Choice

class aws_cdk.aws_stepfunctions.Choice(scope, id, *, comment=None, input_path=None, output_path=None)

Bases: State

Define a Choice in the state machine.

A choice state can be used to make decisions based on the execution state.

ExampleMetadata:

infused

Example:

import aws_cdk.aws_lambda as lambda_

# submit_lambda: lambda.Function
# get_status_lambda: lambda.Function


submit_job = tasks.LambdaInvoke(self, "Submit Job",
    lambda_function=submit_lambda,
    # Lambda's result is in the attribute `Payload`
    output_path="$.Payload"
)

wait_x = sfn.Wait(self, "Wait X Seconds",
    time=sfn.WaitTime.seconds_path("$.waitSeconds")
)

get_status = tasks.LambdaInvoke(self, "Get Job Status",
    lambda_function=get_status_lambda,
    # Pass just the field named "guid" into the Lambda, put the
    # Lambda's result in a field called "status" in the response
    input_path="$.guid",
    output_path="$.Payload"
)

job_failed = sfn.Fail(self, "Job Failed",
    cause="AWS Batch Job Failed",
    error="DescribeJob returned FAILED"
)

final_status = tasks.LambdaInvoke(self, "Get Final Job Status",
    lambda_function=get_status_lambda,
    # Use "guid" field as input
    input_path="$.guid",
    output_path="$.Payload"
)

definition = submit_job.next(wait_x).next(get_status).next(sfn.Choice(self, "Job Complete?").when(sfn.Condition.string_equals("$.status", "FAILED"), job_failed).when(sfn.Condition.string_equals("$.status", "SUCCEEDED"), final_status).otherwise(wait_x))

sfn.StateMachine(self, "StateMachine",
    definition=definition,
    timeout=Duration.minutes(5)
)
Parameters:

  • scope (Construct) –

  • id (str) –

  • comment (Optional[str]) – An optional description for this state. Default: No comment

  • input_path (Optional[str]) – JSONPath expression to select part of the state to be the input to this state. May also be the special value DISCARD, which will cause the effective input to be the empty object {}. Default: $

  • output_path (Optional[str]) – JSONPath expression to select part of the state to be the output to this state. May also be the special value DISCARD, which will cause the effective output to be the empty object {}. Default: $

Methods

add_prefix(x)

Add a prefix to the stateId of this state.

Parameters:

x (str) –

Return type:

None

afterwards(*, include_error_handlers=None, include_otherwise=None)

Return a Chain that contains all reachable end states from this Choice.

Use this to combine all possible choice paths back.

Parameters:

  • include_error_handlers (Optional[bool]) – Whether to include error handling states. If this is true, all states which are error handlers (added through ‘onError’) and states reachable via error handlers will be included as well. Default: false

  • include_otherwise (Optional[bool]) – Whether to include the default/otherwise transition for the current Choice state. If this is true and the current Choice does not have a default outgoing transition, one will be added included when .next() is called on the chain. Default: false

Return type:

Chain

bind_to_graph(graph)

Register this state as part of the given graph.

Don’t call this. It will be called automatically when you work with states normally.

Parameters:

graph (StateGraph) –

Return type:

None

otherwise(def_)

If none of the given conditions match, continue execution with the given state.

If no conditions match and no otherwise() has been given, an execution error will be raised.

Parameters:

def –

Return type:

Choice

to_state_json()

Return the Amazon States Language object for this state.

Return type:

Mapping[Any, Any]

to_string()

Returns a string representation of this construct.

Return type:

str

when(condition, next)

If the given condition matches, continue execution with the given state.

Parameters:
Return type:

Choice

Attributes

end_states

Continuable states of this Chainable.

id

Descriptive identifier for this chainable.

node

The construct tree node associated with this construct.

start_state

First state of this Chainable.

state_id

Tokenized string that evaluates to the state’s ID.

Static Methods

classmethod filter_nextables(states)

Return only the states that allow chaining from an array of states.

Parameters:

states (Sequence[State]) –

Return type:

List[INextable]

classmethod find_reachable_end_states(start, *, include_error_handlers=None)

Find the set of end states states reachable through transitions from the given start state.

Parameters:

  • start (State) –

  • include_error_handlers (Optional[bool]) – Whether or not to follow error-handling transitions. Default: false

Return type:

List[State]

classmethod find_reachable_states(start, *, include_error_handlers=None)

Find the set of states reachable through transitions from the given start state.

This does not retrieve states from within sub-graphs, such as states within a Parallel state’s branch.

Parameters:

  • start (State) –

  • include_error_handlers (Optional[bool]) – Whether or not to follow error-handling transitions. Default: false

Return type:

List[State]

classmethod is_construct(x)

Return whether the given object is a Construct.

Parameters:

x (Any) –

Return type:

bool

classmethod prefix_states(root, prefix)

Add a prefix to the stateId of all States found in a construct tree.

Parameters:
Return type:

None