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dandavison committed Aug 6, 2024
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Expand Up @@ -182,165 +182,11 @@ Notice that:

Non-dynamic methods can only have positional arguments.

**How to customize names**

You can have a name parameter to customize the Signal's name, otherwise it defaults to the name of the Signal method.

<div class="copycode-notice-container">
<a href="https://github.com/temporalio/documentation/blob/main/sample-apps/python/signal_your_workflow/wf_signal_dacx.py">
View the source code
</a>
in the context of the rest of the application code.
</div>

```python
from temporalio import workflow
# ...
@workflow.signal
async def submit_greeting(self, name: str) -> None:
await self._pending_greetings.put(name)

@workflow.signal
def exit(self) -> None:
# ...
@workflow.signal(name="Custom Signal Name")
async def custom_signal(self, name: str) -> None:
await self._pending_greetings.put(name)
```

### Handle Signal {#handle-signal}

**How to handle a Signal using the Python SDK.**

Workflows listen for Signals by the Signal's name.

Signal handlers are functions defined in the Workflow that listen for incoming Signals of a given type.
These handlers define how a Workflow should react when it receives a specific type of Signal.

To send a Signal to the Workflow, use the [signal](https://python.temporal.io/temporalio.client.WorkflowHandle.html#signal) method from the [WorkflowHandle](https://python.temporal.io/temporalio.client.WorkflowHandle.html) class.

<div class="copycode-notice-container">
<a href="https://github.com/temporalio/documentation/blob/main/sample-apps/python/signal_your_workflow/signal_dacx.py">
View the source code in the context of the rest of the application code.
</a>

</div>

```python
from temporalio.client import Client
# ...
# ...
await handle.signal(GreetingWorkflow.submit_greeting, "User 1")
```

### Send a Signal from a Temporal Client {#send-signal-from-client}

**How to send a Signal from a Temporal Client using the Python SDK.**

When a Signal is sent successfully from the Temporal Client, the [WorkflowExecutionSignaled](/references/events#workflowexecutionsignaled) Event appears in the Event History of the Workflow that receives the Signal.

To send a Signal from the Client, use the [signal()](https://python.temporal.io/temporalio.client.WorkflowHandle.html#signal) function on the Workflow handle.

To get the Workflow handle, you can use any of the following options.

- Use the [get_workflow_handle()](https://python.temporal.io/temporalio.client.Client.html#get_workflow_handle) method.
- Use the [get_workflow_handle_for()](https://python.temporal.io/temporalio.client.Client.html#get_workflow_handle_for) method to get a type-safe Workflow handle by its Workflow Id.
- Use the [start_workflow()](https://python.temporal.io/temporalio.client.Client.html#start_workflow) to start a Workflow and return its handle.

<div class="copycode-notice-container">
<a href="https://github.com/temporalio/documentation/blob/main/sample-apps/python/signal_your_workflow/signal_dacx.py">
View the source code
</a>{' '}
in the context of the rest of the application code.
</div>

```python
from temporalio.client import Client
# ...
# ...
client = await Client.connect("localhost:7233")
handle = await client.start_workflow(
GreetingWorkflow.run,
id="your-greeting-workflow",
task_queue="signal-tq",
)
await handle.signal(GreetingWorkflow.submit_greeting, "User 1")
```

### Send a Signal from a Workflow {#send-signal-from-workflow}

**How to send a Signal from a Workflow using the Python SDK.**

A Workflow can send a Signal to another Workflow, in which case it's called an _External Signal_.

When an External Signal is sent:

- A [SignalExternalWorkflowExecutionInitiated](/references/events#signalexternalworkflowexecutioninitiated) Event appears in the sender's Event History.
- A [WorkflowExecutionSignaled](/references/events#workflowexecutionsignaled) Event appears in the recipient's Event History.

Use [`get_external_workflow_handle_for`](https://python.temporal.io/temporalio.workflow.html#get_external_workflow_handle_for) to get a typed Workflow handle to an existing Workflow by its identifier.
Use [`get_external_workflow_handle`](https://python.temporal.io/temporalio.workflow.html#get_external_workflow_handle) when you don't know the type of the other Workflow.

:::note

The Workflow Type passed is only for type annotations and not for validation.

:::

<div class="copycode-notice-container">
<a href="https://github.com/temporalio/documentation/blob/main/sample-apps/python/signal_your_workflow/signal_external_wf_dacx.py">
View the source code in the context of the rest of the application code.
</a>{' '}

</div>

```python
# ...
@workflow.defn
class WorkflowB:
@workflow.run
async def run(self) -> None:
handle = workflow.get_external_workflow_handle_for(WorkflowA.run, "workflow-a")
await handle.signal(WorkflowA.your_signal, "signal argument")
```

### Signal-With-Start {#signal-with-start}

**How to send a Signal-With-Start using the Python SDK.**

Signal-With-Start is used from the Client.
It takes a Workflow Id, Workflow arguments, a Signal name, and Signal arguments.

If there's a Workflow running with the given Workflow Id, it will be signaled. If there isn't, a new Workflow will be started and immediately signaled.

To send a Signal-With-Start in Python, use the [`start_workflow()`](https://python.temporal.io/temporalio.client.Client.html#start_workflow) method and pass the `start_signal` argument with the name of your Signal.

<div class="copycode-notice-container">
<a href="https://github.com/temporalio/documentation/blob/main/sample-apps/python/signal_your_workflow/signal_with_start_dacx.py">
View the source code in the context of the rest of the application code.
</a>{' '}

</div>

```python
from temporalio.client import Client
# ...
# ...
async def main():
client = await Client.connect("localhost:7233")
await client.start_workflow(
GreetingWorkflow.run,
id="your-signal-with-start-workflow",
task_queue="signal-tq",
start_signal="submit_greeting",
start_signal_args=["User Signal with Start"],
)
```




## Developing with Updates {#updates}
## Updates {#updates}

An [Update](/encyclopedia/workflow-message-passing#sending-updates) is a trackable request sent synchronously to a running Workflow Execution that can change the state and control the flow of a Workflow Execution, and return a result.
The sender of the request must wait until the update is at least accepted or rejected by a Worker, and will often opt to wait further to receive the value returned by the Update handler, or an exception indicating what went wrong. Update handlers can do arbitrarily long-running async operations (like signal handlers, and the main workflow method).
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