Python Interface

Python bindings and utilities for ROOT.

ROOT is a C++ framework used across HEP for data storage, analysis and visualisation. Its full API is available directly in Python through dynamic bindings powered by cppyy. Every ROOT class you see in the C++ documentation is accessible from Python under the ROOT module.

On top of that, a set of pythonizations adapt selected classes to feel more natively Pythonic: operator overloading, iterators, NumPy interoperability, and more.

Installation

conda pip

conda install -c conda-forge root

pip install root

⚠ Alpha - Linux only.

See root.cern/install for all installation options.

Quickstart

The entry point to ROOT in Python is one import:

import ROOT

Every ROOT class and function is available under the ROOT module.

Now let's create a histogram, fill it from a NumPy array and write it to a file:

import numpy as np
 
# Create a 1D histogram
h = ROOT.TH1D("h", "Gaussian distribution;x;counts", 100, -5, 5)
 
# Fill it from a NumPy array
data = np.random.normal(0, 1, 10000)
h.Fill(data)
 
# Write it to a ROOT file
with ROOT.TFile.Open("output.root", "RECREATE") as f:
    h.Write()

Now we create an RDataFrame from scratch, define a new column with a Python lambda and draw a histogram:

import numpy as np
 
# Create an RDataFrame with 10000 rows
rdf = ROOT.RDataFrame(10000)
 
# Define a column x
rdf = rdf.Define("x", lambda : np.random.normal(0, 1))
 
# Draw a histogram of x
rdf.Histo1D("x").Draw()

Topics
	Interoperability
	Using ROOT alongside other Python packages.
	Pythonizations
	Python-specific functionalities offered by ROOT.
	RDataLoader
	Feed ROOT data directly into models for machine learning training.
	Unified Histogram Interface (UHI)
	Using ROOT histograms in Python.