Get pnl running in your project in three steps.

Step 1: Create a Config File¶

Create .python-naming-linter.yaml in your project root and define your naming rules:

rules:
  - name: bool-method-prefix
    type: function
    filter: { return_type: bool }
    naming: { prefix: [is_, has_, should_] }

  - name: exception-naming
    type: class
    filter: { base_class: Exception }
    naming: { regex: "^[A-Z][a-zA-Z]+(NotFound|Invalid|Denied|Conflict|Failed)Error$" }

apply:
  - name: all
    rules: [bool-method-prefix, exception-naming]
    modules: "**"

This config defines two rules:

• bool-method-prefix — functions that return bool must start with is_, has_, or should_.
• exception-naming — classes that extend Exception must follow the given regex pattern.

Both rules are applied to all modules (**).

Step 2: Run the Linter¶

From your project root, run:

pnl check

pnl automatically discovers the config file by searching upward from the current working directory.

Step 3: Review the Output¶

Violations are reported with the file path, line number, rule name, and what was expected:

src/domain/service.py:12
    [bool-method-prefix] validate (expected prefix: is_ | has_ | should_)

src/domain/exceptions.py:8
    [exception-naming] FilterError (expected pattern: ^[A-Z][a-zA-Z]+(NotFound|Invalid|...)Error$)

Found 2 violation(s).

Fix the reported names and re-run pnl check until no violations remain.

Next Steps¶

• Learn all available config options in Configuration.
• See rule type details and naming constraint options in the full reference.