---
title: "Configure the Basic I/O function"
url: https://docs.catalyst.zoho.com/en/tutorials/hosted-login-app/python/configure-function/
description: "Create a simple Basic or React application using the features of Catalyst Hosted Authentication that provides user sign-up, application login, password reset, and implements sign-in using prevalent federated identity providers."
last_updated: 2025-11-19T15:07:41Z
service: All Services
type: tutorial
related_links:
  - name: "Basic I/O Functions"
    url: /en/serverless/help/functions/basic-io/
  - name: "Functions Directory Structure"
    url: /en/cli/v1/project-directory-structure/functions-directory
---

# Configure the Function

Now, we will begin coding the authorization portal application by configuring the function component.

The [function’s directory](https://docs.catalyst.zoho.com/en/cli/v1/project-directory-structure/functions-directory), (`functions/authorization_portal_function`), contains:

* The `main.py` main function file
* The `catalyst-config.json` configuration file
* Handler files
* [`requirements.txt`](https://docs.catalyst.zoho.com/en/cli/v1/project-directory-structure/functions-directory/#requirementstxt-file) file to mention any external libraries you might add

You will be adding code in the `main.py` file.

The Basic I/O function contains the following functionalities:

* The end-user's details will provided as a JSON input to the *Custom User Validation* function.
* The function is coded to implement a custom logic based upon which the end-user will either be authenticated or denied.

> **Note:** For the purpose of this tutorial, we have coded a logic for the Custom User Validation function where if the user's email provider is anyone other than Zylker Technology (`@zylker.com`) the end-user will not be able to sign up to the application. You can either use the same or code a logic of your preference.

Now, let’s begin coding the Basic I/O function.

Copy the code given below and paste it in the `main.py` file in the `functions/authorization_portal_function` directory of your project, and save the file. You can use any IDE of your choice to work with the application’s files.

> **Note:** Please go through the code in this section to make sure you fully understand it.

**main.py**

```javascript
import json
import zcatalyst_sdk
def handler(context, basicio):
catalyst_app = zcatalyst_sdk.initialize()
auth_service = catalyst_app.authentication()
request_details = auth_service.get_signup_validation_request(basicio)
if request_details:
if "@zylker.com" in request_details["user_details"]["email_id"]:
basicio.write(json.dumps({"status": "failure"})) 
//The user has failed authentication
else:                                                
//The actions that occur in the event of a successful authentication can be customized
basicio.write(
json.dumps(
{
"status": "success",
"user_details": {
"first_name": request_details["user_details"]["first_name"],
"last_name": request_details["user_details"]["last_name"],
"email_id": request_details["user_details"]["email_id"],
"role_identifier": "App User", 
//If you want to override the default role, you can specify the role id/name here.
'org_id': "orgId" 
//If you are providing the Org ID, make sure it is copied exactly from the console. 
},
}
)
)
context.close()

```

> **Note:** You can also use this [SDK](https://docs.catalyst.zoho.com/en/sdk/python/v1/cloud-scale/authentication/custom-user-validation/) to code your own custom logic instead of the one implemented above.

The function directory is now configured. We can now proceed to configuring the client directory.