[issue14182] collections.Counter equality test thrown-off by zero counts

[Mark Dickinson]

Mark Dickinson added the comment:

> Raymond, Stephen's analysis seems correct.  Are we missing something or
> can this issue be closed?

Well, depending on how you think about Counters, the current behaviour of equality definitely leads to some surprises.  For example:

>>> Counter(a = 3) + Counter(b = 0) == Counter(a = 3, b = 0)
False

OTOH, if we're consistent about regarding a count of 0 as 'equivalent' to a missing element, then __nonzero__ / __bool__ probably needs changing, too.

>>> c = Counter(a = 0)
>>> bool(c)
True
>>> bool(c + c)
False

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nosy: +mark.dickinson

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<http://bugs.python.org/issue14182>
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