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finding the parent class (not superclass) of the currently executingmethod derived from a Borg class

P: n/a
I want to create a class derived from a Borg class that can
instantiated as part of a script or be contained in other classes.
When methods from the Borg class are called, I would like to know the
name of the class that contains the Borg class.

I've played a bit with inspect and _getframe from the sys module but
get inconsistent results. The main problem is if the Borg class is
instantiated outside a containing class, then I need to go up a
different number of stack frames. But this information isn't
available till after I've run out of stack frames.

Hopefully the following code better describes what I'm looking to do.

import sys

class Borg:
_shared_state = {}
def __init__(self):
self.__dict__=self._shared_state

class Assimilated(Borg):
valueByCaller = {}

def __init__(self, setupvalue):
print "In Assimilated.__init__()"
print "setupvalue is: " + str(setupvalue)

# would like key to be name of class (or module) that
# contins Assimilated
callerID = sys._getframe(1).f_code.co_name

self.valueByCaller[callerID] = setupvalue

print self.valueByCaller

def action(self, calledvalue):
print "In Assimilated.action()"
print "self.__classname__: " + self.__class__.__name__
print "calledvalue is: " + str(calledvalue)

print "self.valueByCaller"
print self.valueByCaller

# need to get proper key depending on which class (or module)
# made the call
# print "0: " + sys._getframe(0).f_code.co_name
# print "1: " + sys._getframe(1).f_code.co_name
# print "2: " + sys._getframe(2).f_code.co_name
# print "3: " + sys._getframe(3).f_code.co_name
callerID = sys._getframe(2).f_code.co_name
print "callerID"
print callerID

if(self.valueByCaller[callerID] <= calledvalue):
print "doing the action"
class A:
assim_object = Assimilated(2)

def __init__(self):
self.assim_object.action(2)
self.assim_object.action(3)

class B:
assim_object = Assimilated(3)

def __init__(self):
self.assim_object.action(3)
self.assim_object.action(4)

class C:
assim_object = Assimilated(4)

def __init__(self):
self.assim_object.action(4)
self.assim_object.action(5)
a=A()
b=B()
c=C()

obj=Assimilated(3)
#obj.action(3)
When I run this, I get the following output:

In Assimilated.__init__()
setupvalue is: 2
{'A': 2}
In Assimilated.__init__()
setupvalue is: 3
{'A': 2, 'B': 3}
In Assimilated.__init__()
setupvalue is: 4
{'A': 2, 'C': 4, 'B': 3}
In Assimilated.action()
self.__classname__: Assimilated
calledvalue is: 2
self.valueByCaller
{'A': 2, 'C': 4, 'B': 3}
callerID
<module>
Traceback (most recent call last):
File "\CallerID.py", line 67, in <module>
a=A()
File "\CallerID.py", line 49, in __init__
self.assim_object.action(2)
File "\CallerID.py", line 41, in action
if(self.valueByCaller[callerID] <= calledvalue):
KeyError: '<module>'

What I found most peculiar when I started this was that the
valueByCaller dictionary was completely populated before the __init__
method of a was executed. I'm pretty sure that this has to do with
the difference between when the object gets instanced and when it gets
initialized, but I need to do some more research and reading to be
able to explain it to myself.

Thanks for any help you can give me.

Kevin
Sep 8 '08 #1
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1 Reply


P: n/a
seanacais a crit :
I want to create a class derived from a Borg class that can
instantiated as part of a script or be contained in other classes.
When methods from the Borg class are called, I would like to know the
name of the class that contains the Borg class.
I've played a bit with inspect and _getframe from the sys module but
get inconsistent results. The main problem is if the Borg class is
instantiated outside a containing class, then I need to go up a
different number of stack frames. But this information isn't
available till after I've run out of stack frames.
The simplest solution is usually the better : explicitely pass the
caller (whether instance or module or whatever you want)

Hopefully the following code better describes what I'm looking to do.

import sys

class Borg:
_shared_state = {}
def __init__(self):
self.__dict__=self._shared_state

class Assimilated(Borg):
valueByCaller = {}
You understand that, being a class attribute, valueByCaller won't be
part of the Borg's _shared_state ?
def __init__(self, setupvalue):
print "In Assimilated.__init__()"
print "setupvalue is: " + str(setupvalue)

# would like key to be name of class (or module) that
# contins Assimilated
callerID = sys._getframe(1).f_code.co_name

self.valueByCaller[callerID] = setupvalue

print self.valueByCaller
Anyway, since you override __init__ and don't call Borg.__init__, your
Assimilated class doesn't behave as a Borg.

(snip)

>
When I run this, I get the following output:

In Assimilated.__init__()
setupvalue is: 2
{'A': 2}
In Assimilated.__init__()
setupvalue is: 3
{'A': 2, 'B': 3}
In Assimilated.__init__()
setupvalue is: 4
{'A': 2, 'C': 4, 'B': 3}
(snip)
>
What I found most peculiar when I started this was that the
valueByCaller dictionary was completely populated before the __init__
method of a was executed.
Indeed. In classes A, B and C, assim_object is class attribute - so it
is instanciated when the class statement is executed.
I'm pretty sure that this has to do with
the difference between when the object gets instanced and when it gets
initialized,
Not at all. It has to do with the fact that all statements within a
class block are executed before the class statement itself is executed.
And since your class statements are at the top-level, they are executed
when the module is initialised (that is, passed to the python runtime or
first imported).
but I need to do some more research and reading to be
able to explain it to myself.
Indeed. May I suggest that you *learn* Python's object model and
Python's execution model instead of assuming anything ? This will save
you a whole lot of time and frustration !-)
Sep 9 '08 #2

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