uv with Charlie Marsh

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May 15, 2025

In this conversation with Charlie Marsh, the Founder and CEO of Astral, we dive into the evolution of Python tooling and how Rust is reshaping the landscape. Charlie shares insights on Astral's mission to unify and enhance the Python ecosystem through innovative tools like UV and Ruff. He discusses the complexities of package management, the challenges of async programming, and the journey of developing a custom Python parser in Rust. Expect engaging stories and practical tips that illustrate the synergy between these programming languages.

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INSIGHT

Complexity of requirements.txt

The Python requirements.txt format is complex, treating each line as a CLI argument including nested files and options.
Mimicking pip’s behavior requires deep source code reading since the format is implementation-defined and nuanced.

ANECDOTE

Cross-Platform CI Testing

Astral tests uv on Linux, macOS, and Windows for every change due to platform-specific differences.
They build 10-20 variants targeting diverse architectures, including niche platforms like PowerPC and s390x.

INSIGHT

Benefit of Pure Rust Dependencies

Using pure Rust libraries like zlib-rs simplifies cross-platform building and improves performance.
Moving away from C dependencies reduces build complexity and platform-specific configuration challenges.

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Up until a few years ago, Python tooling was a nightmare: basic tasks like installing packages or managing Python versions was a pain. The tools were brittle and did not work well together.

Then, suddenly, we saw a renaissance of new ideas in the Python ecosystem. It started with Poetry and pipx and continued with tooling written in Rust like rye, which later got incorporated into Astral.

Astral in particular contributed a very important piece to the puzzle: uv -- an extremely fast Python package and project manager that supersedes all previous attempts; For example, it is 10x-100x faster than pip.

In this episode I talk to Charlie Marsh, the Founder and CEO of Astral. We talk about Astral's mission and how Rust plays an important role in it.

About Astral

Astral is a company that builds tools for Python developers. What sounds simple is actually a very complex problem: Python's ecosystem is huge, but fragmented and often incompatible. Astral’s mission is to make the Python ecosystem more productive by building high-performance developer tools, starting with Ruff. In their words: "Fast, unified, futuristic."

About Charlie Marsh

Charlie is a long-time open source developer and entrepreneur. He has an impressive CV, graduating with highest honors from Princeton University. After that, he worked at Khan Academy and others before eventually founding Astral in '22. Charlie is an engaging speaker and a great communicator.

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Links From The Episode

ruff - Python static linter and formatter written in Rust
uv - Python package and project manager written in Rust
rustfmt - Rust code formatter
clippy - Linter for Rust code
The Rust Programming Language: Cargo Workspaces - The Rust Book's chapter on workspaces
pip - Package Installer for Python
pip documentation: Requirements File Format - A description of the format of requirements.txt, including a list of embedded CLI options
uv's CI - Build scripts for many different platforms
jemalloc - Alternative memory allocator
zlib-ng - Next Generation zlib implementation in C
reqwest - An easy and powerful Rust HTTP Client
zlib-rs - Pure Rust implementation of zlib
XCode Instruments - Native macOS performance profiler
CodSpeed - Continuous benchmarking in CI
hyperfine - "macro benchmarking" tool, coincidentally written in Rust
samply - Sampling based profiler written in Rust
cargo flamegraph - Cargo profiling plugin
tokio - Asynchronous runtime for Rust
curl-rust - Network API used in cargo
tar-rs - Sync tar crate
async-tar - Async tar crate based on the async_std runtime
tokio-tar - Async tar crate based on tokio
astral-tokio-tar - Async tar crate based on tokio, maintained by Astral
RustPython - Python interpreter written in Rust
lalrpop - The parser generator used by RustPython
Charlie's EuroRust 2024 Talk - Mentions the version number parser at 18:45
ripgrep - Andrew Gallant's idiomatic Rust project, which also happens to be a very fast CLI file search tool

Official Links