[issue16613] ChainMap.new_child could use improvement
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- assignee: - rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Raymond Hettinger added the comment: Can you write-up a patch with tests and a doc change? -- stage: - needs patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Changes by Vinay Sajip vinay_sa...@yahoo.co.uk: -- hgrepos: +171 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Changes by Vinay Sajip vinay_sa...@yahoo.co.uk: -- keywords: +patch Added file: http://bugs.python.org/file28694/951243de359a.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Vinay Sajip added the comment: Can you write-up a patch with tests and a doc change? Done. -- stage: needs patch - patch review ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Raymond Hettinger added the comment: Put a *versionchanged* tag in the doc entry and this is ready to apply. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- assignee: rhettinger - vinay.sajip ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Raymond Hettinger added the comment: Also, please change the variable name from *amap* to either *m* or *mapping*. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Roundup Robot added the comment: New changeset c0ddae67f4df by Vinay Sajip in branch 'default': Closes #16613: Added optional mapping argument to ChainMap.new_child. http://hg.python.org/cpython/rev/c0ddae67f4df -- nosy: +python-dev resolution: - fixed stage: patch review - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
Walter Dörwald added the comment:
I'd like to have this feature too. However the code should use
d if d is not None else {}
instead of
d or {}
For example I might want to use a subclass of dict (lowerdict) that converts
all keys to lowercase. When I use an empty lowerdict in new_child(),
new_child() would silently use a normal dict instead:
class lowerdict(dict):
def __getitem__(self, key):
return dict.__getitem__(
self,
key.lower() if isinstance(key, str) else key
)
import collections
cm = collections.ChainMap(lowerdict(), lowerdict())
cm2 = cm.new_child(lowerdict())
print(type(cm2.maps[0]))
This would print class 'dict'.
--
nosy: +doerwalter
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[issue16613] ChainMap.new_child could use improvement
Vinay Sajip added the comment:
d if d is not None else {}
Your intention makes sense, though I would prefer to write it as:
if d is None:
d = {}
return self.__class__(d, *self.maps)
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[issue16613] ChainMap.new_child could use improvement
R. David Murray added the comment: I agree that this would be useful. -- nosy: +r.david.murray ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16613 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16613] ChainMap.new_child could use improvement
New submission from Vinay Sajip:
ChainMap.new_child could IMO be improved through allowing an optional dict to
be passed, which is used to create the child. The use case is that you
sometimes need to temporarily push a new non-empty mapping in front of an
existing chain. This could be achieved by changing new_child to the following,
which is backwards-compatible:
def new_child(self, d=None):
'New ChainMap with a new dict followed by all previous maps.'
return self.__class__(d or {}, *self.maps)
--
components: Library (Lib)
messages: 176974
nosy: rhettinger, vinay.sajip
priority: normal
severity: normal
status: open
title: ChainMap.new_child could use improvement
type: enhancement
versions: Python 3.4
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