On 1/10/2010 11:23 AM, Eric Pavey wrote:
I should add (that as I understand it), when you do a 'from foo import blah', or 'from foo import *', this is doing a /copy/ (effectively) of that module's attributes into the current namespace. Doing "import foo" or "import foo as goo" is keeping a /reference /to the imported module rather than a copy.
No, that's a roundabout way to look at it. Python's variable holds references to objects[1] and never the object themselves; name assignment statement in python never makes a copy of the object, but always makes a new reference to the same object. "Assignment statements" in python includes the '=', 'from import', and regular 'import' [2].
[1] this is call-by-object http://effbot.org/zone/python-objects.htm http://effbot.org/zone/call-by-object.htm [2] there are other more obscure statements that is an 'assignment statement' as well, such as "with ... as ...", "agumented assignment operators", dictionary/list assignment, etc. The list is non-exhaustive.
If you use the 'from import' system, changes made to attrs of the imported module /won't/ be seen by any other module that imported it. If you do just an 'import' on a module (or 'import ... as ...'), then changes made to attrs on the imported module /will /be seen by othe modules that import it as well. I hope that is somewhat clear. ;)
Read both links to effbot's article, they should make it clear why the current behavior is the way it is.
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