problem with Python class creating

Bruno Desthuilliers bdesth.quelquechose at free.quelquepart.fr
Thu Oct 18 21:48:30 CEST 2007


dmitrey a écrit :
> Hi all,
> I have the code like this one:
> 
> from myMisc import ooIter
> class MyClass:

Unless you have a need for compatibility with aged Python versions, 
you'd be better using new-style classes:

class MyClass(object):

>     def __init__(self): pass

This is the default behaviour, so you may as well get rid of this line.

>     iterfcn = lambda *args: ooIter(self) # i.e pass the class instance
> to other func named ooIter

cf below about this...

>     field2 = val2
>     field3 = val3 # etc

You're aware that these two attributes are *class* attributes (that is, 
shared by all instances) ?

> So it yields "global name 'self' is not defined", that is true.

Indeed.

> How
> could I handle the situation?


     iterfcn = lambda self: ooIter(self)

which could as well be written:

     def iterfcn(self):
         ooIter(self)


Remember that Python's methods are - at least at this stage - plain 
functions, so the 'self' parameter is *not* optional - else how could 
the function access the current instance ?

And FWIW, you don't need the *args if you don't use any other than 'self'.

> Currently I do (and it works, but give me some troubles - I should
> call MyClass.__init__ for each children class,

Not unless these classes define their own initializers. But that's 
another problem

> and there are lots of
> those ones)
> 
> class MyClass:
>     def __init__(self):
>         iterfcn = lambda *args: ooIter(self) 

The real problem is that you create one anonymous function *per instance*.

> I suspect it has better solution, is it?

Indeed.



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