Python Set Comprehensions

Question

I'm just starting out learning python set comprehensions. Why does { 2**x for x in {0,1,2,3,4} } return {8, 1, 2, 4, 16} instead of the ordered {1, 2, 4, 8, 16}?

Python sets are not ordered; there's no "instead of", since those are the same set. — Wooble, Jul 17 '13 at 12:06
And of [python set changes element order?](http://stackoverflow.com/q/9792664) and [Set Comprehension in python](http://stackoverflow.com/a/17446318) — Martijn Pieters, Jul 17 '13 at 12:20
I think this has been updated in python 3 to be ordered more often — Brendan Metcalfe, Jun 07 '20 at 18:31

score 3 · Accepted Answer · answered Jul 17 '13 at 12:15

Mathematically speaking, sets do not have an order. When displaying or iterating over a set, Python obviously needs to provide a particular order, but this order is arbitrary and not to be relied on. The order is, however, fixed for a particular set; iterating over the same, unmodified set will produce the same order each time.

Python Set Comprehensions

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