mutlifile inheritance problem
Ned Batchelder
ned at nedbatchelder.com
Wed Sep 18 20:38:10 EDT 2013
On 9/18/13 7:54 PM, Peter Cacioppi wrote:
> This is a very old topic, but here is a trick for single inheritance. (The problem you allude to isn't restricted to multiple inheritance).
>
> Any class with a single parent simply defines this function.
>
>
> def mySuper(self) :
> return super(self.__class__, self)
>
> And then any parent function be referenced like
> self.mySuper().foo()
You can't use self.__class__ for super, it won't give you the right
class if you are using subclasses:
class MyBase(object):
def mySuper(self):
return super(self.__class__, self)
def say(self):
print "This is MyBase!"
class Thing(MyBase):
def say_it(self):
print "The parent:"
self.mySuper().say()
def say(self):
print "this is Thing!"
class SubThing(Thing):
pass
thing = Thing()
thing.say_it()
sub = SubThing()
sub.say_it()
This produces:
The parent:
This is MyBase!
The parent:
this is Thing!
super() takes a class and an instance for a reason. If you could use
self.__class__ for the class, then it would only take the instance.
Super() needs to know the instance, but also needs to know the class
it's being called from.
--Ned.
> This includes __init__.
>
> You can read more here.
>
> http://atlee.ca/blog/posts/blog20081121python-reload-danger-here-be-dragons.html
>
>
> On Thursday, March 21, 2002 2:03:23 PM UTC-7, Marc wrote:
>> I have classes defined in different files and would like to inherit
>> from a class in file A.py for a class in file B.py but am running into
>> problems. I'm using Python 1.5.2 on Windows NT
>>
>> Here's a specific example:
>>
>> ************************
>> file cbase01.py:
>>
>> class CBase:
>>
>> def __init__(self):
>> self.cclass = None
>> print "cbase"
>>
>> class CImStream(CBase):
>>
>> def __init(self):
>> CBase.__init__(self)
>> print "CImStream"
>>
>> *************************
>> in file wrappers_A01.py:
>>
>> import cbase01
>> reload(cbase01)
>>
>> class ImStream_SavedBitmaps(cbase01.CImStream):
>>
>> def __init__(self):
>> cbase.CImStream.__init__(self)
>> print "SavedBitmaps"
>>
>> **************************
>> in file sequencer01.py
>>
>> import cbase01 # the offending lines, program works
>> reload(cbase01) # if I comment these out.
>>
>> class Sequencer:
>>
>> def Append(self, item):
>> pass
>>
>> *****************************
>> in test02.py
>>
>> import wrappers_A01
>> reload(wrappers_A01)
>>
>> import sequencer01
>> reload(sequencer01)
>>
>> x0 = wrappers_A01.ImStream_SavedBitmaps()
>> ***************************************************************
>>
>> If I run test02 I get the traceback
>>
>> Traceback (innermost last):
>> File "<string>", line 1, in ?
>> File "D:\PythonCode\pna\eyeTracking\tests\test02.py", line 15, in ?
>> x0 = wrappers_A01.ImStream_SavedBitmaps()
>> File "D:\PythonCode\pna\eyeTracking\tests\wrappers_A01.py", line 21,
>> in __init__
>> cbase.CImStream.__init__(self)
>> TypeError: unbound method must be called with class instance 1st
>> argument
>>
>>
>> Any ideas what I am doing wrong?
>>
>> Thanks,
>> Marc
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