Drop Python 3.9 from CI pipelines, pin minimum to 3.10 (#3461)

* Initial plan

* Drop Python 3.9 from eng pipelines, pin min to 3.10

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Co-authored-by: msyyc <70930885+msyyc@users.noreply.github.com>

* Update drop-python-39-pipeline-2026-4-28-5-30-0.md

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: msyyc <70930885+msyyc@users.noreply.github.com>
Co-authored-by: Yuchao Yan <yuchaoyan@microsoft.com>

Author: Copilot

.chronus/changes/drop-python-39-pipeline-2026-4-28-5-30-0.md

@@ -0,0 +1,8 @@
+---
+changeKind: internal
+packages:
+  - "@autorest/python"
+  - "@azure-tools/typespec-python"
+---
+
+Drop Python 3.9 from CI pipelines and pin the minimum Python version to 3.10

eng/pipelines/ci.yml

@@ -49,20 +49,15 @@ jobs:
 
     strategy:
       matrix:
-        Linux_Python3.9:
+        Linux_Python3.10:
           OSName: "Linux"
           Pool: ${{ variables.LINUXPOOL }}
           OSVmImage: ${{ variables.LINUXVMIMAGE}}
-          PythonVersion: "3.9"
-        Windows_Python3.9:
+          PythonVersion: "3.10"
+        Windows_Python3.10:
           OSName: "Windows"
           Pool: ${{ variables.WINDOWSPOOL }}
           OSVmImage: ${{ variables.WINDOWSVMIMAGE}}
-          PythonVersion: "3.9"
-        Linux_Python3.10:
-          OSName: "Linux"
-          Pool: ${{ variables.LINUXPOOL }}
-          OSVmImage: ${{ variables.LINUXVMIMAGE}}
           PythonVersion: "3.10"
         Linux_Python3.11:
           OSName: "Linux"
@@ -140,20 +135,15 @@ jobs:
 
     strategy:
       matrix:
-        Linux_Python3.9:
+        Linux_Python310:
           OSName: "Linux"
           Pool: ${{ variables.LINUXPOOL }}
           OSVmImage: ${{ variables.LINUXVMIMAGE}}
-          PythonVersion: "3.9"
-        Windows_Python3.9:
+          PythonVersion: "3.10"
+        Windows_Python310:
           OSName: "Windows"
           Pool: ${{ variables.WINDOWSPOOL }}
           OSVmImage: ${{ variables.WINDOWSVMIMAGE}}
-          PythonVersion: "3.9"
-        Linux_Python310:
-          OSName: "Linux"
-          Pool: ${{ variables.LINUXPOOL }}
-          OSVmImage: ${{ variables.LINUXVMIMAGE}}
           PythonVersion: "3.10"
         Linux_Python311:
           OSName: "Linux"

eng/pipelines/generated-code-checks-template.yml

@@ -10,7 +10,7 @@ steps:
     - script: npm run test -- --env=lint --flavor=${{ parameters.folderName }}
       displayName: Lint ${{ parameters.folderName }} - Python $(PythonVersion)
       workingDirectory: $(Build.SourcesDirectory)/autorest.python/packages/${{parameters.package}}
-      condition: and(eq(variables['PythonVersion'], '3.9'), or(contains('${{ parameters.folderName }}', 'version-tolerant'), eq('${{parameters.package}}', 'typespec-python')))
+      condition: and(eq(variables['PythonVersion'], '3.10'), or(contains('${{ parameters.folderName }}', 'version-tolerant'), eq('${{parameters.package}}', 'typespec-python')))
 
     - script: npm run test -- --env=mypy --flavor=${{ parameters.folderName }}
       displayName: Mypy ${{ parameters.folderName }} - Python $(PythonVersion)

eng/pipelines/preview.yml

@@ -76,9 +76,9 @@ extends:
           versionSpec: 3.11
     SdkInitializationSteps:
     - task: UsePythonVersion@0
-      displayName: "Use Python 3.9"
+      displayName: "Use Python 3.10"
       inputs:
-          versionSpec: 3.9
+          versionSpec: 3.10
     - script: |
         echo "npm install -g @azure-tools/typespec-client-generator-cli"
         npm install -g @azure-tools/typespec-client-generator-cli

eng/pipelines/publish-dev-release.yml

@@ -3,7 +3,7 @@ pr: none
 
 variables:
   NodeVersion: "20.x"
-  PythonVersion: "3.9"
+  PythonVersion: "3.10"
   TestFolder: "$(Build.SourcesDirectory)/test/"
 
 pool:
@@ -16,9 +16,9 @@ steps:
       versionSpec: "$(NodeVersion)"
 
   - task: UsePythonVersion@0
-    displayName: "Use Python 3.9"
+    displayName: "Use Python 3.10"
     inputs:
-      versionSpec: 3.9
+      versionSpec: 3.10
 
   - script: |
       cd $(Build.SourcesDirectory)

eng/scripts/run_pylint.py

@@ -38,7 +38,7 @@ def _single_dir_pylint(mod):
                 "--load-plugins=pylint_guidelines_checker",
                 "--output-format=parseable",
                 "--recursive=y",
-                "--py-version=3.9",
+                "--py-version=3.10",
                 str(inner_class.absolute()),
             ]
         )
@@ -49,7 +49,7 @@ def _single_dir_pylint(mod):
 
 
 if __name__ == "__main__":
-    if sys.version_info >= (3, 10, 0):
-        # only run pylint with python 3.9
+    if sys.version_info >= (3, 11, 0) or sys.version_info < (3, 10, 0):
+        # only run pylint with python 3.10
         sys.exit(0)
     run_check("pylint", _single_dir_pylint, "Pylint")