Did not find functions with language [python]. - Error

Question

Hello,

I have an Azure Function App running on a timer trigger, written in python. This function app uses the Consumption plan. I have been getting an exception for two months now that I am not entirely sure what it does. Here is the relevant information it gives me:

Message: Did not find functions with language [python].
Exception type: Microsoft.Azure.WebJobs.Script.HostInitializationException
Failed method: Microsoft.Azure.WebJobs.Script.Utility.VerifyFunctionsMatchSpecifiedLanguage
FormattedMessage: A host error has occurred during startup operation 'some-kind-of-id-here'.
Category: Host.Startup
LogLevel: Error

This exception seems to occur at any point in time, function running or idle. It can occur while the function is running but still not cause it to fail. I also believe it has little to do with the source code, as the source code has gone through complete rewrites but still this exception has been consistent. I have not been able to find anything online helpful with this error, just people saying to change config files to be what I already have had the whole time. If anyone has any experience with this issue or knows how to fix it, please let me know!

Thank you.

Answer 1

Hello Cameron !

Thank you for posting on Microsoft Learn Q&A.

The log means the host expected python because of your app setting but didn’t see any python functions when it indexed the app.

It is either a runtime issue so in your function app under configuration, you need to make sure that :

• FUNCTIONS_WORKER_RUNTIME = python
• FUNCTIONS_EXTENSION_VERSION = ~4

On Linux, the Stack shows Python (3.9/3.10/3.11/3.12 as supported). If you created the app as a .NET/Node app by mistake, the host won’t see Python functions. https://docs.azure.cn/en-us/azure-functions/errors-diagnostics/diagnostic-events/azfd0011

Or the host looks under /home/site/wwwroot for host.json and your function folders and each function for v1 model must have a folder with init and a function.json and for the v2 Python model you still need your files at the root, but not per-function function.json.