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POExplanation needed regarding explanation of hashable objects
 

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    <p><a href="https://stackoverflow.com/users/5987/mark-ransom">Mark Ransom</a> answered on a <a href="https://stackoverflow.com/questions/2671376/hashable-immutable/2671476#2671476">SO question about hashes</a> here in SO:</p> <blockquote> <p>[...] An object is hashable if it has a hash value <strong>which never changes during its lifetime</strong>. So by the official definition, anything mutable can't be hashable, even if it has a <code>__hash__()</code> function. My statement about both requirements being necessary is untrue, because being hashable already implies the requirement to be immutable.</p> </blockquote> <p>I want to make sure, that I got that right - even as a non native speaker - so I hope someone corrects me if I got it wrong.</p> <p>Assuming this class</p> <pre><code>class Author(object): def __init__(self, id, name, age): self.id = id self.name = name self.age = age def __eq__(self, other): return self.id==other.id\ and self.name==other.name def __hash__(self): return hash(('id', self.id, 'name', self.name)) </code></pre> <p>I understand, that <code>__eq__</code> allows me to compare objects of this class with the <code>==</code> operator. From Marks answer I understand, that even if my object <code>peter = Author(1, "Peter", 33)</code> has a <code>__hash__</code> it is not hashable because I potentially could do something like <code>peter.age = 43</code> which means it is not immutable. So my objects of the class <code>Author</code> are not hashable and therefore not usable as keys in dictionarys for example? Did I get right or does it seem, that I need more explanation? :-)</p>
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