Скачать или смотреть Fixing UnpicklingError: pickle data was truncated When Using dill.load_session() in Jupyter Noteboo

Learn how to properly save and load Jupyter notebook sessions with dill to avoid data truncation errors and corrupted pickle files.
---
This video is based on the question https://stackoverflow.com/q/79496572/ asked by the user 'Rushil Patel' ( https://stackoverflow.com/u/29951508/ ) and on the answer https://stackoverflow.com/a/79496594/ provided by the user 'Lewis' ( https://stackoverflow.com/u/28442916/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: dill.load_session() causes `UnpicklingError: pickle data was truncated` even though dill.dump_session() pickled perfectly fine

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to drop me a comment under this video.
---
Problem Overview

When saving the entire state of a Jupyter notebook session using dill.dump_session(), you might encounter an error when reloading:

[[See Video to Reveal this Text or Code Snippet]]

This typically happens even though the .pkl file initially appears correctly saved with a large size. After attempting to load the session using dill.load_session(), the file can become empty, corrupting your saved state.

Why This Happens

The most common cause is that the pickle file was not fully flushed to disk before the notebook or interactive node session was terminated. This leads to an incomplete or truncated pickle file despite dump_session() seemingly completing.

Best Practices to Safely Save and Load Sessions

To prevent incomplete writes and file truncation, explicitly flush and sync the file buffer after dumping:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

f.flush() ensures Python pushes all buffered data out to the operating system.

os.fsync() ensures the operating system writes this data to the physical disk.

Together, these guarantee that your session data isn’t lost if the notebook or session closes suddenly.

Additional Tips

Always close your file handle properly, ideally using a with statement.

Avoid terminating interactive nodes or Jupyter kernels before saving and flushing data.

For very large sessions, consider saving important objects separately rather than the entire session.

Summary

The UnpicklingError due to truncated data typically arises from incomplete writes of your pickle file caused by missing flush/sync calls. Explicitly flushing and syncing your file after dill.dump_session() is a simple and effective fix.

This approach protects your saved state files, making your notebook workflows more robust and reliable.