Azure Pipelines - Output variable from python script file to pipeline variable - azure-devops

Question

I've tried several articles and threads from Stackoverflow but can't seem to get anywhere. I am trying to take a variable from a .py file which is called in a YAML step and set that variable globally to be used.
In my .py file i have
print(f'##vso[task.setvariable variable=AMLPipelineId;isOutput=true]{pipelineId}')
Then in my YAML pipeline step i have
- task: AzurePowerShell#5
displayName: 'Run AML Pipeline'
inputs:
azureSubscription: '$(azureSubscription)'
ScriptType: 'InlineScript'
name: AmlPipeline
azurePowerShellVersion: 'LatestVersion'
pwsh: true
Inline: |
$username = "$(ARM_CLIENT_ID)"
$password = "$(ARM_CLIENT_SECRET)"
$tenantId = "$(ARM_TENANT_ID)"
python $(Pipeline.Workspace)/AML_Pipeline/build_aml_pipeline.py --wsName $(wsName) --resourceGroup $(ResourceGroupName) --subscriptionId $(subId)
$MLPipelineId = $AmlPipeline.AMLPipelineId
But it seems like this variable is empty. I know there are other ways of using the "set variable" but this is my latest attempt i.e. something like print('##vso[task.setvariable variable=version;]%s' % (version))
My current approach i followed: https://learn.microsoft.com/en-us/azure/devops/pipelines/process/variables?view=azure-devops&tabs=yaml%2Cbatch

Answer 1

You don't need isOutput=true - that's only needed for referencing variables between different jobs or stages.
"You cannot use the variable in the step that it is defined." - split that script into two steps: one that runs your .py file, second one that uses the newly defined variable.

Answer 2

I used print('##vso[task.setvariable variable=<Variable-in-Pipeline]+<output-variable>')
Variable-in-Pipeline // the given name should be used in Azure Devops pipeline and should be added to pipeline variables as an empty string

Answer 3

A very minimal example for everyone struggling with this. The documentation is kind of lacking on this for my taste. As #qbik said, dont set and use the variable in the same step, make it seperate steps.
set_variable.py
if __name__ == '__main__':
# set name of the variable
name = 'COLOR'
# set value of the variable
value = 'red'
# set variable
print(f'##vso[task.setvariable variable={name};]{value}')
azure-pipelines.yml
trigger:
- main
pool:
vmImage: ubuntu-latest
steps:
- task: UsePythonVersion#0
inputs:
versionSpec: '3.9'
displayName: 'Use Python 3.9'
# run the script to set the variable
- task: PythonScript#0
inputs:
scriptSource: filePath
scriptPath: set_variable.py
# now you can use the variable in the next step
- bash: echo my favorite color is: $(COLOR)
Now you can technically do all kinds of cool stuff in python, then set, and reference the variables in the following steps. In my case I have to extract specific package version numbers from a JSON/YAML file based on an id that is set earlier in the pipeline and parse the information as an args for a docker build. Hope that helps other people stumbling across this answer looking for a minimal working example :)