Hi, I would like to know if it is possible to dynamically access objects from the files currently being processed by the RDataFrame event loop. In particular, I would like to read the bin content of a histogram from the same file which holds the TTree, define the value as a column using DefinePerSa…

Dear @cgrefe , Thank you for reaching out to the ROOT forum! The use case you are presenting is intriguing. If I understand correctly, you would like to have an interface that lets you access at the same time any arbitrary content in a ROOT file, during the event loop while processing a ROOT dataset…

Hi Vincenzo, the overhead is not significant if it is a small number of files available locally. I am more worried about the case of hundreds or even thousands of files to process, which might be stored on some remote storage (i.e. EOS). So just opening each file to pre-fetch the metadata before ev…

A reply from the future: Use DefinePerSample Access the file as needed Details here: [image] Current root file in RDataframe ROOT There is a topic from last year which seems to ask the same question (see below), but it never got a definite answer. Is there a…

Reading object from file currently processed in RDataFrame

ROOT

StephanH September 17, 2026, 7:20am 5

A reply from the future:

Use DefinePerSample
Access the file as needed

Details here: