Trying to trigger an url from azure functions using python, errored saying "without a $return binding returned a non-None value"

Question

Below is the code,

import logging
import json 
import urllib.request
import urllib.parse
import azure.functions as func


def main(myblob: func.InputStream):
    logging.info(f"Python blob trigger function processed blob \n"
                 f"Name: {myblob.name}\n"
                 f"Blob Size: {myblob.length} bytes")
    response = urllib.request.urlopen("http://example.com:5000/processing")
    return {
        'statusCode': 200,
        'body': json.dumps(response.read().decode('utf-8'))
    }

Error: Result: Failure Exception: RuntimeError: function 'abc' without a $return binding returned a non-None value Stack: File "/azure-functions-host/workers/python/3.7/LINUX/X64/azure_functions_worker/dispatcher.py", line 341, in _handle__invocation_request f'function {fi.name!r} without a $return binding '. The same code works in lambda.. Please help me in debugging in azure functions.

function.json

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "name": "myblob",
      "type": "blobTrigger",
      "direction": "in",
      "path": "sourcemetadata/{name}",
      "connection": "AzureWebJobsStorage"
    }
  ]
}

@JimXu If i have folder structure inside container .. Container name : abc Folder name : example... How can i define path in function.json? ---- "path": "abc/example/{name}.csv", — Raphael Titus
– Raphael Titus, Commented Jul 13, 2020 at 8:33

Jim Xu · Accepted Answer · 2020-07-09 06:39:45Z

7

In the Azure function, if you use return in the function app code, it means that you want to use output binding. But you do not define it in function.json. Please define it. For more details, please refer to here and here

For example

I use process blob with blob trigger and send message to azure queue with queue output binding

function.json

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "name": "myblob",
      "type": "blobTrigger",
      "direction": "in",
      "path": "test/{name}.csv",
      "connection": "AzureWebJobsStorage"
    },
    {
      "name": "$return",
      "direction": "out",
      "type": "queue",
      "queueName": "outqueue",
      "connection": "AzureWebJobsStorage"
    }
  ]
}

Code

async def main(myblob: func.InputStream) :
    
    logging.info(f"Python blob trigger function processed blob \n"
                 f"Name: {myblob.name}\n")
    return "OK"

answered Jul 9, 2020 at 6:39

Jim Xu

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3 Comments

Raphael Titus Over a year ago

Thanks a lot Jim Xu for clarifying how "return" works with azure functions. I have configured the same and it works well.

Raphael Titus Over a year ago

If i have folder structure inside container .. Container name : abc Folder name : example... How can i define path in function.json? ---- "path": "abc/example/{name}.csv",

Jim Xu Over a year ago

Yes you can define path like that

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