Rdataframe define column of same constant value

ROOT
8

I’m still a little bit confused about what the actual problem is, feel free to post a reproducer! I think you want to do something like this?

import ROOT
w = 42.0
df = ROOT.RDataFrame(4).Define("x", "float(rdfentry_)").Define("w", str(w))
h = df.Histo1D("x", "w")
h.Draw()

This returns the (correct) plot below.

x

Best
Stefan