---
id: uproot3
version: "3.14.4"
license: BSD 3-clause
license_treatment: permissive
maintenance: abandoned
---

# uproot3 — ROOT I/O in pure Python and Numpy.

License: permissive · Maintenance: abandoned · Downloads: 279.5K/mo

## What it is and what it does

uproot3 is a pure-Python I/O library for reading and writing ROOT files, the standard data format in high-energy physics. It uses NumPy to cast blocks of data from ROOT files as NumPy arrays, avoiding the need to install the C++ ROOT framework. The library is designed to stream data into machine learning pipelines and scientific computing workflows.

The package depends on numpy, awkward0, uproot3-methods, and cachetools. It supports reading compressed ROOT files with optional dependencies like lz4 and xxhash, and can export data to Pandas DataFrames. However, the repository is archived and has not been maintained since 2021-02-19, making it a legacy tool for existing workflows rather than a foundation for new projects.

Use it for:

- Load particle physics data from ROOT files into NumPy arrays for machine learning model training
- Convert ROOT file histograms and trees to Pandas DataFrames for statistical analysis
- Stream large ROOT datasets lazily into memory-constrained environments using cachetools
- Export ROOT file data to other formats without installing the full C++ ROOT framework

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Reads and writes ROOT files (the data format used in high-energy physics) using pure Python and NumPy, without requiring the C++ ROOT library.

No, unless you are maintaining legacy code that already depends on uproot3. The package is abandoned (last commit 2021-02-19) and uses outdated dependencies like awkward0. For new physics data pipelines, consider alternatives with active maintenance.

## Install

pip install uproot3
uv add uproot3
poetry add uproot3

## Installing uproot3

Before you install: Low friction to install. Maintenance is a concern: the repository is archived and the last commit was 2021-02-19, with the package classified as inactive. If you need active development or bug fixes, this is not the right choice.

License in practice: BSD 3-clause is permissive, allowing commercial and private use with minimal restrictions. You must include a copy of the license and disclaimer.

Quickstart:

pip install uproot3

import uproot3
file = uproot3.open('data.root')
tree = file['tree_name']
arrays = tree.arrays()

Requires numpy (1.13.1+), awkward0, uproot3-methods, and cachetools. The package is abandoned and may not work with modern Python or ROOT file formats.

Verify before relying:

- Whether uproot3 works with current ROOT file format versions and modern Python releases
- Whether dependencies like awkward0 remain compatible with current NumPy versions
- Performance characteristics on modern hardware and file sizes

## Package facts

- License: BSD 3-clause (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: abandoned
- Downloads: 279.5K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

ROOT file reader python, read ROOT files numpy, physics data format I/O, ROOT file writer python, HEP data analysis python, ROOT to numpy arrays, particle physics data access, physics-data, legacy-package, hep-tools

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