Readibility of ABCMeta._dump_registry()

[yahya-abou-imran]

BPO	32473
Nosy	@methane, @ilevkivskyi, @yahya-abou-imran
PRs	bpo-32473: Improve ABCMeta._dump_registry() readability #5091 [3.6] bpo-32473: Improve ABCMeta._dump_registry() readability (GH-5091) #5163

^{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 2018-01-12.10:48:15.601>
created_at = <Date 2018-01-01.06:09:25.865>
labels = ['type-feature', '3.7']
title = 'Readibility of ABCMeta._dump_registry()'
updated_at = <Date 2018-01-12.10:48:15.600>
user = 'https://github.com/yahya-abou-imran'

bugs.python.org fields:

activity = <Date 2018-01-12.10:48:15.600>
actor = 'methane'
assignee = 'none'
closed = True
closed_date = <Date 2018-01-12.10:48:15.601>
closer = 'methane'
components = []
creation = <Date 2018-01-01.06:09:25.865>
creator = 'yahya-abou-imran'
dependencies = []
files = []
hgrepos = []
issue_num = 32473
keywords = ['patch']
message_count = 3.0
messages = ['309321', '309840', '309847']
nosy_count = 3.0
nosy_names = ['methane', 'levkivskyi', 'yahya-abou-imran']
pr_nums = ['5091', '5163']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue32473'
versions = ['Python 3.6', 'Python 3.7']

[yahya-abou-imran]

From python-ideas:
https://mail.python.org/pipermail/python-ideas/2017-December/048504.html

In python 2.7, ABCs's caches and registries are sets. But in python 3.6 they are WeakSet.
In consequence, the output of _dump_registry() is almost useless:

>>> from collections import abc
>>> abc.Iterator._dump_registry()
Class: collections.abc.Iterator
Inv.counter: 40
_abc_cache: <_weakrefset.WeakSet object at 0x7f4b58fe2668>
_abc_negative_cache: <_weakrefset.WeakSet object at 0x7f4b53283780>
_abc_negative_cache_version: 40
_abc_registry: <_weakrefset.WeakSet object at 0x7f4b58fe2630>

We could convert them into a regular set before printing:

if isinstance(value, WeakSet):
    value = set(value)

The result:

>>> abc.Iterator._dump_registry()
Class: collections.abc.Iterator
Inv.counter: 40
_abc_cache: {<class 'dict_valueiterator'>, <class 'bytearray_iterator'>, <class 'tuple_iterator'>, <class 'dict_itemiterator'>, <class 'dict_keyiterator'>, <class 'str_iterator'>, <class 'zip'>, <class 'set_iterator'>, <class 'list_reverseiterator'>, <class 'range_iterator'>, <class 'longrange_iterator'>, <class 'list_iterator'>, <class 'bytes_iterator'>}
_abc_negative_cache: set()
_abc_negative_cache_version: 40
_abc_registry: set()

[methane]

New changeset ae12f5d by INADA Naoki (yahya-abou-imran) in branch 'master':
bpo-32473: Improve ABCMeta._dump_registry() readability (GH-5091)
ae12f5d

[methane]

New changeset a91662a by INADA Naoki (Miss Islington (bot)) in branch '3.6':
bpo-32473: Improve ABCMeta._dump_registry() readability (GH-5091)
a91662a