Python V2: Azure function throwing NoneType errors with given sample code when accessing blob

Question

After setting up an azure function using VScode, Python V2 on Windows & using quickstart directions, and sample from here: https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-storage-blob-input?tabs=python-v2%2Cin-process&pivots=programming-language-python

Additionally I also set it up within a trigger to test:

@app.timer_trigger(schedule="*/5 * * * * *", arg_name="myTimer", run_on_startup=True,
              use_monitor=False) 
@app.blob_input(arg_name="inputblob",
                path="samples/test.txt",
                connection="AzureWebJobsStorage")
@app.blob_output(arg_name="outputblob",
                path="newblob/test.txt",
                connection="AzureWebJobsStorage")
#def TimerTrigger(myTimer: func.TimerRequest, inputblob: str, outputblob: func.Out[str]) -> None:
def TimerTrigger(myTimer, inputblob, outputblob) :
    
    if myTimer.past_due:
        logging.info('The timer is past due!')

    logging.info('Python timer trigger function executed.')
    logging.info(f'Python Queue trigger function processed {len(inputblob)} bytes')
    outputblob.set(inputblob)
    return "ok"

Consistently getting errors which are variations of:

Executed 'Functions.TimerTrigger' (Failed, Id=b1ab178c-e66a-4bbe-9ee6-bc9dc9241120, Duration=15ms) [2023-08-15T19:59:55.023Z] System.Private.CoreLib: Exception while executing function: Functions.TimerTrigger. System.Private.CoreLib: Result: Failure Exception: TypeError: object of type 'NoneType' has no len() Stack: File "C:\Users\T8\AppData\Roaming\nvm\v16.18.0\node_modules\azure-functions-core-tools\bin\workers\python\3.11\WINDOWS\X64\azure_functions_worker\dispatcher.py", line 479, in _handle__invocation_request call_result = await self._loop.run_in_executor( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\T8\AppData\Local\Programs\Python\Python311\Lib\concurrent\futures\thread.py", line 58, in run result = self.fn(*self.args, **self.kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\T8\AppData\Roaming\nvm\v16.18.0\node_modules\azure-functions-core-tools\bin\workers\python\3.11\WINDOWS\X64\azure_functions_worker\dispatcher.py", line 752, in _run_sync_func return ExtensionManager.get_sync_invocation_wrapper(context, ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\T8\AppData\Roaming\nvm\v16.18.0\node_modules\azure-functions-core-tools\bin\workers\python\3.11\WINDOWS\X64\azure_functions_worker\extension.py", line 215, in _raw_invocation_wrapper result = function(**args) ^^^^^^^^^^^^^^^^ File "C:\Users\T8\source\repos\Q8Utilities\filefuncapp\function_app.py", line 50, in TimerTrigger logging.info(f'Python Queue trigger function processed {len(inputblob)} bytes')

Expecting this should just run. Updated to Python 3.11, same result.

I've tried providing the data_type parameter to the blob_input() argument list. Same result

I've also tried using InputStream for the blob & using the read() method. Same error. def HttpTriggerFile(req: func.HttpRequest, obj: func.InputStream) -> func.HttpResponse: logging.info('Python HTTP trigger function processed a request.') logging.info(f'Python HTTP-triggered function processed: {obj.read()}')

What am I missing? Is the provided code incorrect? Some kind of setup issue?

Thanks

P Sampath · Accepted Answer · 2023-08-16 13:12:08Z

1

Encountering a NoneType error when accessing the blob. The error occurs when a variable or object that you expect to contain a value (not None) actually contains None.

The Blob Trigger function listens for changes in a blob container and processes the input blob by copying its content to an output blob and runs on a scheduled basis and logs the execution time.
I tried below code :

import datetime
import logging
import azure.functions as func

app = func.FunctionApp()

# Blob Trigger Function
@app.function_name(name="BlobOutput1")
@app.route(route="file")
@app.blob_input(arg_name="inputblob",
                path="samples/test.txt",
                connection="AzureWebJobsStorage")
@app.blob_output(arg_name="outputblob",
                path="newblob/test.txt",
                connection="AzureWebJobsStorage")
def main(req: func.HttpRequest, inputblob: str, outputblob: func.Out[str]):
    logging.info(f'Python Queue trigger function processed {len(inputblob)} bytes')
    outputblob.set(inputblob)
    return "ok"

# Timer Trigger Function
@app.schedule(schedule="*/5 * * * * *", arg_name="myTimer", run_on_startup=True, use_monitor=False) 
def TimerTrigger(myTimer: func.TimerRequest) -> None:
    utc_timestamp = datetime.datetime.utcnow().replace(
        tzinfo=datetime.timezone.utc).isoformat()

    if myTimer.past_due:
        logging.info('The timer is past due!')

    logging.info('Python timer trigger function ran at %s', utc_timestamp)

Output:

enter image description here

edited Aug 16, 2023 at 13:12

answered Aug 16, 2023 at 5:35

P Sampath

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4 Comments

Tyrone Jones Over a year ago

Thanks. Are you able to try the blob code within the timer trigger ? Just need to confirm, as I used your example and still get the error when "BlobOutput1" is run with an httpRequest. The code provided looks essentially the same as mine, which I think is part of the puzzle: "If the code is the same, what in the environment could cause the difference in runtime behavior ?"

P Sampath Over a year ago

Yes ,able to use this blob code within the timer trigger. selected v2 and timer trigger in the path give container/blobname and in local.setting.json place connectionstring in "AzureWebJobsStorage": " DefaultEndpointsProtocot " - Python 3.10.9

P Sampath Over a year ago

path as sam/hello.txt a sample hello.txt upload with some content and sam2/hello2.txt a sample hello.txt upload with no content Image

Tyrone Jones Over a year ago

Yeah, still getting the same error. Must be some issue in the azure functions environment manifesting itself here.

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