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POPython for loop not working on custom container
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copied!<p><strong>EDIT</strong>: I added <code>__iter__</code> to my Map class (i forgot it didn't inherit from Tree), but now the for loop returns "generator objects":</p> <pre><code><generator object _next at 0x82a4b94> Traceback (most recent call last): File "Map.py", line 43, in <module> print "First: %s, Second: %s" % (pair.first(), pair.second()) AttributeError: 'generator' object has no attribute 'first' </code></pre> <p>So there's an issue with my next function, right?</p> <hr> <p>For fun I created a RedBlack Tree in Python, and it's working properly. Now to copy the STL from C++ I'm creating a Map class to wrap the tree, for an alternative to the Python dict.</p> <p>The issue is when I try and loop through the Map, it's not working properly.</p> <pre><code>phonebook = Map() phonebook["Joe"] = "555-555-3422" phonebook["Rob"] = "231-523-2357" for pair in phonebook: print "First: %s, Second: %s" % (pair.first(), pair.second()) </code></pre> <p>The error that I get is:</p> <pre><code>Traceback (most recent call last): File "Map.py", line 38, in <module> for pair in phonebook: File "Map.py", line 19, in __getitem__ return self._tree.find(key) File "Python/Tree/SearchTree.py", line 82, in find raise TreeException('No node with key %s' % key) Tree.TreeException: 'No node with key 0' </code></pre> <p>I don't know why it's looking for key 0, when my keys are Strings. Using pdb I noticed that after the for loop starts, the first line executed is a call to <code>__getitem__</code> with key 0....</p> <p>Map is defined as:</p> <pre><code>class Map: def __init__(self): self._tree = RedBlackTree() def __getitem__(self, key): return self._tree.find(key) def __setitem__(self, key, item): self._tree.insert(Pair(key, item)) </code></pre> <p>From my understanding, I had to create an iterator for my tree, for this to work properly. I wasn't quite sure how to do this, so I looked around and combined a few approaches: (In my RedBlack tree implementation, NULL is an actual node)</p> <pre><code>class TreeIterator(): def __init__(self, root, size): self._current = root self._size = size self.num_visited = 0 def __iter__(self): return self def next(self): return self._next(self._current) def _next(self, curr): self.num_visited = self.num_visited + 1 if self.num_visited == self._size: raise StopIteration if curr.left is not None and curr.left is not TreeNode.NULL: for node in _next(curr.left): yield node yield curr if curr.right is not None and curr.right is not TreeNode.NULL: for node in _next(curr.right): yield node </code></pre> <p>and in my SearchTree superclass:</p> <pre><code>def __iter__(self): return TreeIterator(self.root, self.size) </code></pre> <p>What am I doing wrong?</p>

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