As expected (considering the link to dict ordering here), the inconsistent results are tied to hash randomization: $ for i in `seq 1 25`; do echo $i; PYTHONHASHSEED=$i ./python /tmp/odict_reproduce.py; done 1 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1794, in <module> od.popitem(last=False) KeyError: ('https', 'ml.wikipedia.org', 443) 2 3 4 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1737, in <module> od.popitem(last=False) KeyError: ('https', 'li.wikipedia.org', 443) 5 6 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1699, in <module> od.popitem(last=False) KeyError: ('https', 'ksh.wikipedia.org', 443) 7 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1889, in <module> od.popitem(last=False) KeyError: ('https', 'nds-nl.wikipedia.org', 443) 8 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1794, in <module> od.popitem(last=False) KeyError: ('https', 'ml.wikipedia.org', 443) 9 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1528, in <module> od.popitem(last=False) KeyError: ('https', 'ga.wikipedia.org', 443) 10 11 12 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1585, in <module> od.popitem(last=False) KeyError: ('https', 'hu.wikipedia.org', 443) 13 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1737, in <module> od.popitem(last=False) KeyError: ('https', 'li.wikipedia.org', 443) 14 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1775, in <module> od.popitem(last=False) KeyError: ('https', 'mg.wikipedia.org', 443) 15 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1965, in <module> od.popitem(last=False) KeyError: ('https', 'pdc.wikipedia.org', 443) 16 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1680, in <module> od.popitem(last=False) KeyError: ('https', 'it.wikipedia.org', 443) 17 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1452, in <module> od.popitem(last=False) KeyError: ('https', 'fa.wikipedia.org', 443) 18 19 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1965, in <module> od.popitem(last=False) KeyError: ('https', 'nn.wikipedia.org', 443) 20 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1642, in <module> od.popitem(last=False) KeyError: ('https', 'ilo.wikipedia.org', 443) 21 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1319, in <module> od.popitem(last=False) KeyError: ('https', 'da.wikipedia.org', 443) 22 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1661, in <module> od.popitem(last=False) KeyError: ('https', 'it.wikipedia.org', 443) 23 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1547, in <module> od.popitem(last=False) KeyError: ('https', 'gl.wikipedia.org', 443) 24 25 Traceback (most recent call last): File "/tmp/odict_reproduce.py", line 1699, in <module> od.popitem(last=False) KeyError: ('https', 'ksh.wikipedia.org', 443)