Steven D'Aprano wrote: > On Mon, 20 Apr 2009 15:13:15 -0500, Grant Edwards wrote: > > >> I fail to see the difference between "length greater than 0" and "list >> is not empty". They are, by definition, the same thing, aren't they? > > For built-in lists, but not necessarily for arbitrary list-like sequences. > > There's also the performance issue. I might have a sequence-like > structure where calling len() takes O(N**2) time, (say, a graph) but > calling __nozero__ might be O(1). Why defeat the class designer's > optimizations? Is that true? Calling len() actually traverses the whole list? > >
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