[issue12473] factory func of collections.defaultdict should receive the "missing key" as args when called.

[HaiYun Yan]

New submission from HaiYun Yan <lyricconch at gmail.com>:

for example:

def calc(params):
    """ i am factoring numbers. """
    # an expensive CPU cost function but 
    # passin params and return result are both lightweight

cachedcalc = collections.defaultdict(calc)
result = cachedcalc[0xFFFFFFFFFFFFFFFFFFF0AC0FFF1]

----------
components: Library (Lib)
messages: 139624
nosy: lyricconch
priority: normal
severity: normal
status: open
title: factory func of collections.defaultdict should receive the "missing key" as args when called.
type: behavior
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue12473>
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