AttributeError for eventsProcessed in latest key4hep stack (-r 2026-02-01)

sbakare · March 17, 2026, 2:43am

Hello,
I ran into an error : AttributeError: 'TNetXNGFile' object has no attribute 'eventsProcessed' when using the latest key4hep stack (source /cvmfs/sw.hsf.org/key4hep/setup.sh -r 2026-02-01)

Interestingly, this same pipeline works perfectly for older stack (source /cvmfs/sw.hsf.org/key4hep/setup.sh -r 2025-05-29).

I believe this is happening because the 2025-05-29 release uses ROOT 6.32, while the 2026-02-01 release was updated to ROOT 6.38. It looks like PyROOT’s lookup in run_analysis.py (infile.eventsProcessed.GetVal()) is causing this error with the newer ROOT version.

To get around it, I changed that line to: infile.Get("eventsProcessed").GetVal()

After recompiling FCCAnalyses, this seems to solve the issue. Maybe we need to address this upstream, or please correct me if I am missing something.

Cheers,
Shreyas

jsmiesko · March 17, 2026, 9:16am

Hi @sbakare,

nice catch, can you create a PR with this fix?

Best,
Juraj

sbakare · March 18, 2026, 12:45pm

Hello @jsmiesko ,

I have updated the eventsProcessed extraction logic to handle the new stack and added a fallback warning for missing metadata. I have submitted a Pull Request with the fix here:

github.com/HEP-FCC/FCCAnalyses

Fix: Update eventsProcessed lookup for ROOT 6.38 and add fallback warning

master ← ShreyasBakare:fix/metadata-extraction

opened 12:29PM - 18 Mar 26 UTC

ShreyasBakare

+9 -4

This PR addresses an AttributeError encountered when reading metadata using the …latest Key4hep stack, as reported in [this FCCSW-Forum post](https://fccsw-forum.web.cern.ch/t/attributeerror-for-eventsprocessed-in-latest-key4hep-stack-r-2026-02-01/267). The `run_histmaker` function in `python/run_analysis.py` previously used PyROOT's dynamic attribute lookup to check for the 'eventsProcessed' `TParameter`. On the newer Key4hep stack (`-r 2026-02-01`), which updates to ROOT 6.38, this dynamic lookup fails, leading to the following error when reading files from EOS: ``` AttributeError: 'TNetXNGFile' object has no attribute 'eventsProcessed' ``` To resolve this incompatibility, this PR replaces the dynamic lookup `infile.eventsProcessed.GetVal()` with `infile.Get("eventsProcessed").GetVal()`. **Additional improvements in this PR:** - Removed the `GetListOfKeys()` loop, fetching the parameter directly. - Added a `LOGGER.warning`. If a user runs Stage 2 (or later) scripts on an input file missing this metadata tag (e.g., after intermediate processing with `uproot`), the framework will explicitly warn them that cross-section scaling will fall back to the current tree's entry count, which may artificially inflate results. As described in [this FCCSW-Forum post](https://fccsw-forum.web.cern.ch/t/inflated-scaling-in-stage-2-when-using-intermediate-tools-like-uproot/266). This change can be tested by running any Stage 2 histmaker script over EOS files (root://eosuser.cern.ch/...) on the new Key4hep stack (`-r 2026-02-01`).

Best,
Shreyas