# Violations¶

Contains detailed information about violation and how to use them.

## Writing new violation¶

First of all, you have to select the correct base class for new violation. The main criteria is what logic will be used to find the flaw in your code.

### Available base classes¶

 ASTViolation Violation for ast based style visitors. MaybeASTViolation Violation for ast and modules visitors. TokenizeViolation Violation for tokenize based visitors. SimpleViolation Violation for cases where there’s no associated nodes.

Violation can not have more than one base class. Since it does not make sense to have two different node types at the same time.

## Violations API¶

ErrorNode = typing.Union[_ast.AST, tokenize.TokenInfo, NoneType]

General type for all possible nodes where error happens.

class BaseViolation(node, text=None)[source]

Bases: object

Abstract base class for all style violations.

It basically just defines how to create any error and how to format this error later on.

Each subclass must define error_template and code fields.

error_template

message that will be shown to user after formatting.

code

violation unique number. Used to identify the violation.

should_use_text

formatting option. Some do not require extra text.

message()[source]

Returns error’s formatted message with code and reason.

Conditionally formats the error_template if it is required.

Return type: str
node_items()[source]

Returns tuple to match flake8 API format.

Return type: Tuple[int, int, str]
class ASTViolation(node, text=None)[source]

Bases: wemake_python_styleguide.violations.base._BaseASTViolation

Violation for ast based style visitors.

class MaybeASTViolation(node=None, text=None)[source]

Bases: wemake_python_styleguide.violations.base._BaseASTViolation

Violation for ast and modules visitors.

Is used for violations that share the same rule for nodes and module names. Is wildly used for naming rules.

class TokenizeViolation(node, text=None)[source]

Violation for tokenize based visitors.

class SimpleViolation(node=None, text=None)[source]

Violation for cases where there’s no associated nodes.