[issue2144] os.environ should inherit dict

[Raymond Hettinger]

Raymond Hettinger added the comment:

The builtins make direct calls to their own internal methods.  This has 
existed for a long time. It would be hard to change without crushing 
performance. Changing it violates Meyer's open-closed principle. And 
changing it also introduces weird, unexpected behaviors (i.e. a 
seemingly innocent method override can break pickling for an object -- 
we had a bug report on this once for dicts and sets).  Also, making 
these kind of changes makes it *much* harder for a builtin to guarantee 
that it invariants are maintained and opening the door for segfaults.

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nosy: +rhettinger

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