flake8-constants

Flake8 Constants

A Flake8 plugin to detect modifications of constants in Python code, enhancing code quality and preventing unintended behavior.

Why It's Needed

Constants are meant to be immutable values that don't change throughout the execution of a program. However, Python doesn't have built-in support for true constants, relying on naming conventions (all uppercase) to indicate that a variable should be treated as a constant. This plugin helps enforce these conventions by detecting and reporting attempts to modify constants, which can lead to:

1. Improved code reliability: Preventing accidental modifications of values that should remain constant.
2. Better maintainability: Ensuring that constants are used as intended across the codebase.
3. Clearer intent: Helping developers distinguish between mutable variables and immutable constants.
4. Reduced bugs: Catching potential errors early in the development process.

Features

• Detects reassignment of constants (variables with all uppercase names)
• Identifies modifications to class constants
• Catches augmented assignments to constants (e.g., +=, -=)
• Warns about potential modifications through method calls on constants
• Configurable list of non-modifying methods to reduce false positives
• Works across different scopes: global, class, and function levels

Installation

You can install Flake8 Constants using pip:

pip install flake8-constants

Usage

Once installed, flake8 will automatically use this plugin. Run flake8 as usual:

flake8 your_script.py

or integrate it into your existing flake8 configuration.

Configuration

You can configure the plugin by creating a .flake8 file in your project root and adding the following options:

[flake8]
ignore = C001,C005

This example ignores errors related to constant reassignment and augmented assignments.

Error Codes

• C001: Reassignment of constant
• C002: Modification of constant in a function
• C003: Modification of constant in a class method
• C004: Modification of constant in a loop
• C005: Modification of constant in a comprehension

Configuration

No additional configuration is required. The plugin works out of the box with default flake8 settings.

License

This project is licensed under the MIT License - see the LICENSE file for details.