Fix Windows python3 availability in container build paths.

Preserve container PATH during Windows docker-run steps and create/verify a python3 alias from Scoop Python so Quarto/Jupyter kernels that invoke python3 work reliably in both install-time and final verification checks.

.github/workflows/book-build-baremetal.yml

@@ -513,6 +513,19 @@ jobs:
           }
           Write-Output "📊 Python version: $pythonVersion"
 
+          $pyExe = (python -c "import sys; print(sys.executable)").Trim()
+          $pyDir = Split-Path $pyExe -Parent
+          $py3Exe = Join-Path $pyDir "python3.exe"
+          if (-not (Test-Path $py3Exe)) {
+            Copy-Item $pyExe $py3Exe -Force
+          }
+          $python3Version = python3 --version
+          if ($LASTEXITCODE -ne 0) {
+            Write-Error "❌ python3 --version failed with exit code $LASTEXITCODE"
+            exit 1
+          }
+          Write-Output "📊 Python3 version: $python3Version"
+
           # Verify we got Python 3.13
           if ($pythonVersion -notmatch "3\.13") {
             Write-Error "❌ Expected Python 3.13, got: $pythonVersion"
@@ -1175,6 +1188,19 @@ jobs:
           Write-Output "  $out"
           Write-Output "✅ Python verified"
 
+      - name: ✅ Verify Python3 (Windows)
+        if: matrix.enabled && runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $cmd = Get-Command python3 -ErrorAction SilentlyContinue
+          if (-not $cmd) { Write-Error "❌ Python3 not found"; exit 1 }
+          Write-Output "Resolved: $($cmd.Source)"
+          $out = & python3 --version 2>&1 | Select-Object -First 1
+          $exitCode = if ($null -eq $LASTEXITCODE) { if ($?) { 0 } else { 1 } } else { [int]$LASTEXITCODE }
+          if ($exitCode -ne 0) { Write-Error "❌ Python3 check failed (exit $exitCode)"; exit 1 }
+          Write-Output "  $out"
+          Write-Output "✅ Python3 verified"
+
       - name: ✅ Verify R (Windows)
         if: matrix.enabled && runner.os == 'Windows'
         shell: pwsh

.github/workflows/book-build-container.yml

@@ -392,7 +392,6 @@ jobs:
         run: |
           Write-Host "🔨 Building ${{ matrix.format_name }} on Windows container..."
           docker run --rm -v "$($PWD.Path):C:\workspace" -w "C:\workspace\book\quarto" ${{ env.CONTAINER_IMAGE }} pwsh -NoLogo -Command "
-            `$env:PATH = [Environment]::GetEnvironmentVariable('PATH','Machine')
             if (Test-Path '_quarto.yml') { Remove-Item '_quarto.yml' -Force }
             Copy-Item 'config\${{ matrix.config }}' '_quarto.yml' -Force
             quarto render --to ${{ matrix.render_target }} --output-dir '${{ matrix.output_dir }}'
@@ -440,7 +439,6 @@ jobs:
         run: |
           Write-Host "🔨 Compressing PDF on Windows container..."
           docker run --rm -v "$($PWD.Path):C:\workspace" -w "C:\workspace\book\quarto\${{ matrix.output_dir }}" ${{ env.CONTAINER_IMAGE }} pwsh -NoLogo -Command "
-            `$env:PATH = [Environment]::GetEnvironmentVariable('PATH','Machine')
             if (Test-Path 'Machine-Learning-Systems.pdf') {
               Write-Host '📉 Compressing PDF with professional compression tool...'
               Write-Host '🔍 DEBUG: Current directory:'
@@ -516,7 +514,6 @@ jobs:
         run: |
           Write-Host "🔨 Compressing EPUB on Windows container..."
           docker run --rm -v "$($PWD.Path):C:\workspace" -w "C:\workspace\book\quarto\${{ matrix.output_dir }}" ${{ env.CONTAINER_IMAGE }} pwsh -NoLogo -Command "
-            `$env:PATH = [Environment]::GetEnvironmentVariable('PATH','Machine')
             if (Test-Path 'Machine-Learning-Systems.epub') {
               Write-Host '📚 Compressing EPUB with optimized compression tool...'
               Write-Host '🔍 DEBUG: Current directory:'

book/docker/windows/Dockerfile

@@ -227,7 +227,19 @@ RUN Write-Host '=== STARTING PYTHON INSTALLATION ===' ; `
         Write-Host "❌ Python install failed: version check exited $LASTEXITCODE" ; `
         exit 1 ; `
     } ; `
+    $pyExe = (python -c "import sys; print(sys.executable)").Trim() ; `
+    $pyDir = Split-Path $pyExe -Parent ; `
+    $py3Exe = Join-Path $pyDir 'python3.exe' ; `
+    if (-not (Test-Path $py3Exe)) { `
+        Copy-Item $pyExe $py3Exe -Force ; `
+    } ; `
+    $pv3 = python3 --version ; `
+    if ($LASTEXITCODE -ne 0) { `
+        Write-Host "❌ Python install failed: python3 alias check exited $LASTEXITCODE" ; `
+        exit 1 ; `
+    } ; `
     Write-Host "📦 Python installed: $pv" ; `
+    Write-Host "📦 Python3 alias verified: $pv3" ; `
     Write-Host '✅ Python installation complete'
 
 # ------------------------------------------------------------
@@ -382,6 +394,16 @@ RUN Write-Host '=== VERIFY: Python ===' ; `
     Write-Host "  $out" ; `
     Write-Host '✅ Python verified'
 
+RUN Write-Host '=== VERIFY: Python3 ===' ; `
+    $cmd = Get-Command python3 -ErrorAction SilentlyContinue ; `
+    if (-not $cmd) { Write-Host "❌ Python3 FAILED: command not found"; exit 1 } ; `
+    Write-Host "Resolved: $($cmd.Source)" ; `
+    $out = & python3 --version 2>&1 | Select-Object -First 1 ; `
+    $exitCode = if ($null -eq $LASTEXITCODE) { if ($?) { 0 } else { 1 } } else { [int]$LASTEXITCODE } ; `
+    if ($exitCode -ne 0) { Write-Host "❌ Python3 FAILED: exited $exitCode"; exit 1 } ; `
+    Write-Host "  $out" ; `
+    Write-Host '✅ Python3 verified'
+
 RUN Write-Host '=== VERIFY: R ===' ; `
     $cmd = Get-Command Rscript -ErrorAction SilentlyContinue ; `
     if (-not $cmd) { Write-Host "❌ R FAILED: command not found"; exit 1 } ; `