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

Eric Snow added the comment: I'd missed that unary + (new in 3.3). That's pretty cool. -- nosy: +eric.snow ___ Python tracker ___ ___

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

Raymond Hettinger added the comment: At its most basic, a Counter is simply a dictionary with a __missing__ method that supplies a default of zero. It is intentional that everything else behaves as much like a regular dictionary as possible. You're allowed to store *anything* in the dict val

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

Stephen Webber added the comment: Hmm, that is odd behavior indeed. I think having keys that point to zero values is important for iterating over a set. For example: >>> x = Counter(a=10, b=0) >>> for k in set(x): ... x[k] += 1 ... >>> x Counter({'a': 11, 'b': 1}) is probably preferable

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

Meador Inge added the comment: Ah, good examples Mark. So, why is it ever useful keep a key with a value of zero? In other words, why: >>> Counter(a=0) Counter({'a': 0}) instead of: >>> Counter(a=0) Counter() ? The latter seems more consistent to me. -- _

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

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) + Coun

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

Meador Inge added the comment: Raymond, Stephen's analysis seems correct. Are we missing something or can this issue be closed? -- nosy: +meador.inge ___ Python tracker ___ ___

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

Stephen Webber added the comment: This is intentional handling of non-existant variables, and is not resticted to '==' operations. Returning the value of a Counter parameter that has not yet been set returns 0 by default. See the documentation here: http://docs.python.org/library/collections.h

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

New submission from Raymond Hettinger : >>> from collections import Counter >>> x=Counter(a=10,b=0,c=3) >>> y=Counter(a=10,c=3) >>> x == y False >>> all(x[k]==y[k] for k in set(x) | set(y)) True -- assignee: rhettinger components: Library (Lib) messages: 154827 nosy: rhettinger priority: