Validators¶

Validators are ordinary callables that take a single argument (the input value) and return a transformed result value. They can also raise validation errors.

IValidator(value)¶

Validates the input value and possibly transforms it.

Returns the new value. If the value is invalid, raises a decent.error.Error or decent.error.Invalid exception.

Validator callables can be used inside schemas, but also standalone.

Built-in validators¶

Decent ships with many built-in validators that can be used and combined for usual tasks. Instances of them are built through the following constructors:

Helpers & Building blocks¶

decent.validators.All(*validators): Combines all the given validator callables into one, running all the validators in sequence on the given value.

decent.validators.Any(*validators): Combines all the given validator callables into one, running the given value through them in sequence until a valid result is given.

decent.validators.Default(default): Creates a validator callable that replaces None with the specified default value.

decent.validators.Maybe(validator): Wraps the given validator callable, only using it for the given value if it is not None.

decent.validators.Msg(validator, message): Wraps the given validator callable, replacing any error messages raised.

Basics¶

decent.validators.Eq(value, message='Not equal to {!s}')

Creates a validator that compares the equality of the given value to value.

A custom message can be specified with message. It will be formatted with value.

decent.validators.Coerce(type, message='Not a valid {} value')

Creates a validator that attempts to coerce the given value to the specified type. Will raise an error if the coercion fails.

A custom message can be specified with message.

decent.validators.Instance(expected, message='Not an instance of {}')

Creates a validator that checks if the given value is an instance of expected.

A custom message can be specified with message.

decent.validators.Type(expected, message='Not of type {}')

Creates a validator that compares the type of the given value to expected. This is a direct type() equality check. Also see Instance, which is an isinstance() check.

A custom message can be specified with message.

Collections¶

decent.validators.List(validator)

Creates a validator that runs the given validator on every item in a list or other collection. The validator can mutate the values.

Any raised errors will be collected into a single Invalid error. Their paths will be replaced with the index of the item. Will raise an error if the input value is not iterable.

decent.validators.Length(min=None, max=None, min_message='Must have a length of at least {min}', max_message='Must have a length of at most {max}')

Creates a validator that checks if the given value’s length is in the specified range, inclusive. (Returns the original value.)

See Range().

Booleans¶

decent.validators.Boolean()

Creates a validator that attempts to convert the given value to a boolean or raises an error. The following rules are used:

None is converted to False.

int values are True except for 0.

str values converted in lower- and uppercase:

y, yes, t, true
n, no, f, false

Numbers¶

decent.validators.Range(min=None, max=None, min_message='Must be at least {min}', max_message='Must be at most {max}')

Creates a validator that checks if the given numeric value is in the specified range, inclusive.

Accepts values specified by numbers.Number only, excluding booleans.

The error messages raised can be customized with min_message and max_message. The min and max arguments are formatted.

decent.validators.Length(min=None, max=None, min_message='Must have a length of at least {min}', max_message='Must have a length of at most {max}')

Creates a validator that checks if the given value’s length is in the specified range, inclusive. (Returns the original value.)

See Range().

Strings¶

decent.validators.Lower(): Creates a validator that converts the input string to lowercase. Will raise an error for non-string types.

decent.validators.Upper(): Creates a validator that converts the input string to UPPERCASE. Will raise an error for non-string types.

decent.validators.Strip(): Creates a validator that strips the input string of whitespace. Will raise an error for non-string types.

decent.validators.Length(min=None, max=None, min_message='Must have a length of at least {min}', max_message='Must have a length of at most {max}')

Creates a validator that checks if the given value’s length is in the specified range, inclusive. (Returns the original value.)

See Range().

String conversions¶

decent.validators.Uuid(to_uuid=True)

Creates a UUID validator. Will raise an error for non-string types and non-UUID values.

The given value will be converted to an instance of uuid.UUID unless to_uuid is False.