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PORedirect calls to a member of a class in python
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  1. PORedirect calls to a member of a class in python
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    copied!<p>I was trying to 'extend' a closed class</p> <pre><code>collections.defaultdict(lambda: 1) </code></pre> <p>by addint it 2 methods, called 'vocabulary', and 'wordcount' apparently it's impossible to setattr method to builin types, nor can I inherit from defaultdic, so I decided to write a class and redirect calls to it to the type I want to extend.</p> <pre><code>class BagOfWordDoc(): def __init__(self): self.data = collections.defaultdict(lambda: 1) for method in dir(self.data): if hasattr(getattr(self.data, method),'__call__') and method not in ['__class__', '__self__']: l = lambda *args: getattr(self.data, method)(*args) setattr(self, method,l) def vocabulary(self): return self.data.keys() def wordcount(self): return reduce(operator.add, self.data.values(), 0) </code></pre> <p>However it shows upon accessing it</p> <pre><code> doc = BagOfWordDoc() doc[123] = 123 # yields TypeError: values() takes no arguments (1 given) doc.keys() # yields TypeError: values() takes no arguments (1 given) doc.xxx() # yields TypeError: values() takes no arguments (1 given) </code></pre> <p>So it'is as if every lambda was mapped to the 'values' function And 'values' is the last element of the property list</p> <p>Do you know why this happens ? As for the initial problem, I am now thinking of rewriting my own defaultdict.</p> <h2>update</h2> <p>Based on the suggestion made, hereis the working implementation :</p> <pre><code>class BagOfWordDoc(): def __init__(self): self.data = collections.defaultdict(lambda: 0) def __getattr__(self, *args): return self.data.__getattribute__(*args) def vocabulary(self): return self.data.keys() def wordcount(self): return reduce(operator.add, self.data.values(), 0) </code></pre>
 

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