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POPython: hash defined on class won't recognise tuple
 

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  1. POPython: hash defined on class won't recognise tuple
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    <p>I am trying to implement the hash definition suggested <a href="https://stackoverflow.com/questions/2909106/python-whats-a-correct-and-good-way-to-implement-hash">here</a> but I am getting an error when trying to use hash on the class. The class is defined as so:</p> <pre><code>class Metabolite: def __init__(self, name_in='', id_in='', synonyms_in=[], InChIKey_in='', formulae_in=[], charge_in='', ecs_in=[], mtk_in = [], mtb_in = '', mtm_in = '', mts_in = '', bkm_id_in = '', source_in = ''): self.name = name_in self.id = id_in self.formulae = formulae_in self.inchikey = InChIKey_in self.synonyms = synonyms_in self.charge = charge_in self.ecs = ecs_in self.mtb = mtb_in self.mtk = mtk_in self.mtm = mtm_in self.mts = mts_in self.bkm_id = bkm_id_in self.source = source_in def key(self): return self.id, self.inchikey, self.mts, self.mtk, self.mtb, self.mtk def __key(self): return tuple([self.id, self.inchikey, self.mts, self.mtk, self.mtb, self.mtk]) def __eq__(self, other): return self.__key() == other.__key() def __hash__(self): return hash(tuple(self.__key())) </code></pre> <p>However on creating an instance of this class and asking for a hash I get the following:</p> <pre><code>&gt;&gt;&gt; met = Metabolite('this_metabolite', '10002', 'AADBRHFDG') &gt;&gt;&gt; hash(met) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) &lt;ipython-input-8-7941e6f25128&gt; in &lt;module&gt;() ----&gt; 1 hash(met) classes.py in __hash__(self) 27 28 def __hash__(self): ---&gt; 29 return hash(tuple(self.__key())) 30 31 TypeError: unhashable type: 'list' </code></pre> <p>despite my desperate attempts in the class definition to force the type to be a (hashable) tuple. I am new to classes in Python, any help would be greatly appreciated.</p> <p>When run in IDLE, the error comes up as:</p> <pre><code>Traceback (most recent call last): File "&lt;pyshell#3&gt;", line 1, in &lt;module&gt; hash(met) File "&lt;string&gt;", line 27, in __hash__ TypeError: unhashable type: 'list' </code></pre> <p>SOLVED: thanks to those who responded.</p> <p>A tuple containing an empty list will not work:</p> <pre><code>&gt;&gt;&gt; my_tuple = tuple(('a',[])) &gt;&gt;&gt; type(my_tuple) tuple &gt;&gt;&gt; hash(my_tuple) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) &lt;ipython-input-28-f63af41cc75b&gt; in &lt;module&gt;() ----&gt; 1 hash(my_tuple) TypeError: unhashable type: 'list' </code></pre> <p>so I had to create a list of my variables before returning them in <code>__key()</code>:</p> <pre><code>def __key(self): key_list = [] key_list.append(self.id) key_list.append(self.inchikey) key_list.append(self.mts) key_list.append(self.mtb) for entry in self.mtk: key_list.append(entry) return tuple(key_list) </code></pre>
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    1. USCommunity
    1. USWill Bryant
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    1. COI just ran your class in idle, and I don't get this error. Instead, I get 301521507 as a result.
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      1. POPython: hash defined on class won't recognise tuple
      1. USπόδας ὠκύς
    2. COI didn't get an error either, what version of python are you running?
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      1. USHoopdady
    3. COSame here, no errors, check your code without IPython, it is known for its side-effects.
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      1. USRostyslav Dzinko
 

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