textual.validation

This module provides a number of classes for validating input.

See Validating Input for details.

Failure dataclass

Failure(validator, value=None, description=None)

Information about a validation failure.

description class-attribute instance-attribute

description = None

An optional override for describing this failure. Takes precedence over any messages set in the Validator.

validator instance-attribute

validator

The Validator which produced the failure.

value class-attribute instance-attribute

value = None

The value which resulted in validation failing.

Function

Function(function, failure_description=None)

Bases: Validator

A flexible validator which allows you to provide custom validation logic.

function instance-attribute

function = function

Function which takes the value to validate and returns True if valid, and False otherwise.

ReturnedFalse dataclass

ReturnedFalse(validator, value=None, description=None)

Bases: Failure

Indicates validation failed because the supplied function returned False.

describe_failure

describe_failure(failure)

Describes why the validator failed.

Parameters:

Name	Type	Description	Default
failure	Failure	Information about why the validation failed.	required

Returns:

Type	Description
str | None	A string description of the failure.

validate

validate(value)

Validate that the supplied function returns True.

Parameters:

Name	Type	Description	Default
value	str	The value to pass into the supplied function.	required

Returns:

Type	Description