---
title: "UV the new python package installer written in Rust"
date: 2024-02-25
slug: "uv-the-new-python-package-installer-written-in-rust"
tags: ["CI/CD", "docker", "python", "tools"]
type: "programming"
---

## Overview
[UV](https://astral.sh/blog/uv) is Team Astral's new tool. It's written in Rust and aims to replace `pip` and `pip-tools`, all with extreme speed.

After the publication of [Ruff](https://astral.sh/ruff), the team continues with the aim of creating a "Cargo for Python" with this new publication.

UV can be installed in several ways (with pip or standalone) and is compatible with Linux, Windows and macOS. I installed it with the following command:
```bash
pip install uv
```

To use it, simply use the `uv` prefix and then one of the following commands:
```bash
# Basic command like install, uninstall, freeze, sync, compile
uv pip
# Create a VENV
uv venv
# Clean cache or show cache directory
uv cache
```

## UV benchmark
Let's compare UV and VENV/PIP to see how this new solution performs. According to the creators, UV should be around 80x faster than `python -m venv` and 7x faster than `virtualenv`.

After creating virtual environments with these different tools, I was able to obtain the following results:

{{< chart >}}
type: 'bar',
data: {
  labels: ['uv', 'virtualenv', 'venv'],
  datasets: [{
    data: [0.010, 0.153, 1.539],
  }]
},
options: {
  indexAxis: 'y',
  elements: {
    bar: {
      borderWidth: 2,
    }
  },
  responsive: true,
  plugins: {
    legend: {
      display: false,
    },
    title: {
      display: true,
      text: 'Virtual environment creation'
    }
  }
}
{{< /chart >}}

In my case, UV is ~15x faster than `virtualenv` and ~150x faster than `python -m venv`. I then tried installing python packets with UV and PIP to compare speeds:

{{< chart >}}
type: 'bar',
data: {
  labels: ['uv', 'uv+cache', 'pip'],
  datasets: [{
    data: [2.961, 0.413, 13.917],
  }]
},
options: {
  indexAxis: 'y',
  elements: {
    bar: {
      borderWidth: 2,
    }
  },
  responsive: true,
  plugins: {
    legend: {
      display: false,
    },
    title: {
      display: true,
      text: 'Packages install (~100)'
    }
  }
}
{{< /chart >}}

For packet insertion I find that UV is ~5x faster than pip and ~33x faster then `pip` with the UV cache.

## Docker image for CI/CD
Now let's try to integrate it into our CIs. To do this, I'll create a modified python image that I'll then use in my various workflows.
```dockerfile
FROM python:3.11-slim

RUN python3 -m pip install --upgrade pip && \
    pip3 install uv && \
    uv venv && \
    . /.venv/bin/activate && \
    uv pip install ruff

ENV VIRTUAL_ENV /.venv
ENV PATH /.venv/bin:$PATH
```

The Dockerfile is quite simple, I base it on a python 3.11 image, upgrade pip, then install UV. I then create a venv with UV, and activate it. Finally, I install the packets I need for my workflows.

Finally, I set the environment variables `VIRTUAL_ENV` and `PATH`. This allows me to be directly in the venv when using the image. I then build the image and check that it works correctly:
```bash
debian@debian:~/dev/images$ docker build -t uv_python .
[...]
debian@debian:~/dev/images$ docker run -it --rm uv_python bash
root@ec910e7ea8eb:/# uv pip install django
Resolved 3 packages in 483ms
Downloaded 3 packages in 584ms
Installed 3 packages in 150ms
 + asgiref==3.7.2
 + django==5.0.2
 + sqlparse==0.4.4
root@ec910e7ea8eb:/# python3
Python 3.11.8 (main, Feb  7 2024, 22:49:54) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import django
>>>
```

After building and testing the image with a docker run, I can confirm that the image works correctly and is usable in my various CIs.

In addition to this image, we can set the cache for UV in Workflow. For Gitlab, I use the following configuration:
```yml
[...]
variables:
  UV_CACHE_DIR: "$CI_PROJECT_DIR/.cache/uv"

cache:
  - key: uv-pip-cache
    paths:
      - $CI_PROJECT_DIR/.cache/uv
[...]
```

After a few, I've noticed that the cache can be useful in some situations (especially if you have a very good machine) but can also slow down the CI in others. In some situations, UV is faster than Gitlab's cache compression/decompression. In particular, I've seen it slow down runners using HDDs.

I suggest you test with and without to see which is faster.

## Conclusion

UV is a very promising tool, in line with what Team Astral has to offer. In my opinion, it can already be deployed in production, and therefore saves a great amont of time, especially for repeat installations (e.g. CI). The speed of this tool even calls into question some current time-saving options, such as the CI cache.

It's worth noting that, despite the objective of being a "drop-in replacement for pip", it currently lacks features that could be blocking in certain situations:
- No --trusted-host option ([#1339](https://github.com/astral-sh/uv/issues/1339))
- No installation without venv ([#1374](https://github.com/astral-sh/uv/issues/1374))
- etc.