Set Intersection returns unexpected results

[AfifElghraoui]

BPO	17875
Nosy	@mdickinson
Files	lists.dat: test_lists

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2013-04-30.07:04:29.680>
created_at = <Date 2013-04-30.05:04:30.602>
labels = ['interpreter-core', 'type-bug', 'invalid']
title = 'Set Intersection returns unexpected results'
updated_at = <Date 2013-04-30.07:04:29.678>
user = 'https://bugs.python.org/AfifElghraoui'

bugs.python.org fields:

activity = <Date 2013-04-30.07:04:29.678>
actor = 'mark.dickinson'
assignee = 'none'
closed = True
closed_date = <Date 2013-04-30.07:04:29.680>
closer = 'mark.dickinson'
components = ['Interpreter Core']
creation = <Date 2013-04-30.05:04:30.602>
creator = 'Afif.Elghraoui'
dependencies = []
files = ['30075']
hgrepos = []
issue_num = 17875
keywords = []
message_count = 2.0
messages = ['188125', '188132']
nosy_count = 2.0
nosy_names = ['mark.dickinson', 'Afif.Elghraoui']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue17875'
versions = ['Python 2.7']

[AfifElghraoui]

I have two lists of strings (gene identifiers) that I know have something in common. I convert them to lists and do an intersection and I get the empty set. As an example test case, I know they both have the string 'Rv0500'

>>> list1.index('Rv0500')
278
>>> list2.index('Rv0500')
245
>>> set(list1).intersection(set(list2))
set([])

I was expecting to get a few hundred matches. My two lists are attached to this report. This is how I created the data file:

>> x = shelve.open('lists.dat')
>> x['list1'] = list1
>> x['list2'] = list2
>> x.close()

I did my best to make this report complete-- thanks for all your help.

[mdickinson]

It appears that your list1 and list2 are not regular Python lists, but have type cobra.core.DictList (which inherits from list, but overrides the 'index' method). cobra is a 3rd party package, not maintained by the Python developers, so I'm afraid this isn't the right place to ask about it; is there a mailing list for the cobra package?