[Python-Dev] UserDict in 2.7 (original) (raw)

Raymond Hettinger raymond.hettinger at gmail.com
Tue Jun 22 18:24:42 CEST 2010

On Jun 22, 2010, at 5:48 AM, Benjamin Peterson wrote:

2010/6/22 Raymond Hettinger <raymond.hettinger at gmail.com>:

There's an entry in whatsnew for 2.7 to the effect of "The UserDict class is now a new-style class". I had thought there was a conscious decision to not change any existing classes from old-style to new-style. IIRC, Martin had championed this idea and had rejected all of proposals to make existing classes inherit from object. IIRC this was because UserDict tries to be a MutableMapping but abcs require new style classes.

ISTM, this change should be reverted to the way it was in 2.6.

The registration was already working fine:

Python 2.6.4 (r264:75821M, Oct 27 2009, 19:48:32) [GCC 4.0.1 (Apple Inc. build 5493)] on darwin

import UserDict import collections collections.MutableMapping.register(UserDict.UserDict) issubclass(UserDict.UserDict, collections.MutableMapping) True

We've didn't have any problems with this registration nor did there seem to be an issue with UserDict not implementing dictviews.

Please revert this change. UserDicts have a long history and are used by a lot of code, so we need to avoid unnecessary breakage.

Thank you,

Raymond

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