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add a cell construtor, and expose the cell type in Lib/types.py #80092

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pierreglaser mannequin opened this issue Feb 6, 2019 · 3 comments
Closed

add a cell construtor, and expose the cell type in Lib/types.py #80092

pierreglaser mannequin opened this issue Feb 6, 2019 · 3 comments
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3.8 only security fixes type-feature A feature request or enhancement

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@pierreglaser
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Mannequin

pierreglaser mannequin commented Feb 6, 2019

BPO 35911
Nosy @pitrou, @serhiy-storchaka, @1st1, @pierreglaser
PRs
  • bpo-35911: add cell constructor #11771
  • bpo-35911: add cell constructor #11771
    		•
    Files
  • cell.patch
  • test_cell.py
    		•

    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 2019-02-07.19:37:16.139>
created_at = <Date 2019-02-06.10:55:47.309>
labels = ['type-feature', '3.8']
title = 'add a cell construtor, and expose the cell type in Lib/types.py'
updated_at = <Date 2019-02-07.19:37:16.138>
user = 'https://github.com/pierreglaser'

    bugs.python.org fields:

    activity = <Date 2019-02-07.19:37:16.138>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2019-02-07.19:37:16.139>
closer = 'pitrou'
components = []
creation = <Date 2019-02-06.10:55:47.309>
creator = 'pierreglaser'
dependencies = []
files = ['48105', '48106']
hgrepos = []
issue_num = 35911
keywords = ['patch']
message_count = 3.0
messages = ['334924', '334931', '335037']
nosy_count = 4.0
nosy_names = ['pitrou', 'serhiy.storchaka', 'yselivanov', 'pierreglaser']
pr_nums = ['11771', '11771']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue35911'
versions = ['Python 3.8']
    @pierreglaser
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    pierreglaser mannequin commented Feb 6, 2019

    cell objects are containers for the free variables of functions defined in a
    local scope. They are located in a function's __closure__ attribute (when
    it is not None). A cell is a very simple object, with a single (optional, e.g
    the cell can be empty) attribute: cell_contents.

    The C/Python API provides a constructor to create such objects (PyCell_New).
    However no cell.__new__ method is exposed to the pure python user. Workarounds
    exist, but are hacky, and involve the creation of intermediate, unused
    functions.

    Why would cell-creation be useful? because creating cells happens in pickle
    extensions modules designed to save user-defined functions and classes
    (https://github.com/cloudpipe/cloudpickle) (*). These moudules are dependencies of
    many widely-used data science frameworks (pyspark, ray, dask). Exposing a cell
    constructor will simplify theses extensions code base, and alleviate their
    maintenance cost.

    I propose to add and expose a simple cell constructor, that accepts 0 (empty
    cells) or 1 arguments. I also propose to expose the cell type in Lib/types.py
    (as types.CellType)

    (*): see related issues: https://bugs.python.org/issue35900

    @pierreglaser pierreglaser mannequin added 3.8 only security fixes type-feature A feature request or enhancement labels Feb 6, 2019
    @pitrou
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    pitrou commented Feb 6, 2019

    Hi Pierre,

    You'll want to submit your patch as a GitHub pull request.
    Also your PR will have to contain:

    • tests for the new Python-facing API
    • documentation for the new API

    You may want to read more in the developer's guide:
    https://devguide.python.org/

    @pitrou
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    pitrou commented Feb 7, 2019

    New changeset df8d2cd by Antoine Pitrou (Pierre Glaser) in branch 'master':
    bpo-35911: add cell constructor (GH-11771)
    df8d2cd

    @pitrou pitrou closed this as completed Feb 7, 2019
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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