Working on closing out some bug reports at work, and I ran into one about comparisons to 'None' will result in elementwise object comparison in the future. Now, I totally get the idea behind the change, and I am not here to argue that decision. However, I have come across a situation where the change might have an unexpected negative consequence. Consider the following: p = Pool(min(len(tiles), maxprocs)) res = p.map(_wrap_tilesum, izip(repeat(args.varname), tiles, repeat(request_start), repeat(args.timeLen), repeat(args.srcdir), repeat(args.tarredInputs), repeat(args.dataset))) p.close() p.join() (tiles, tile_start_dates, tile_end_dates, tile_lons, tile_lats) = zip(*res) if None in tiles: logging.critical("At least one tile was invalid. Aborting") raise Exception("Invalid data retrieved!") Essentailly, in the nominal case, "tiles" would be a list of numpy arrays. However, my error handling is such that if one of my subprocesses errors out, then it returns a None instead of a numpy array. So, all I am doing is testing to see if any of the items in the "tiles" list is None. I have zero desire to actually compare None with the elements in the arrays that happens to be in the list. Of course, I can rewrite this if statement as `any(tile is None for tile in tiles)`, but that isn't my point. Is `if None in tiles:` an unreasonable idiom? Cheers! Ben Root