PyTorch C++-generated module "not found as" itself?

[ringohoffman]

My example is in the latest version of torch==2.3.0:

$ pip install torch dill

There is a module in torch._C._dynamo called eval_frame that is not importable as such:

import torch._C._dynamo

print(torch._C._dynamo.eval_frame)  # <module 'torch._C._dynamo.eval_frame'>

import torch._C._dynamo.eval_frame  # ModuleNotFoundError: No module named 'torch._C._dynamo.eval_frame'; 'torch._C._dynamo' is not a package

I suppose it is like an imported module. It is a C++ binding: https://github.com/pytorch/pytorch/blob/556e4ec6c93d4ccfbf84cffe462308340417a95b/torch/csrc/dynamo/init.cpp#L58

When I try to pickle attributes of eval_frame using dill, I get a PicklingError:

import dill
import torch._C._dynamo

print(torch._C._dynamo.eval_frame._CacheEntry)  # <class 'torch._C._dynamo.eval_frame._CacheEntry'>

with open("a.pkl", "wb") as f:
    dill.dump(torch._C._dynamo.eval_frame._CacheEntry, f)  # PicklingError: Can't pickle <class 'torch._C._dynamo.eval_frame._CacheEntry'>: it's not found as torch._C._dynamo.eval_frame._CacheEntry

Is this being mishandled by dill or could there be something malformed about the eval_frame module?

[ringohoffman]

Seems like it could be a more fundamental issue with pickle:

• submodule of c-extension module is quirky python/cpython#87533 (comment)

Looking for feedback.