How to determine which method was used in an inheritance heirarchy?
Erik Jones
erik at myemma.com
Mon Jul 16 02:56:18 EDT 2007
On Jul 16, 2007, at 1:31 AM, Erik Jones wrote:
> On Jul 16, 2007, at 12:53 AM, Michele Simionato wrote:
>
>> On Jul 16, 7:18 am, Erik Jones <e... at myemma.com> wrote:
>>> On Jul 15, 2007, at 11:23 PM, Michele Simionato wrote:
>>>
>>>> On Jul 16, 5:51 am, Erik Jones <e... at myemma.com> wrote:
>>>>> Say you're given a call event frame for a method call. How can
>>>>> you
>>>>> tell if the code being executed came from a super class of the
>>>>> object
>>>>> or class the method was called on?
>>>
>>>>> Erik Jones
>>>
>>>> You look if the method was defined in self.__class__.__dict__.
>>>
>>>> Michele Simionato
>>>
>>> That doesn't seem to cover calling super class __init__ methods.
>>>
>>
>> I am probably missing something. In the following code the
>> method check_init checks if the current instance
>> possess an __init__ or if it just inherits one
>> from the ancestors. Is this what you want?
>>
>> class B(object):
>> def __init__(self):
>> 'something'
>> def check_init(self):
>> if '__init__' in self.__class__.__dict__:
>> print 'possesses __init__'
>> else:
>> print 'inherits __init__'
>>
>> class C(B):
>> 'something else'
>> def __init__(self):
>> print 'calling C.__init__'
>>
>> class D(B):
>> pass
>>
>> c = C()
>> d = D()
>>
>> c.check_init() #possesses __init__
>> d.check_init() #inherits __init__
>
> Ok, I see how I was pretty vague with my original questions.
> Given the pattern where you need to call a base class's constructor
> (or, other overriden method of the same name as that being called
> on the child class object):
>
> class A(object):
> def __init__(self):
> print self.__class__.__name__
>
> class B(A):
> def __init__(self):
> A.__init__(self)
> print self.__class__.__name__
>
> B()
>
> This will output:
>
> B
> B
>
> How can I get
>
> A
> B
Perhaps an even better example of what I'm trying to do would be in
order (this is minus any exception handling):
import sys
def mytrace(frame, event, arg):
if event == 'call':
func_name = frame.f_code.co_name
if func_name in frame.f_locals['self'].__class__.__dict__:
print frame.f_locals['self'].__class__.__name__
else:
for base in frame.f_locals['self'].__class__.__bases__:
if func_name in base.__dict__:
print base.__name__
break
class A(object):
def __init__(self):
pass
class B(A):
def __init__(self):
A.__init__(self)
sys.settrace(mytrace)
B()
This will output:
B
B
whereas I'm shooting for:
B
A
Erik Jones
Software Developer | Emma®
erik at myemma.com
800.595.4401 or 615.292.5888
615.292.0777 (fax)
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