Azure App Service Python Version Upgrade

Question

Azure App Service Python Version Upgrade

Jester Bojorque 250

Hello,

I just want to confirm if my way of testing is enough to confirm that the app service we use is ok to upgrade to the latest python version:

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I dont have python knowledge or azure cloud I am just learning through browsing the internet.

Currently, I cannot test it in the azure since we do not have an instance of staging, dev or deployment slot where I can test this before updating the python version of our web app in production on Azure.

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I am open for any recommendation or tips where I can assure the compatibility of the current service to the new python version.

It is currently on 3.10 and im planning to upgrade it to 3.11 atleast.

Thank you very much!

Shree Hima Bindu Maganti 6,880 Reputation points Microsoft External Staff Moderator

2026-04-05T15:25:45.8966667+00:00

Hi @Jester Bojorque
Your current approach of creating a virtual environment and running pip install -r requirements.txt is a good initial compatibility check, but it is not sufficient to safely validate upgrading Python from 3.10 to 3.11 in Azure App Service, because it only verifies that dependencies install locally and does not account for runtime behavior, startup configuration, or platform differences in Azure. Since you do not have a staging or dev environment, the recommended and supported approach is to use deployment slots, which allow you to create a staging environment within the same App Service, test the new Python version, and then perform a safe swap to production with no downtime; alternatively, you can clone your existing App Service into a separate test app with the same configuration and validate there before upgrading. You should also ensure that all your dependencies explicitly support Python 3.11 and monitor application logs after deployment to confirm there are no runtime errors. Microsoft guidance strongly recommends testing runtime changes in a staging environment before applying them to production
https://learn.microsoft.com/en-us/azure/app-service/deploy-staging-slots?tabs=portal
https://learn.microsoft.com/en-us/azure/app-service/configure-language-python
Let me know if you have any further assistance needed.
Jester Bojorque 250 Reputation points

2026-04-07T02:20:48.5333333+00:00

Hello @Shree Hima Bindu Maganti

Thank you for your response.

As much as possible I do not want to perform any testing in Azure itself since I am not knowledgeable to Cloud. I am mainly relying to internet information and this community.

I did the virtual environment and it returns issues with libraries and dependencies:

so to double check I did a separate testing but still locally. I was able to get a docker data of our frontend and backend apps. I ran those data and tried to update the dackerfile to python:3.11-slim and it seems to be working as i did not see any errors or issues in the result. I can access the web portals via localhost and basic functions works.

So my question is why the venv result fails and the docker setup worked?

And since the web app worked from the docker setup(upgraded from 3.10 to 3.11) is it safe to say that I can just update the stack settings of our backend to 3.11?

Thank you.

1 answer

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Shree Hima Bindu Maganti 6,880 Reputation points Microsoft External Staff Moderator

2026-04-05T15:25:45.8966667+00:00

Hi @Jester Bojorque
Your current approach of creating a virtual environment and running pip install -r requirements.txt is a good initial compatibility check, but it is not sufficient to safely validate upgrading Python from 3.10 to 3.11 in Azure App Service, because it only verifies that dependencies install locally and does not account for runtime behavior, startup configuration, or platform differences in Azure. Since you do not have a staging or dev environment, the recommended and supported approach is to use deployment slots, which allow you to create a staging environment within the same App Service, test the new Python version, and then perform a safe swap to production with no downtime; alternatively, you can clone your existing App Service into a separate test app with the same configuration and validate there before upgrading. You should also ensure that all your dependencies explicitly support Python 3.11 and monitor application logs after deployment to confirm there are no runtime errors. Microsoft guidance strongly recommends testing runtime changes in a staging environment before applying them to production
https://learn.microsoft.com/en-us/azure/app-service/deploy-staging-slots?tabs=portal
https://learn.microsoft.com/en-us/azure/app-service/configure-language-python
Let me know if you have any further assistance needed.
Jester Bojorque 250 Reputation points

2026-04-07T02:20:48.5333333+00:00

Hello @Shree Hima Bindu Maganti

Thank you for your response.

As much as possible I do not want to perform any testing in Azure itself since I am not knowledgeable to Cloud. I am mainly relying to internet information and this community.

I did the virtual environment and it returns issues with libraries and dependencies:

so to double check I did a separate testing but still locally. I was able to get a docker data of our frontend and backend apps. I ran those data and tried to update the dackerfile to python:3.11-slim and it seems to be working as i did not see any errors or issues in the result. I can access the web portals via localhost and basic functions works.

So my question is why the venv result fails and the docker setup worked?

And since the web app worked from the docker setup(upgraded from 3.10 to 3.11) is it safe to say that I can just update the stack settings of our backend to 3.11?

Thank you.

Answer 1

The local virtual environment test is a good start, but by itself it doesn’t fully guarantee that the Azure App Service will work after a Python upgrade. Compatibility depends on two things:

The Python version your code and dependencies support.
The Python runtime versions that Azure App Service supports and how the app is configured there.

From the context:

Azure App Service lets the Python version be configured either in the portal (Stack/Version) or via linuxFxVersion using Azure CLI.
Outdated runtimes are eventually deprecated and removed from the portal, but apps already using them continue to run until the runtime is fully removed.

To increase confidence before changing production:

Confirm the target version is supported in App Service
Use Azure CLI to list supported Python runtimes for Linux:
```
   az webapp list-runtimes --os linux | grep PYTHON
```
This shows which exact PYTHON|x.y values are available for your web app.
Match local tests to the Azure runtime
When creating the local virtual environment, use the same major/minor version that App Service will use (for example, 3.11.x). Install all dependencies with pip install -r requirements.txt and run the application’s own tests or a basic startup test (for example, run the web app locally) to ensure imports and startup succeed.

Plan the change in App Service
For Linux apps, the Python version is controlled by linuxFxVersion. You can view or set it with Azure CLI:

   az webapp config show \
     --resource-group <resource-group-name> \
     --name <app-name> \
     --query linuxFxVersion
   
   az webapp config set \
     --resource-group <resource-group-name> \
     --name <app-name> \
     --linux-fx-version "PYTHON|3.11"

Replace names as appropriate. This aligns the app with the Python version you tested locally.

Use a non‑production slot when possible
If deployment slots are added later, first set the new Python version on a staging slot, deploy the app there, verify it runs correctly, and then swap the slot into production. This minimizes downtime and risk.
Be aware of deprecation timelines
Azure Advisor already recommends upgrading apps off older Python versions as support ends. Keeping the app on a supported version (for example, moving from 3.10 to a newer supported version) avoids losing security updates and support.

In summary, the local venv test is useful but should be combined with checking supported runtimes in App Service and, ideally, validating on a staging slot before changing production. The actual upgrade in Azure is done by updating the linuxFxVersion/stack version to the desired supported Python version.

References:

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Azure App Service Python Version Upgrade

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