__
or __setattr__ to give that method a reference to the owning object.
And this is what I'm trying to do -- declare a static method, then un-
static it by adding a reference to the callable object...
Here's some code:
import sys
class Tracer:
'''
Instantiate this in order to access program trace information.
'''
def _getcallback(self):
@staticmethod
def callback(frame, event, arg):
print tracing ..., tracerReference
#print line , frame.f_lineno, frame.f_locals
return callback
def startTrace(self):
callback = self._getcallback()
callback.__dict__['tracerReference'] = self
sys.settrace(callback)
def foo(dict):
for i in range(2):
pass
if __name__ == __main__:
t = Tracer()
t.startTrace()
foo({1 : 5})
--
http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
[EMAIL PROTECTED] wrote:
On Aug 31, 6:14 pm, Alexandre Badez [EMAIL PROTECTED] wrote:
On Aug 30, 11:35 pm, [EMAIL PROTECTED] [EMAIL PROTECTED]
wrote:
I have an object and wish to set an attribute on it which,
unfortunately for me, is read-only.
How can I go about this?
Cheers.
-T
Could you show the object you want to set his attribute?
Until that, it's difficult to answer to you.
PS: If the attribut is on read only, their must a good reason for
that ;)
Hi all,
Thanks for all the responses. What I'm trying to do is kludge around
something. sys.settrace takes a method whose arguments are (frame,
event, arg). I want to have a tracer class which can be instantiated
and listen in on these trace calls.
Another way to go about it *might* be to have a module-level list of
registered Tracer objects which a module-level trace method informs of
events. It would probably be easier. In fact, I'll go do that.
*That said*, I still think it makes sense to be able to have objects
register with sys.settrace.
So what I did then was declare a static method with the same pattern
expected by sys.settrace. I then want to use something like __dict__
or __setattr__ to give that method a reference to the owning object.
And this is what I'm trying to do -- declare a static method, then un-
static it by adding a reference to the callable object...
Here's some code:
import sys
class Tracer:
'''
Instantiate this in order to access program trace information.
'''
def _getcallback(self):
@staticmethod
def callback(frame, event, arg):
print tracing ..., tracerReference
#print line , frame.f_lineno, frame.f_locals
return callback
def startTrace(self):
callback = self._getcallback()
callback.__dict__['tracerReference'] = self
sys.settrace(callback)
def foo(dict):
for i in range(2):
pass
if __name__ == __main__:
t = Tracer()
t.startTrace()
foo({1 : 5})
Surely the thing to do, if I understand you, is to declare callback as a
standard method and then pass a reference to a bound method (the most
obvious candidate being self.callback) to sys.settrace().
[EMAIL PROTECTED] ~/Projects/Python
$ cat test05.py
import sys
class Tracer:
'''
Instantiate this in order to access program trace information.
'''
def callback(self, frame, event, arg):
print tracing ..., self
print line , frame.f_lineno, frame.f_locals
def startTrace(self):
sys.settrace(self.callback)
def foo(dict):
for i in range(2):
pass
if __name__ == __main__:
t = Tracer()
t.startTrace()
foo({1 : 5})
[EMAIL PROTECTED] ~/Projects/Python
$ python test05.py
tracing ... __main__.Tracer instance at 0x7ff2514c
line 19 {'dict': {1: 5}}
[EMAIL PROTECTED] ~/Projects/Python
$
Does this do what you want?
regards
Steve
--
Steve Holden+1 571 484 6266 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://del.icio.us/steve.holden
--- Asciimercial --
Get on the web: Blog, lens and tag the Internet
Many services currently offer free registration
--- Thank You for Reading -
--
http://mail.python.org/mailman/listinfo/python-list
Setting a read-only attribute
I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. How can I go about this? Cheers. -T -- http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
On Aug 30, 10:35 pm, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. If it's read-only then you can't set it! How can I go about this? Joke aside, I think you need to be more specific. -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
Arnaud Delobelle wrote: On Aug 30, 10:35 pm, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. If it's read-only then you can't set it! How can I go about this? Joke aside, I think you need to be more specific. To be more specific about much more specific you should be: If you know the exact problem/hurdle you have to overcome, explain it. Otherwise kindly provide the traceback (error message) you get when attempting to set the attribute. /W -- http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
[EMAIL PROTECTED] wrote: I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. How can I go about this? Cheers. -T I guess we all need an code example to show us the way 'read only' is implemented. If you cant access to the class wich you are instantiated from, well, maybe you can just post the error or exception you get. Cheers. Gerardo -- http://mail.python.org/mailman/listinfo/python-list
Re: Setting a read-only attribute
[EMAIL PROTECTED] wrote: I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. How can I go about this? Can you simply subclass the object's class, intercept __setattr__ and __getattribute__, and spoof the read-only attribute? E.g.: class A(object): def get_ro(self): return 'readonly' ro = property(get_ro) class B(A): def __setattr__(self, anatt, aval): if anatt == 'ro': anatt = '_ro' super(A, self).__setattr__(anatt, aval) def __getattribute__(self, anatt): if anatt == 'ro' and hasattr(self, '_ro'): anatt = '_ro' return super(A, self).__getattribute__(anatt) The output: py class A(object): ... def get_ro(self): ... return 'readonly' ... ro = property(get_ro) ... py class B(A): ... def __setattr__(self, anatt, aval): ... if anatt == 'ro': ...anatt = '_ro' ... super(A, self).__setattr__(anatt, aval) ... def __getattribute__(self, anatt): ... if anatt == 'ro' and hasattr(self, '_ro'): ... anatt = '_ro' ... return super(A, self).__getattribute__(anatt) ... py a = A() py print a.ro readonly py a.ro = 4 Traceback (most recent call last): File ipython console, line 1, in module type 'exceptions.AttributeError': can't set attribute py py b = B() py b.x = 10 py print b.x 10 py print b.ro readonly py b.ro = 4 py print b.ro 4 I'm not so sure this is the least clunky way to do this. James -- James Stroud UCLA-DOE Institute for Genomics and Proteomics Box 951570 Los Angeles, CA 90095 http://www.jamesstroud.com/ -- http://mail.python.org/mailman/listinfo/python-list
