On 2014-06-18 18:37, Steven D'Aprano wrote:
Python tries very hard to ensure that every module is loaded only once.
(There are circumstances where you can fool it, but they're rare.)
Since
the module holds state (variables) and behaviour (functions), modules
perform the same sort of role as classes, so a module which is loaded
once is very similar to a singleton instance. In other words, if you
want a class to implement singleton behaviour, you have to work at it.
But if you shift the functionality from the class into a module, Python
gives you singleton behaviour for free.
But if you're not sure why anyone would want a singleton instance, I
agree with you: most (but not all) uses of singletons are unnecessary.
The idea of a singleton class is new to me as is this comparison of
class vs module.
Can anyone suggest a place to turn for more discussion of the topic?
thks, alexK
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