Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
To: python-list@python.org
From: Peter Otten <__peter__@web.de>
Subject: Re: TypeError: unbound method add() must be called with BinaryTree instance as first argument (got nothing instead)
Date: Sat, 18 May 2013 21:24:46 +0200
Organization: None
References: <CAGGBd_q6AB8ARcotzu4QpS1N3BwKCOr=PGv6oUewsM=b-j=SEA@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7Bit
User-Agent: KNode/4.7.3
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.1814.1368905100.3114.python-list@python.org>
Lines: 77
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:45524

Dan Stromberg wrote:

> I'm getting the error in the subject, from the following code:
>     def add(self, key):
>         """
>         Adds a node containing I{key} to the subtree
>         rooted at I{self}, returning the added node.
>         """
>         node = self.find(key)
>         if not node:
>             node.key = key
>             # placeholder
>             node.left, node.right = self.__class__(parent=node),
> self.__class__(parent=node)
>             return (False, node)
>         else:
>             if random.random() < 0.5:
>                 print('node.left is %s' % node.left)
>                 return BinaryTree.add(self=node.left, key=key)
>             else:
>                 print('node.right is %s' % node.left)
>                 return BinaryTree.add(self=node.right, key=key)
> 
> The above add() method is part of a BinaryTree(object) class, whose
> subclass is RedBlackTree.
> 
> We need to explicitly call BinaryTree.add() with an explict self, to avoid
> inappropriately calling RedBlackTree.add().; BinaryTree.add() is being
> called with a RedBlackTree instance as self.
> 
> The debugging print and traceback look like:
> node.left is  0 -1 red
> Traceback (most recent call last):
>   File "app_main.py", line 51, in run_toplevel
>   File "test-red_black_tree_mod", line 328, in <module>
>     test()
>   File "test-red_black_tree_mod", line 316, in test
>     all_good &= test_duplicates()
>   File "test-red_black_tree_mod", line 194, in test_duplicates
>     tree.add(value)
>   File
> "/home/dstromberg/src/home-svn/red-black-tree-
mod/trunk/duncan/red_black_bag_mod.py",
> line 919, in add
>     (replaced, node) = super(RedBlackTree, self).add(key=key)
>   File
> "/home/dstromberg/src/home-svn/red-black-tree-
mod/trunk/duncan/red_black_bag_mod.py",
> line 376, in add
>     return BinaryTree.add(self=node.left, key=key)
> TypeError: unbound method add() must be called with BinaryTree instance as
> first argument (got nothing instead)
> 
> Why is it complaining that .add() is getting nothing, when node.left isn't
> None?  As you can see above the traceback, it's got a value represented by
> "node.left is  0 -1 red".
> 
> python 2.x, python 3.x and pypy all give this same error, though jython
> errors out at a different point in the same method.
> 
> Thanks!

I never ran into that, but apparently you cannot pass self as a keyword 
parameter:

>>> class A(object):
...     def add(self): pass
... 
>>> a = A()
>>> A.add(a)
>>> A.add(self=a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unbound method add() must be called with A instance as first 
argument (got nothing instead)