Error Node | Vellum | Documentation

from vellum.workflows import BaseWorkflow
from vellum.workflows.nodes import ErrorNode
from vellum.workflows.inputs.base import BaseInputs
from vellum.workflows.state import BaseState
class Inputs(BaseInputs):
    threshold: int
class StartNode(BaseNode):
    class Ports(BaseNode.Ports):
        success = Port.on_if(Inputs.threshold.greater_than(10))
        fail = Port.on_else()
class SuccessNode(BaseNode):
    class Outputs(BaseNode.Outputs):
        result = Inputs.threshold
class FailNode(ErrorNode):
    error = "Input threshold was too low"
class BasicErrorNodeWorkflow(BaseWorkflow[Inputs, BaseState]):
    graph = {
        StartNode.Ports.success >> SuccessNode,
        StartNode.Ports.fail >> FailNode,
    }
    class Outputs(BaseWorkflow.Outputs):
        final_value = SuccessNode.Outputs.result

vellum.workflows.nodes.ErrorNode

Used to raise an error to reject the surrounding Workflow and return custom error messages.

Attributes

error

Union[str, VellumError]Required

The error to raise. Can be either:

A string message
A VellumError object with a message and error code

Outputs

This node doesn’t produce outputs. However, Workflows that invoke this node will error and the error message will appear in the Vellum UI.

1	from vellum.workflows import BaseWorkflow
2	from vellum.workflows.nodes import ErrorNode
3	from vellum.workflows.inputs.base import BaseInputs
4	from vellum.workflows.state import BaseState
5
6	class Inputs(BaseInputs):
7	threshold: int
8
9	class StartNode(BaseNode):
10	class Ports(BaseNode.Ports):
11	success = Port.on_if(Inputs.threshold.greater_than(10))
12	fail = Port.on_else()
13
14	class SuccessNode(BaseNode):
15	class Outputs(BaseNode.Outputs):
16	result = Inputs.threshold
17
18	class FailNode(ErrorNode):
19	error = "Input threshold was too low"
20
21	class BasicErrorNodeWorkflow(BaseWorkflow[Inputs, BaseState]):
22	graph = {
23	StartNode.Ports.success >> SuccessNode,
24	StartNode.Ports.fail >> FailNode,
25	}
26	class Outputs(BaseWorkflow.Outputs):
27	final_value = SuccessNode.Outputs.result