What is a "method-wrapper" object?

Roy Smith roy at panix.com
Tue Sep 23 03:08:01 CEST 2003


I had a class called rule and a subclass of rule, called bgpRule, in a 
file called bgp.py.

I decided to move the rule class to its own file, called rule.py.  The 
original file did "import rule".  I forgot to change bgpRule's 
__init__() method from calling rule.__init__() to call 
rule.rule.__init__().

Amazingly, this caused no immediate error, but rule.__init__() never got 
called.  When I found the problem, I was puzzled as to why I didn't just 
get AttributeError when I called rule.__init__().  A little 
investigation led to this:

[rsmith at qwerky agent]$ py
Python 2.2.2 (#1, Apr  5 2003, 13:59:12) 
[GCC 3.2.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import rule
>>> dir (rule)
['__builtins__', '__doc__', '__file__', '__name__', 'rule', 'target', 
'time']
>>> print rule.__init__  
<method-wrapper object at 0x816c27c>
>>> print rule.__init__()
None
>>> 

So, what is this "method-wrapper" thingie that doesn't show up in the 
module's dir()?  I don't see any mention of it in the on-line 
documentation.  Have I stumbled upon one of those deep dark Python 
secrets that mere mortals aren't supposed to know about?




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