ObservableModule #8

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1. nocarryr commented on Oct 29, 2019

   

   nocarryr

   on Oct 29, 2019

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   Can you elaborate a little on this? Something like a subclass of Observable that tracks changes to a module's __dict__ attribute?
2. jayvdb commented on Oct 29, 2019

   

   jayvdb

   on Oct 29, 2019

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   Ya, that is roughly what I had in mind. And if recursive, then also the containers within the module. And tracking __slots__ would be the other major source of change for a module.
3. jayvdb commented on Oct 29, 2019

   

   jayvdb

   on Oct 29, 2019

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   Ideally something like

   import sys, pydispatch
   sys_change_emitter = pydispatch.wrap(sys)
4. nocarryr commented on Oct 29, 2019

   

   nocarryr

   on Oct 29, 2019

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   In order to do that, the module's __dict__ would have to be replaced with an ObservableDict copy.

   I'm not sure how that would impact the module's references to its own objects at that point though. For pure-python modules, it may be fine, but for modules relying on binary extensions (like most of Python's standard lib) there could be some crazy side effects.

   If doing that recursively, other imported modules (since they're in the __dict__ as well) would either be wrapped or skipped, with some sort of tracking mechanism to avoid circular references (wrapping the same module over and over).

   It sounds like fun, lol! But I think it'd be hard to keep things from breaking
5. nocarryr commented on Oct 29, 2019

   

   nocarryr

   on Oct 29, 2019

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   According to https://docs.python.org/3/reference/datamodel.html#the-standard-type-hierarchy a module's __dict__ is read-only:

   Modules
   Modules are a basic organizational unit of Python code...
   ...
   Special read-only attribute: __dict__ is the module’s namespace as a dictionary object.
6. jayvdb commented on Oct 30, 2019

   

   jayvdb

   on Oct 30, 2019

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   module's dict is read-only

   ya, the __dict__ contents are modifiable, but the __dict__ itself cant be replaced.

   >>> import os
   >>> len(os.__dict__.keys())
   344
   >>> os.__dict__['foo'] = 'bar'
   >>> len(os.__dict__.keys())
   345
   >>> os.__dict__ = dict(os.__dict__)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   AttributeError: readonly attribute

   But the wrapper will need to create a new module object. Last time I did this, I used a normal class as the module wrapper (e.g. https://github.com/rinslow/fakeos/blob/master/fakeos.py#L13), and added module-like attributes so it acted like a module, like https://github.com/Akrog/modulefaker/blob/master/modulefaker/__init__.py#L35.

   More modern attempts use the new import machinery voodoo to create real module objects which inherit from the correct classes.
   https://github.com/rominf/module-wrapper looks interesting
   iirc https://github.com/GrahamDumpleton/wrapt didnt have a module wrapper.
7. jayvdb commented on Oct 30, 2019

   

   jayvdb

   on Oct 30, 2019

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   "module proxy" should be a good term, except it is full of http proxy stuff. Lazy module loaders may be useful to see how to do this, and search results tend to be more useful. https://github.com/cacilhas/ObjectProxy