bool({}) should raise an exception, if we're being strict. You could try to define the addition of keys like you suggest, but you need to force a value type wh

bool({}) should raise an exception, if we're being strict. You could try to define the addition of keys like you suggest, but you need to force a value type which defines a + operation into the same type. Which is what Counter() does, below (appending strings). Python is dynamically typed, so you can't maintain these expectations. Therefore, summation and bool({}) should be an error, or merely "true" (ie, yes, it exists, and is not None) -- as per the original thread and resolution.