Add custom functionality via Python code

This is a feature of the external Python module (see Setup). It allows you to write custom functions in Python, expose them via FastAPI, and call them from the special ExtCallPythonModule node in OmniChain.

To create a custom function, you need to:

• Add a new folder inside the custom_modules folder in the root of the project of the external Python module

• Add an __init__.py file inside the new folder

• Expose a setup function to receive the main FastAPI app and add your custom functions to it

Example

This is a basic example of the __init__.py file. A similar example is available for copy-pasting in the custom_modules folder of the external Python module. To understand this example, you should familiarize yourself with the FastAPI (opens in a new tab) and Pydantic (opens in a new tab) libraries.

Feel free to add more files inside your module(s) and also to install and import any dependencies you need. Just make sure you don't cause conflicts that break the base project.

from fastapi import FastAPI
from pydantic import BaseModel
 
 
class ExampleModel(BaseModel):
    """
    An example model for the example module.
    """
 
    custom_parameter: str | None
 
 
def setup(app: FastAPI):
    """
    The setup function for the example module.
    """
 
    def echo(data: ExampleModel | None = None):
        """
        A simple route that echoes back the custom parameter.
        """
 
        custom_parameter = data.custom_parameter if data else None
 
        return {"message": custom_parameter if custom_parameter else "Hello there!"}
 
    # Add the hello route to the app
    app.post("/example/echo")(echo)

Note: Do not delete or rename the example in the project or it will cause conflicts with git.