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GeezerVison is showing github.com — factory func of collections.defaultdict should receive the "missing key" as args when called. · Issue #56682 · python/cpython

factory func of collections.defaultdict should receive the "missing key" as args when called. #56682

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factory func of collections.defaultdict should receive the "missing key" as args when called.#56682
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stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directorytype-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Description

lyricconch
mannequin
opened on Jul 2, 2011
Issue body actions
BPO 12473
Nosy @amauryfa

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 2011-07-02.08:31:11.474>
created_at = <Date 2011-07-02.07:21:09.476>
labels = ['invalid', 'type-bug', 'library']
title = 'factory func of collections.defaultdict should receive the "missing key" as args when called.'
updated_at = <Date 2011-07-02.08:31:11.467>
user = 'https://bugs.python.org/lyricconch'

bugs.python.org fields:

activity = <Date 2011-07-02.08:31:11.467>
actor = 'amaury.forgeotdarc'
assignee = 'none'
closed = True
closed_date = <Date 2011-07-02.08:31:11.474>
closer = 'amaury.forgeotdarc'
components = ['Library (Lib)']
creation = <Date 2011-07-02.07:21:09.476>
creator = 'lyricconch'
dependencies = []
files = []
hgrepos = []
issue_num = 12473
keywords = []
message_count = 2.0
messages = ['139624', '139625']
nosy_count = 2.0
nosy_names = ['amaury.forgeotdarc', 'lyricconch']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue12473'
versions = ['Python 2.7']

Activity

  1. lyricconch commented on Jul 2, 2011

    @lyricconch
    lyricconchmannequin
    on Jul 2, 2011
    MannequinAuthor
    More actions
    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]
  2. lyricconch
    added
    stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory
    type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error
    on Jul 2, 2011

  3. amauryfa commented on Jul 2, 2011

    @amauryfa
    amauryfa
    on Jul 2, 2011
    Contributor
    More actions

    -1. Besides compatibility issues, defaultdict is a dict: it contains data, and is not meant to consume CPU when accessing items. Its "default" function should return initial values, like 0 or an empty list.

    I think what you want is "memoization"; a memoized function still looks like a function! there are many implementations for python, one of these is here: http://wiki.python.org/moin/PythonDecoratorLibrary#Memoize

  4. amauryfa
    closed this as completedon Jul 2, 2011
  5. amauryfa
    added
    invalid
    on Jul 2, 2011
  6. ezio-melotti
    transferred this issue fromon Apr 10, 2022
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    stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directorytype-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

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