[Python-Dev] == on object tests identity in 3.x (original) (raw)

Andreas Maier andreas.r.maier at gmx.de
Tue Jul 8 02:12:14 CEST 2014

Am 2014-07-07 18:09, schrieb Ethan Furman:

Just because two instances from the same object have the same value does not mean they are equal. For a real-life example, look at twins: biologically identical, yet not equal.

I think they are equal in Python if they have the same value, by definition, because somewhere the Python docs state that equality compares the object's values.

The reality though is that value is more vague than equality test (as it was already pointed out in this thread): A class designer can directly implement what equality means to the class, but he or she cannot implement an accessor method for the value. The value plays a role only indirectly as part of equality and ordering tests.

Andy

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