Installs pyenv-win, a couple versions of python, and sets the global version.

install-pyenv-win.ps1

<#
    .SYNOPSIS
    Installs pyenv-win

    .DESCRIPTION
    Installs pyenv-win to $HOME\.pyenv
    If pyenv-win is already installed, try to update to the latest version.

    .PARAMETER Uninstall
    Uninstall pyenv-win. Note that this uninstalls any Python versions that were installed with pyenv-win.

    .PARAMETER Versions
    (Optional) A list of Python versions to install after pyenv-win is set up. Example usage: `.\install-pyenv-win.ps1 -Versions 3.12.10, 3.13.11, 3.14.2`
    Or, if you don't want to specify versions at install time, you can run `pyenv install <version>` after installation to install any version you want.
    Example: `./install-pyenv-win.ps1 -Versions ""` to skip installing versions at install time.

    .PARAMETER GlobalVersion
    (Optional) Set the global Python version after installation. Example usage: `.\install-pyenv-win.ps1 -Versions 3.12.10, 3.13.11, 3.14.2 -GlobalVersion 3.14.2`
    If not specified, the global version will not be set and will default to the system Python until you set it with `pyenv global <version>`.

    .EXAMPLE
    PS> install-pyenv-win.ps1

    .LINK
    Original online version: https://pyenv-win.github.io/pyenv-win/

    .NOTES
    To install or update pyenv-win, run this script in PowerShell. If you want to specify Python versions to install at the same time, use the -Versions parameter. 
    Example: `.\install-pyenv-win.ps1 -Versions 3.12.10, 3.13.11, 3.14.2`

    To download this script, you can use the following command in PowerShell:
    `irm "https://gist.githubusercontent.com/stevewithington/024fc85709d6c5a9e82dffcb9dee17a2/raw/281589d755f3fb46658c4df52ba88b9fd3efa609/install-pyenv-win.ps1" -OutFile install-pyenv-win.ps1`

    To uninstall pyenv-win, run this script with the -Uninstall switch: `.\install-pyenv-win.ps1 -Uninstall`

    To run in memory without downloading the script, you can use the following command:
    `irm "https://gist.githubusercontent.com/stevewithington/024fc85709d6c5a9e82dffcb9dee17a2/raw/281589d755f3fb46658c4df52ba88b9fd3efa609/install-pyenv-win.ps1" | iex`

#>

param (
    [Switch] $Uninstall,
    [String[]] $Versions = @('3.12.10', '3.13.11', '3.14.2'),
    [String] $GlobalVersion = '3.14.2'
)

Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'

$PyEnvDir = Join-Path $env:USERPROFILE '.pyenv'
$PyEnvWinDir = Join-Path $PyEnvDir 'pyenv-win'
$BinPath = Join-Path $PyEnvWinDir 'bin'
$ShimsPath = Join-Path $PyEnvWinDir 'shims'
$VersionUrl = 'https://raw.githubusercontent.com/pyenv-win/pyenv-win/master/.version'
$ArchiveUrl = 'https://github.com/pyenv-win/pyenv-win/archive/master.zip'

function Remove-PyEnvPaths {
    $PathParts = [System.Environment]::GetEnvironmentVariable('PATH', 'User') -split ';'
    $Cleaned = $PathParts.Where{ $_ -notin @($BinPath, $ShimsPath) }
    [System.Environment]::SetEnvironmentVariable('PATH', ($Cleaned -join ';'), 'User')
}

function Remove-PyEnvVars {
    Remove-PyEnvPaths
    foreach ($Var in 'PYENV', 'PYENV_ROOT', 'PYENV_HOME') {
        [System.Environment]::SetEnvironmentVariable($Var, $null, 'User')
    }
}

function Get-CurrentVersion {
    $VersionFile = Join-Path $PyEnvDir '.version'
    if (Test-Path $VersionFile) { return (Get-Content $VersionFile -Raw).Trim() }
    return $null
}

function Get-LatestVersion {
    return (Invoke-RestMethod -Uri $VersionUrl -UseBasicParsing).Trim()
}

function Install-PyEnv {
    $DownloadPath = Join-Path $PyEnvDir 'pyenv-win.zip'
    try {
        New-Item -Path $PyEnvDir -ItemType Directory -Force | Out-Null
        Invoke-WebRequest -Uri $ArchiveUrl -OutFile $DownloadPath -UseBasicParsing
        Expand-Archive -Path $DownloadPath -DestinationPath $PyEnvDir -Force

        $ExtractedDir = Join-Path $PyEnvDir 'pyenv-win-master'
        Get-ChildItem -Path $ExtractedDir | Move-Item -Destination $PyEnvDir -Force
        Remove-Item $ExtractedDir, $DownloadPath -Recurse -Force
    }
    catch {
        Write-Error "Download/extraction failed: $_"
        return $false
    }

    # Set environment variables
    $PyEnvWinTrailing = "$PyEnvWinDir\"
    foreach ($Var in 'PYENV', 'PYENV_ROOT', 'PYENV_HOME') {
        [System.Environment]::SetEnvironmentVariable($Var, $PyEnvWinTrailing, 'User')
    }

    # Update PATH — remove old entries first, then prepend
    $PathParts = [System.Environment]::GetEnvironmentVariable('PATH', 'User') -split ';'
    $Cleaned = $PathParts.Where{ $_ -notin @($BinPath, $ShimsPath) }
    $NewPath = (@($BinPath, $ShimsPath) + $Cleaned) -join ';'
    [System.Environment]::SetEnvironmentVariable('PATH', $NewPath, 'User')
    return $true
}

Function Install-Versions {
    foreach ($Version in $Versions) {
        Write-Host "Installing Python $Version..." -ForegroundColor Cyan
        & pyenv install $Version
        if ($LASTEXITCODE -ne 0) {
            Write-Host "Failed to install Python $Version. Please check the error message above and try installing manually with `pyenv install $Version`." -ForegroundColor Red
        }
    }
}

Function Set-GlobalVersion {
    if ($GlobalVersion) {
        Write-Host "Setting global Python version to $GlobalVersion..." -ForegroundColor Cyan
        & pyenv global $GlobalVersion
        if ($LASTEXITCODE -ne 0) {
            Write-Host "Failed to set global Python version to $GlobalVersion. Please check the error message above and try setting it manually with `pyenv global $GlobalVersion`." -ForegroundColor Red
        } else {
            Write-Host "Global Python version set to $GlobalVersion." -ForegroundColor Green
            $PythonVersion = & python --version
            if ($LASTEXITCODE -ne 0) {
                Write-Host "Failed to verify Python version after setting global version. Please ensure your terminal is restarted and try running `python --version`." -ForegroundColor Red
            }
            else {
                Write-Host "Current Python version: $PythonVersion" -ForegroundColor Green
                $SystemExe = python -c "import sys; print(sys.executable)"
                Write-Host "Python executable path: $SystemExe" -ForegroundColor Green
            }
        }
    }
}

# --- Main logic ---

if ($Uninstall) {
    Write-Host 'Removing pyenv-win...' -ForegroundColor Yellow
    if (Test-Path $PyEnvDir) { Remove-Item -Path $PyEnvDir -Recurse -Force }
    Remove-PyEnvVars
    Write-Host 'pyenv-win successfully uninstalled.' -ForegroundColor Green
    exit 0
}

$BackupDir = Join-Path $env:TEMP 'pyenv-win-backup'
$FoldersToBackup = @('install_cache', 'versions', 'shims')
$CurrentVersion = Get-CurrentVersion

if ($CurrentVersion) {
    Write-Host "pyenv-win $CurrentVersion installed." -ForegroundColor Green
    $LatestVersion = Get-LatestVersion
    if ($CurrentVersion -eq $LatestVersion) {
        Write-Host 'No updates available.'
        exit 0
    }
    Write-Host "New version available: $LatestVersion. Updating..." -ForegroundColor Cyan

    # Backup existing data in one pass
    New-Item -Path $BackupDir -ItemType Directory -Force | Out-Null
    foreach ($Dir in $FoldersToBackup) {
        $Source = Join-Path $PyEnvWinDir $Dir
        if (Test-Path $Source) { Move-Item -Path $Source -Destination $BackupDir }
    }
    Remove-Item -Path $PyEnvDir -Recurse -Force
}

if (Install-PyEnv) {
    # Restore backups if they exist
    if (Test-Path $BackupDir) {
        Write-Host 'Restoring Python installations...' -ForegroundColor Cyan
        Get-ChildItem -Path $BackupDir | Move-Item -Destination $PyEnvWinDir -Force
        Remove-Item -Path $BackupDir -Recurse -Force
    }
    Write-Host 'pyenv-win is successfully installed!' -ForegroundColor Green
    Write-Host 'Running `pyenv --version` to verify installation...' -ForegroundColor Cyan

    $pyenvVersion = & pyenv --version
    if ($LASTEXITCODE -ne 0) {
        Write-Host 'pyenv command failed to execute. Please ensure your terminal is restarted and try again.' -ForegroundColor Red
        exit 1
    }
    else {
        Write-Host "$pyenvVersion" -ForegroundColor Green
        if ($Versions.Count -gt 0) {
            Install-Versions
            Set-GlobalVersion
        }
    }

    Write-Host 'Installation complete! Visit https://pyenv-win.github.io/pyenv-win/#usage for usage instructions.' -ForegroundColor Cyan
}
else {
    Write-Host 'pyenv-win was not installed successfully. If this issue persists, please open a ticket: https://github.com/pyenv-win/pyenv-win/issues.' -ForegroundColor Red
    exit 1
}