Add nondestructive selection to sets

[ipatrol]

BPO	8830
Nosy	@ericvsmith, @ipatrol
Superseder	bpo-7212: Retrieve an arbitrary element from a set without removing it

^{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 2010-05-27.01:36:13.233>
created_at = <Date 2010-05-27.01:25:08.858>
labels = ['type-feature']
title = 'Add nondestructive selection to sets'
updated_at = <Date 2010-05-27.01:36:13.223>
user = 'https://github.com/ipatrol'

bugs.python.org fields:

activity = <Date 2010-05-27.01:36:13.223>
actor = 'eric.smith'
assignee = 'none'
closed = True
closed_date = <Date 2010-05-27.01:36:13.233>
closer = 'eric.smith'
components = ['None']
creation = <Date 2010-05-27.01:25:08.858>
creator = 'ipatrol'
dependencies = []
files = []
hgrepos = []
issue_num = 8830
keywords = []
message_count = 2.0
messages = ['106590', '106591']
nosy_count = 2.0
nosy_names = ['eric.smith', 'ipatrol']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = None
status = 'closed'
superseder = '7212'
type = 'enhancement'
url = 'https://bugs.python.org/issue8830'
versions = ['Python 2.7', 'Python 3.2']

[ipatrol]

I see in a lot of references for computer programming a function that returns an arbitrary value from a standard or frozen set. http://en.wikipedia.org/wiki/Set_%28computer_science%29 describes it as pick. It surprised me when I discovered that Python sets don't have this method. I would suggest the returned value be somewhat random to prevent repeated calls from returning repeated results. Perhaps a small C-level counter could control that, which can then roll over uneventfully if enough calls are made.

[ericvsmith]

This is a dupe of bpo-7212.