Runs custom Python code. Useful for logic not covered by existing blocks. Python code block

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Overview

The Python code block allows you to write Python code to extend your blueprint’s functionality. Use it to perform custom data processing, calculations, API integrations, or any other logic that requires Python programming capabilities.

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Common use cases

  • Custom data processing and transformations
  • Complex calculations and mathematical operations
  • API integrations with external services
  • File manipulation and data parsing

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How it works

  1. Code execution: Write Python code in the block’s code editor.
  2. Variable access: Access state variables, environment variables, and preinstalled libraries.
  3. Output generation: Use set_output() to return values to subsequent blocks.
  4. Error handling: Handle exceptions and provide meaningful error messages. If an error occurs, access the error message in the next block using @{message}.
  5. Error exit condition: Raise an Exception to trigger the Error exit condition and route to error handling blocks.
The block provides a full Python environment with access to state variables, execution environment variables, and preinstalled libraries.

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Examples

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Calculate average from list

This example shows how to return a value from the Python code block. It calculates the average of a list of numbers and returns the result to the next block by using the set_output function. Blueprint flow:
  1. UI Trigger → User provides list of numbers
  2. Python code → Calculates average of numbers
  3. Set state → Stores result in state variable
def calculate_mean(numbers):
    return sum(numbers) / len(numbers)

average = calculate_mean(state["numbers"])
set_output(average)
Python code block example

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Error handling with exceptions

You can trigger the Error exit condition by raising an Exception in your Python code. This allows you to route to error handling blocks when specific conditions are met. Example: 
# Validate user input and raise exception if invalid
user_age = state.get("age", 0)

if user_age < 0 or user_age > 120:
    raise Exception("Invalid age: Age must be between 0 and 120")

if not state.get("email"):
    raise Exception("Missing required field: Email address")

# Process valid data
set_output({"status": "valid", "age": user_age})
When an Exception occurs, the Python code block exits with the Error condition, allowing you to route to error handling blocks in your blueprint. You can access the error message in the next block by referencing the @{message} variable.

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Available variables and libraries

Python code block can access the following global variables and libraries:

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Return values from the Python code block

To return a value from a Python code block and store it in the result execution environment variable, you must use the set_output function. Anything that runs in the block but is not returned in the set_output function does not get passed to the next block.

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Fields

NameTypeControlDefaultDescriptionOptionsValidation
CodeCodeTextarea-The code to be executed.--

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End states

Below are the possible end states of the block call.
NameFieldTypeDescription
Success-successThe event handler execution was successful.
Error-errorThe event handler execution wasn’t successful.
Access the output of a Python code block using the @{result} variable in the block that follows it in a blueprint. The output contains whatever value was passed to the set_output() function. Access the error message of a Python code block using the @{message} variable in the block that follows it in a blueprint. The error message contains whatever value was passed to the raise Exception function.