---
title: "system.sfc.setVariable"
description: "Sets a variable inside a currently running chart."
---

# system.sfc.setVariable

> Sets a variable inside a currently running chart.

This function is used in **Python Scripting**.

## Description
Sets a variable inside a currently running [SFC chart](../../../ignition-modules/sequential-function-charts/SFC-basics/SFC-basics.md).

## Client Permission Restrictions
[Permission Type](../../../ignition-modules/vision/vision-project-properties/vision-project-properties.md#vision-permissions-properties): SFC Management

Client access to this scripting function is blocked to users that do not meet the role/zone requirements for the above permission type. This function is unaffected when run in the Gateway scope.

## Syntax
`system.sfc.setVariable(instanceId, [stepId], variableName, variableValue)`

### Parameters
Type | Parameter | Description 
------- | ------- | ------
String| `instanceId` | The instance identifier of the chart.
String| `stepId` | The id for a step inside of a chart. If omitted the function will target a chart scoped variable. [optional]
String| `variableName` | The name of the variable to set.
Object| `variableValue` | The value for the variable to be set to.

### Returns
Nothing
### Scope
Gateway, Vision Client, Perspective Session

:::note
Omitting the **stepId** parameter will cause the function to target a chart scoped variable. If the variable is persistent to the whole chart, or used in multiple different steps, then this parameter should be omitted.

If a stepId parameter is used, then the function will target a step scoped variable. The step associated with the stepId must be the currently active step.
:::

## Code Examples
```python title="Code Snippet"
# The following passes the chart instance ID and step ID to a client message Handler. The message handler can then wait
# for user input, and then write back to the step variables. 
 
# The example assumes there is a chart scoped variable called confirmEndchart, and a step scoped variable called "messageSent".
 
# Get the instanceId of the current chart
chartID = chart.get("instanceId")
         
# Get the id of the step
stepID = step.get("id")
         
# Create a payload to pass to the client.
# Include the instanceId and stepId so the script from the message handler knows which
# chart and step to write to
payload = {"chartID" : chartID, "stepID" : stepID}
         
# Send the message
system.util.sendMessage(project="SFC", messageHandler="SFCMessage", payload=payload)  
     
############   
 
# The following script would be placed on a client message handler. This receives the payload,
# and sets a variable on either the chart or step depending on user selection
 
# Read items out of the payload
id = payload['chartID']
stepId = payload['stepID']
     
# Ask the user to end the chart
if system.vision.showConfirm("Would you like to end the process"):
    #If yes, end the chart. confirmEndChart is chart scoped, so only 3 parameters are passed
    system.sfc.setVariable(id, "confirmEndChart", True)
else:
    #If no, reset the step.messageSent variable so that the user will be prompted again
    #messageSent is step scoped, so 4 parameters are passed
    system.sfc.setVariable(id, stepId, "messageSent", False)
```