blackd-client

Tiny HTTP client for the Black (blackd) Python code formatter

Black is a brilliant, opinionated formatter for Python. However it can be quite slow when using an editor integration with format on save, since the process is cold-started every time you call it.

Luckily there's blackd, which is a small HTTP server that keeps the Black process running in the background so that it can be called directly without the lenghty startup time.

blackd-client is a simple helper that provides a single executable to communicate with Black, mainly for me to learn Rust.

If you're using Black (or writing Python code in general) I recommend you to check it out!

Install

Install Black

sh pip install black

or using Homebrew on macOS (preferred)

sh brew install black

Install blackd-client

Download binary from https://github.com/disrupted/blackd-client/releases
Rename to blackd-client and put it somewhere on your PATH

Alternatively if you have Rust toolchain installed:

sh cargo install blackd-client

Start blackd daemon

sh blackd

or as a launchd service using Homebrew on macOS (preferred)

sh sudo brew services start black

Usage

pipe file contents to stdin, e.g.

sh cat main.py | blackd-client

output is formatted using Black :sparkles:

Benchmark comparison

Normal black --fast

sh ❯ hyperfine 'cat subclean/core/parser.py | black --fast -' Time (mean ± σ): 296.8 ms ± 41.3 ms [User: 228.7 ms, System: 51.1 ms] Range (min … max): 260.7 ms … 403.6 ms 10 runs

Using blackd-client

sh ❯ hyperfine 'cat subclean/core/parser.py | blackd-client' Time (mean ± σ): 23.7 ms ± 3.7 ms [User: 2.7 ms, System: 4.8 ms] Range (min … max): 19.2 ms … 35.7 ms 84 runs

Result: blackd is more than 10x faster! :rocket:

Neovim integration

Editor integration for Neovim can be done using a general purpose language server. There are two options to choose from:

null-ls (what I use)
EFM