$BASE_URL = "https://www.python.org/ftp/python/"

$GET_PIP_URL = "https://bootstrap.pypa.io/get-pip.py"

$GET_PIP_PATH = "C:\get-pip.py"

function DownloadPython ($python_version, $platform_suffix) {

$webclient = New-Object System.Net.WebClient

$filename = "python-" + $python_version + $platform_suffix + ".msi"

$url = $BASE_URL + $python_version + "/" + $filename

$basedir = $pwd.Path + "\"

$filepath = $basedir + $filename

if (Test-Path $filename) {

Write-Host "Reusing" $filepath

return $filepath

}

# Download and retry up to 5 times in case of network transient errors.

Write-Host "Downloading" $filename "from" $url

$retry_attempts = 3

for($i=0; $i -lt $retry_attempts; $i++){

try {

$webclient.DownloadFile($url, $filepath)

break

}

Catch [Exception]{

Start-Sleep 1

}

}

Write-Host "File saved at" $filepath

return $filepath

}

function InstallPython ($python_version, $architecture, $python_home) {

Write-Host "Installing Python" $python_version "for" $architecture "bit architecture to" $python_home

if (Test-Path $python_home) {

Write-Host $python_home "already exists, skipping."

return $false

}

if ($architecture -eq "32") {

$platform_suffix = ""

} else {

$platform_suffix = ".amd64"

}

$filepath = DownloadPython $python_version $platform_suffix

Write-Host "Installing" $filepath "to" $python_home

$args = "/qn /i $filepath TARGETDIR=$python_home"

Write-Host "msiexec.exe" $args

Start-Process -FilePath "msiexec.exe" -ArgumentList $args -Wait -Passthru

Write-Host "Python $python_version ($architecture) installation complete"

return $true

}

function InstallPip ($python_home) {

$pip_path = $python_home + "/Scripts/pip.exe"

$python_path = $python_home + "/python.exe"

if (-not(Test-Path $pip_path)) {

Write-Host "Installing pip..."

$webclient = New-Object System.Net.WebClient

$webclient.DownloadFile($GET_PIP_URL, $GET_PIP_PATH)

Write-Host "Executing:" $python_path $GET_PIP_PATH

Start-Process -FilePath "$python_path" -ArgumentList "$GET_PIP_PATH" -Wait -Passthru

} else {

Write-Host "pip already installed."

}

}

function InstallPackage ($python_home, $pkg) {

$pip_path = $python_home + "/Scripts/pip.exe"

& $pip_path install $pkg

}

function main () {

InstallPython $env:PYTHON_VERSION $env:PYTHON_ARCH $env:PYTHON

InstallPip $env:PYTHON

InstallPackage $env:PYTHON wheel

}

main