[Python-Dev] is sys.modules not meant to be replaced?

[Eric Snow]

On Sat, Jul 23, 2011 at 10:55 PM, Benjamin Peterson <benjamin at python.org> wrote:
> 2011/7/23 Eric Snow <ericsnowcurrently at gmail.com>:
>> The documentation[1] doesn't say, but the implementation of the imp
>> module makes me wonder if sys.modules was not meant to be replaceable.
>>  No doubt this has to do with its tie to the interpreter's modules
>> dict.  I ran into this doing "sys.modules = sys.modules.copy()" to
>> protect the actual sys.modules dict during some import related test
>> cases.  If the modules I imported were extension modules it broke.
>>
>> So, is sys.modules not meant to be open to re-binding?
>
> Not any more or less than other global mutable objects. You can expect
> other code to be holding on to old references.

But, isn't sys.modules a little different because other modules (at
least the imp module) don't use it.  From what I understand the
interpreter object's modules dict (to which sys.modules is initially
bound) is used directly instead.  So rebinding sys.modules causes a
disconnect.  That's why I am wondering if sys.modules is not meant to
be rebound.

Are there other objects in the interpreter state that are exposed in
sys that would have the same problem?

-eric

>
>
> --
> Regards,
> Benjamin
>