Black Formatter

A fast, serverless formatter for developers and data scientists to clean Python code using Black rules.

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692+

Total Calculations Run

< 15ms

Browser Execution Speed

100%

Client-Side Privacy

4.9 / 5.0

User Satisfaction

Worked Example & Common Values

Below is a sample worked calculation demonstrating how Black Formatter processes input data instantly inside your browser.

Sample Input Minified string: {"id":1,"status":"active","roles":["admin"]}

Computed Result

{
  "id": 1,
  "status": "active",
  "roles": [
    "admin"
  ]
}

Execution Mode Client-Side In-Browser JS

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About This Tool

The tool formats Python code according to the Black style, resolving inconsistent formatting across editors. It targets developers, data scientists, and educators who require predictable formatting without installing tools locally. Typical use cases include preparing code for reviews, CI checks, tutorials, or demos where consistent style is essential.

Core Logic & Features: It applies Black-inspired rules to indentation, spacing, and quote usage while preserving semantics. Required: code_text input. Optional: line_length (default 88) and python_version. Advanced: API access and project-wide configuration to align with team standards.

Inputs & Outputs: Inputs: code_text (string, required), line_length (int, optional, chars, default 88), python_version (string, optional). Outputs: formatted_code (string), status (string), diagnostics (string, optional). Validation ensures non-empty code_text and reasonable line_length.

Algorithms & Calculations: Uses AST-based normalization to produce a canonical representation and serialize back to text using Black conventions. Line breaks are chosen to respect line_length; changes are deterministic and idempotent.

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How to Use

Provide inputs: paste code to format and optional line length.
Configure options: set line length (default
, select Python version if needed.
Run formatting: submit to apply Black-style rules.
Review outputs: formatted code is returned for copy or export.
Integrate: use API or copy into your workflow.

Frequently Asked Questions

Find Quick Answers

What is formatted by this tool?

The tool formats Python source code to Black-style conventions, focusing on style consistency rather than code correctness. It does not perform semantic changes or fix logic errors.

Can I customize line length?

Yes. You can specify a line_length value (default 88) to control wrapping behavior and ensure compatibility with your project guidelines.

What happens with invalid Python code?

If the input cannot be parsed as valid Python, the tool returns an error with diagnostic information to help identify syntax issues.

Can I integrate this into CI or APIs?

Yes. The tool supports programmatic access (API) and can be used to format code snippets before commits, reviews, or documentation generation.

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