Josh Rosenberg added the comment: You shouldn't presize when the input is a potentially non-unique iterable. It makes sense to presize for inputs of type dict or set, but for a list, the assumption is that many duplicates will be present, since deduping is a common use case for dicts (less so with the advent of sets, but still common enough to support without massive overallocation of memory).
In short, dict([(1, 2)] * 1000000) should not involve allocating GB of memory for the dict up front. ---------- nosy: +josh.r _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue23971> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
