On 1/28/2019 11:14 AM, Roberto Martínez wrote: > Hi, >> the documentation about Special method lookup > <https://docs.python.org/3/reference/datamodel.html#special-method-lookup> > claims: > "For custom classes, implicit invocations of special methods are only > guaranteed to work correctly if defined on an object’s type, not in the > object’s instance dictionary. " >> Does this statement holds for every special method mentioned in section 3.3 > Special method names > <https://docs.python.org/3/reference/datamodel.html#special-method-names>? You should generally take such statements at face value. Unless you find specific exceptions mentioned elsewhere, 'no guarantee' means just that, regardless of how any particular implementation behaves today. -- Terry Jan Reedy