Paolino wrote: > I thought rewriting __hash__ should be enough to avoid mutables problem > but: > > class H(set): > def __hash__(self) > return id(self) > > s=H() > > f=set() > > f.add(s) > f.remove(s) > > the add succeeds > the remove fails eventually not calling hash(s). Why don't you just use "frozenset"? -- Ciao, Matteo