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typing.NamedTuple() should prefix parameters with '_' #82372

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GlennGribble mannequin opened this issue Sep 16, 2019 · 9 comments
Closed

typing.NamedTuple() should prefix parameters with '_' #82372

GlennGribble mannequin opened this issue Sep 16, 2019 · 9 comments
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@serhiy-storchaka
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3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@GlennGribble
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GlennGribble mannequin commented Sep 16, 2019

BPO 38191
Nosy @gvanrossum, @serhiy-storchaka, @ilevkivskyi, @miss-islington, @Glenn Gribble
PRs
  • bpo-38191: Accept arbitrary keyword names in NamedTuple() and TypedDict(). #16222
  • [3.8] bpo-38191: Accept arbitrary keyword names in NamedTuple() and TypedDict(). (GH-16222) #16237
  • bpo-38191: Turn warnings into errors in NamedTuple() and TypedDict(). #16238
  • [3.7] bpo-38191: Accept arbitrary keyword names in NamedTuple(). (GH-16222) #16239
  • [3.8] bpo-38191: Use positional-only parameters in TypedDict(). #16240
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    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 = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2019-09-18.06:08:31.725>
created_at = <Date 2019-09-16.19:59:55.784>
labels = ['3.7', '3.8', 'type-feature', 'library', '3.9']
title = "typing.NamedTuple() should prefix parameters with '_'"
updated_at = <Date 2019-09-18.06:08:31.725>
user = 'https://github.com/GlennGribble'

    bugs.python.org fields:

    activity = <Date 2019-09-18.06:08:31.725>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2019-09-18.06:08:31.725>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2019-09-16.19:59:55.784>
creator = 'gribbg'
dependencies = []
files = []
hgrepos = []
issue_num = 38191
keywords = ['patch']
message_count = 9.0
messages = ['352579', '352620', '352622', '352654', '352655', '352656', '352657', '352659', '352697']
nosy_count = 5.0
nosy_names = ['gvanrossum', 'serhiy.storchaka', 'levkivskyi', 'miss-islington', 'gribbg']
pr_nums = ['16222', '16237', '16238', '16239', '16240']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38191'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']
    @GlennGribble
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    GlennGribble mannequin commented Sep 16, 2019 

    At present, it is not possible to use the shorthand notation to define a NamedTuple with typename or fields.  I.e., NamedTuple('MyTuple', typename=str, fields=int) does not work.  Changing the parameter names to _typename and _fields would allow any non-private, legal identifier to be used in the shorthand notation.
  
>>> import typing
>>> typing.NamedTuple('Example', fieldz=int)
<class '__main__.Example'>
>>> typing.NamedTuple('Example2', fields=int)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Program Files\Python37\lib\typing.py", line 1411, in __new__
    return _make_nmtuple(typename, fields)
  File "C:\Program Files\Python37\lib\typing.py", line 1326, in _make_nmtuple
    types = [(n, _type_check(t, msg)) for n, t in types]
TypeError: 'type' object is not iterable

    Of course, it is fairly easy to work around the issue by using fields parameter:

    >>> typing.NamedTuple('Example3', [('fields', int)])
<class '__main__.Example3'>

    There would be backwards compatibility issues with any code using named arguments for fields or typename.

    @GlennGribble GlennGribble mannequin added 3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir type-feature A feature request or enhancement labels Sep 16, 2019
    @serhiy-storchaka
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    Looks as a good case for positional-only parameters.

    But first passing these arguments by keyword should be deprecated.

    @serhiy-storchaka serhiy-storchaka self-assigned this Sep 17, 2019
    @serhiy-storchaka
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    PR 16222 adds support for arbitrary keyword argument names in NamedTuple and TypedDict. Passing arguments like "typename", "_typename", "fields" and "_fields" by keyword is still supported, but deprecated. I'm going to backport this to 3.8 and 3.7 (to 3.7 without deprecation warnings), and than convert warnings to error in master (by using positional-only parameters syntax).

    @serhiy-storchaka
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    New changeset 2bf31cc by Serhiy Storchaka in branch 'master':
    bpo-38191: Accept arbitrary keyword names in NamedTuple() and TypedDict(). (GH-16222)
    2bf31cc

    @miss-islington
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    New changeset 54ba5f1 by Miss Islington (bot) in branch '3.8':
    bpo-38191: Accept arbitrary keyword names in NamedTuple() and TypedDict(). (GH-16222)
    54ba5f1

    @serhiy-storchaka
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    Oh, when backported to 3.7 I have found that TypedDict is new in 3.8. So I think it is better to get rid of deprecations in TypedDict().

    @serhiy-storchaka
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    New changeset 69b3718 by Serhiy Storchaka in branch '3.7':
    [3.7] bpo-38191: Accept arbitrary keyword names in NamedTuple(). (GH-16222) (GH-16239)
    69b3718

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    New changeset 8fc5839 by Serhiy Storchaka in branch 'master':
    bpo-38191: Turn warnings into errors in NamedTuple() and TypedDict(). (GH-16238)
    8fc5839

    @serhiy-storchaka
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    New changeset 2adcd79 by Serhiy Storchaka in branch '3.8':
    bpo-38191: Use positional-only parameters in TypedDict(). (GH-16240)
    2adcd79

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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