Write output to Blob in Azure Functions

Question

I am learning to use Azure functions. So, I might sound stupid. I am writing a timer trigger function which runs every 1 minute and adds two number and writes to a file. This works fine since I can write the output to the file on the local server.

As a second step, I wanted to write the output to the blob. Below is the code:

import datetime
import logging  
import azure.functions as func

a=4
b=5
sum=a+b
file_name= open("sum.txt","w+")


def main(mytimer: func.TimerRequest, outputBlob: func.Out[str]) -> None:
    utc_timestamp = datetime.datetime.utcnow().replace(
        tzinfo=datetime.timezone.utc).isoformat()
    if mytimer.past_due:
        global sum
        global file_name
        print("sum:", sum)
        logging.info('The sum has been calculated!')



    logging.info(sum)
    logging.info('Python timer trigger function ran at %s', utc_timestamp)
    with open("sum.txt", "a") as file_name:
        file_name.seek(0)
        file_name.write("\n")
        file_name.write("Sum: %s" % sum)

    outputBlob.set(file_name)

However, when I run the function I get the below error:

[10/02/2020 14:06:00] Executed 'Functions.CalcPayment' (Failed, Id=547f7a3d-03b4-4a02-98e7-f4bfb73e6f5e)
[10/02/2020 14:06:00] System.Private.CoreLib: Exception while executing function: Functions.CalcPayment. System.Private.CoreLib: Result: Failure
[10/02/2020 14:06:00] Exception: TypeError: unable to encode outgoing TypedData: unsupported type "<class 'azure_functions_worker.bindings.generic.GenericBinding'>" for Python type "int"
[10/02/2020 14:06:00] Stack:   File "/usr/local/Cellar/azure-functions-core-tools@3/3.0.2106/workers/python/3.7/OSX/X64/azure_functions_worker/dispatcher.py", line 330, in _handle__invocation_request
[10/02/2020 14:06:00]     pytype=out_type_info.pytype)
[10/02/2020 14:06:00]   File "/usr/local/Cellar/azure-functions-core-tools@3/3.0.2106/workers/python/3.7/OSX/X64/azure_functions_worker/bindings/meta.py", line 83, in to_outgoing_proto
[10/02/2020 14:06:00]     f'unable to encode outgoing TypedData: '
[10/02/2020 14:06:00] .

Answer 1

you dont need to have a file to write to, just create a string that makes sense in your case and push it to the output variable. You can use this sample as a starting point.

Answer 2

Ok. So the issue was very simple. I had to convert the sum to string and write to the blob and everything worked. Thanks !!