[issue33385] setdefault() with a single argument doesn't work for dbm.gdbm and dmb.ndbm objects

[Raymond Hettinger]

Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:

Option 2 seems perfectly reasonable here as a way of preventing bugs (working, correct code wouldn't be using the existing default of None).

Option 1 is problematic because of the variance from Mutable Mapping, because breaking symmetry with get(), and because the change in behavior is implicit.

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nosy: +rhettinger

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33385>
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