Powershell script that directly executes python script

Question

Wrote this script after having some problems with clients on Win10 and consequent necessity to ship ultra-bloated .exe file of Python project over the Web to them. This is my first try to write Powershell scripts (mostly used Linux & Shell scripts before), thus I guess code is not optimal and/or bloated and/or missing some critical steps.

How can I improve it?

The script is intended for users who have limited understanding of the operating system and Python and might not be inclined to learn more. The goal is for the script to be user-friendly: the user simply double-clicks it, and it performs its function seamlessly.

param (
    [switch]$ScanSystem = $true,
    [string]$ScanDrives = "C:,D:",
    [switch]$AllowCancel = $false,
    [switch]$Help,
    [switch]$InstallPython = $true,
    [switch]$SetupEnvironment = $true,
    [switch]$RecreateEnvironment = $false,
    [switch]$RemoveEnvironment = $false,
    [switch]$InstallDependencies = $true,
    [string]$PythonVersion = "3.11.7",
    [switch]$UpdatePip = $true,
    [double]$RequiredSpaceInGB = 1.0,
    [string]$ScriptName = "main.py"
)

# Check for the /help parameter and display script information
if ($Help) {
    Write-Host "USAGE:" -ForegroundColor Yellow
    Write-Host "`t.\scriptName.ps1 [PARAMETERS]`n"

    Write-Host "PARAMETER DESCRIPTION:" -ForegroundColor Yellow
    Write-Host "`t-ScanSystem`n`t`tChecks for Python presence in the entire system. Default is $true."
    Write-Host "`t`tExample: -ScanSystem:$false to disable system scan.`n"

    Write-Host "`t-ScanDrives`n`t`tSpecifies which drives to scan. Default is 'C:,D:'."
    Write-Host "`t`tExample: -ScanDrives 'E:,F:' to scan drives E: and F:.`n"

    Write-Host "`t-AllowCancel`n`t`tAllows to cancel execution. Default is $false."
    Write-Host "`t`tExample: -AllowCancel:$true to allow installation cancellation.`n"

    Write-Host "`t-InstallPython`n`t`tInstalls Python if not found. Default is $true."
    Write-Host "`t`tExample: -InstallPython:$false to not install Python.`n"

    Write-Host "`t-SetupEnvironment`n`t`tCreates and activates a virtual environment. Default is $true."
    Write-Host "`t`tExample: -SetupEnvironment:$false to not create an environment.`n"

    Write-Host "`t-InstallDependencies`n`t`tInstalls libraries from requirements.txt. Default is $true."
    Write-Host "`t`tExample: -InstallDependencies:$false to not install dependencies.`n"

    Write-Host "`t-PythonVersion`n`t`tSpecifies the Python version to install. Default is '3.11.7'."
    Write-Host "`t`tExample: -PythonVersion '3.9.1' to install Python 3.9.1.`n"

    Write-Host "`t-UpdatePip`n`t`tUpdates pip to the latest version. Default is $true."
    Write-Host "`t`tExample: -UpdatePip:$false to not update pip.`n"

    Write-Host "`t-RequiredSpaceInGB`n`t`tRequired amount of free disk space in GB. Default is 1.0."
    Write-Host "`t`tExample: -RequiredSpaceInGB 2.5 for installation if at least 2.5 GB is available.`n"

    Write-Host "`t-RecreateEnvironment`n`t`tRecreates the virtual environment if it already exists. Default is $false."
    Write-Host "`t`tExample: -RecreateEnvironment:$true to recreate the environment.`n"

    Write-Host "`t-RemoveEnvironment`n`t`tRemoves the virtual environment if it exists. Default is $false."
    Write-Host "`t`tExample: -RemoveEnvironment:$true to remove the environment.`n"

    Write-Host "`t-ScriptName`n`t`tSpecifies the Python script to execute. Default is 'main.py'."
    Write-Host "`t`tExample: -ScriptName 'script.py' to execute 'script.py'.`n"

    Write-Host "EXAMPLES:" -ForegroundColor Yellow
    Write-Host "`t.\start.ps1 -ScanSystem:$false -InstallPython:$true -PythonVersion '3.8.10' -UpdatePip:$true -ScriptName 'other_script.py'" -ForegroundColor Green
    Write-Host "`t.\start.ps1 -AllowCancel:$true -SetupEnvironment:$false -ScriptName 'run_me.py'`n" -ForegroundColor Green
    Pause
    Exit
}

# Setting the character encoding to UTF-8
$OutputEncoding = [System.Text.Encoding]::UTF8
chcp 65001

# To run in Windows PS ISE: execute the command below in the shell
# Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

Write-Host "###########################################" -ForegroundColor Yellow
Write-Host "#                                         #" -ForegroundColor Yellow
Write-Host "#     Automatic Python Installation       #" -ForegroundColor Yellow
Write-Host "#                                         #" -ForegroundColor Yellow
Write-Host "###########################################" -ForegroundColor Yellow
Write-Host "#                                         #" -ForegroundColor Yellow
Write-Host "# 1. Downloading and Installing Python    #" -ForegroundColor Yellow
Write-Host "# 2. Creating a Virtual Environment       #" -ForegroundColor Yellow
Write-Host "# 3. Installing Necessary Libraries       #" -ForegroundColor Yellow
Write-Host "#                                         #" -ForegroundColor Yellow
Write-Host "###########################################" -ForegroundColor Yellow
Write-Host "`nSeveral gigabytes of free space may be required to continue the installation.`n" -ForegroundColor Red
Write-Host "Current script run parameters:" -ForegroundColor Yellow
Write-Host "---------------------------------" -ForegroundColor Yellow
Write-Host "Scan System: $ScanSystem" -ForegroundColor Yellow
Write-Host "Scan Drives: $ScanDrives" -ForegroundColor Yellow
Write-Host "Allow Cancel: $AllowCancel" -ForegroundColor Yellow
Write-Host "Install Python: $InstallPython" -ForegroundColor Yellow
Write-Host "Setup Environment: $SetupEnvironment" -ForegroundColor Yellow
Write-Host "Install Dependencies: $InstallDependencies" -ForegroundColor Yellow
Write-Host "Python Version: $PythonVersion" -ForegroundColor Yellow
Write-Host "Update Pip: $UpdatePip" -ForegroundColor Yellow
Write-Host "Required Space: $RequiredSpaceInGB GB" -ForegroundColor Yellow
Write-Host "Recreate Environment: $RecreateEnvironment" -ForegroundColor Yellow
Write-Host "Remove Environment: $RemoveEnvironment" -ForegroundColor Yellow
Write-Host "---------------------------------" -ForegroundColor Yellow

if ($AllowCancel) {
    Write-Host "Press any key to continue or X to cancel the installation." -ForegroundColor Yellow
    $userInput = Read-Host "Select action"

    if ($userInput -ieq "X") {
        Write-Host "Installation canceled by the user. You may close the window." -ForegroundColor Red
        Pause
        exit
    }
}

Write-Host "Checking for an internet connection.."
try {
    $response = Invoke-WebRequest -Uri "http://www.python.org" -UseBasicParsing -TimeoutSec 5
    Write-Host "Internet connection is available." -ForegroundColor Green
} catch {
    Write-Host "No internet connection. Check your connection." -ForegroundColor Red
    Pause
    exit
}

$scanChoice = $ScanSystem
$scanDrives = $ScanDrives.Split(",").Trim()

if ($scanChoice) {
    Write-Host "You have chosen to scan the system for python.exe." -ForegroundColor Yellow
    $pythonPaths = Get-ChildItem -Path $scanDrives -Recurse -ErrorAction SilentlyContinue |
        Where-Object { $_.Name -match 'python[0-9.-]*\.exe$' } |
        Select-Object -ExpandProperty DirectoryName
} else {
    Write-Host "Scanning the system path for python.exe." -ForegroundColor Yellow
    $pathDirs = $env:PATH -split ';'
    $pythonPaths = $pathDirs | Where-Object { Test-Path "$_\python.exe" } | ForEach-Object { $_ }
}

if ($InstallPython -and $pythonPaths.Count -eq 0) {
    Write-Host "Python not found in standard locations. Attempting to install Python..." -ForegroundColor Red

    # Checking available disk space
    $drive = Get-PSDrive -Name (Get-Location).Drive.Name
    if ($drive.Free -lt $RequiredSpaceInGB * 1GB) {
        Write-Host "Not enough disk space to continue the installation. At least $RequiredSpaceInGB GB is required." -ForegroundColor Red
        Pause
        exit
    }

    # Maybe use winget? But it requires previous installation..
    $pythonInstaller = "python-$PythonVersion.exe"
    $pythonUrl = "https://www.python.org/ftp/python/$PythonVersion/$pythonInstaller"
    Invoke-WebRequest -Uri $pythonUrl -OutFile $pythonInstaller
    Write-Host "Download completed." -ForegroundColor Green

    Write-Host "Installing Python..."
    Start-Process $pythonInstaller -ArgumentList '/quiet InstallAllUsers=1 PrependPath=1' -Wait -NoNewWindow
    Write-Host "Python version $PythonVersion successfully installed." -ForegroundColor Green
} elseif ($pythonPaths.Count -eq 1) {
    $pythonPath = $pythonPaths[0]
    Write-Host "Found Python at: $pythonPath"
} else {
    Write-Host "Multiple Python installations found:"
    $i = 1
    foreach ($path in $pythonPaths) {
        Write-Host "$i`: $path"
        $i++
    }

    $selectedPythonIndex = Read-Host "Enter the number of the desired Python installation"
    if ($selectedPythonIndex -and $selectedPythonIndex -match '^\d+$' -and $selectedPythonIndex -le $pythonPaths.Count) {
        $pythonPath = $pythonPaths[$selectedPythonIndex - 1]
        Write-Host "You have selected Python at: $pythonPath" -ForegroundColor Green
    } else {
        Write-Host "Invalid input. Please enter a number corresponding to one of the listed paths." -ForegroundColor Red
        Pause
        exit
    }
}

# Path where Python is expected to be after installation
$pythonExecutable = Join-Path -Path $pythonPath -ChildPath "python.exe"

# Checking for presence
try {
    $pythonVersionOutput = & "$pythonPath\python.exe" --version
    if ($pythonVersionOutput -like "Python $PythonVersion*") {
        Write-Host "Python version $PythonVersion successfully installed." -ForegroundColor Green
    } else {
        throw "Python version does not match the expected: $PythonVersion"
    }
} catch {
    Write-Host "Error checking Python installation: $_" -ForegroundColor Red
    Pause
    exit
}

# Virtual environment management
$venvPath = ".\venv"
if ($RemoveEnvironment -and (Test-Path $venvPath)) {
    Write-Host "Removing existing virtual environment at $venvPath..." -ForegroundColor Yellow
    Remove-Item -Path $venvPath -Recurse -Force
    Write-Host "Virtual environment removed." -ForegroundColor Green
}

if ($SetupEnvironment -or $RecreateEnvironment) {
    if (Test-Path $venvPath) {
        if ($RecreateEnvironment) {
            Write-Host "Recreating virtual environment at $venvPath..." -ForegroundColor Yellow
            Remove-Item -Path $venvPath -Recurse -Force
            Write-Host "Old virtual environment removed." -ForegroundColor Green

            Write-Host "Creating virtual environment at $venvPath..." -ForegroundColor Yellow
            & "$pythonPath\python.exe" -m venv $venvPath
            Write-Host "Virtual environment created." -ForegroundColor Green
        } else {
            Write-Host "Virtual environment already exists at $venvPath. Using existing one." -ForegroundColor Yellow
        }
    }
}

if (Test-Path $venvPath) {
    # Activating the virtual environment
    $activateScript = Join-Path -Path $venvPath -ChildPath "Scripts\Activate.ps1"
    if (Test-Path $activateScript) {
        Write-Host "Activating virtual environment..." -ForegroundColor Yellow
        . $activateScript
    } else {
        Write-Host "Activation script not found: $activateScript" -ForegroundColor Red
    }
}


# Updating pip
if ($SetupEnvironment) {
    & "$pythonPath\python.exe" -m pip install --upgrade pip
}

# Installing dependencies
if ($InstallDependencies) {
    Write-Host "Installing necessary libraries..."
    & "$pythonPath\python.exe" -m pip install -r requirements.txt
}

# Running the specified script
Write-Host "Launching script $ScriptName..."
& "$pythonExecutable" $ScriptName
if ($LASTEXITCODE -ne 0) {
    Write-Host "Error executing script $ScriptName" -ForegroundColor Red
} else {
    Write-Host "Installation and script execution for $ScriptName completed." -ForegroundColor Green
}


Pause

Answer 1

The two things that jumped out at me are the wall of calls to Write-Host that can be cleaned up using Here-Strings, and how you are implementing the -Help switch.

Here-Strings in PowerShell are just multi-line string literals. They begin with @" and end with "@. The opening block of text when running the script is a prime candidate for this:

Write-Host = @"
###########################################
#                                         #
#     Automatic Python Installation       #
#                                         #
###########################################
#                                         #
# 1. Downloading and Installing Python    #
# 2. Creating a Virtual Environment       #
# 3. Installing Necessary Libraries       #
#                                         #
###########################################

@" -ForegroundColor Yellow

Write-Host "Several gigabytes of free space may be required to continue the installation." -ForegroundColor Red

Write-Host @"

Current script run parameters:
---------------------------------
Scan System: $ScanSystem
Scan Drives: $ScanDrives
Allow Cancel: $AllowCancel
Install Python: $InstallPython
Setup Environment: $SetupEnvironment
Install Dependencies: $InstallDependencies
Python Version: $PythonVersion
Update Pip: $UpdatePip
Required Space: $RequiredSpaceInGB GB
Recreate Environment: $RecreateEnvironment
Remove Environment: $RemoveEnvironment
---------------------------------
@" -ForegroundColor Yellow

The -Help parameter is an interesting problem in PowerShell. The get-help commandlet is the idiomatic way to implement help text, in conjunction with writing comment-based help topics. From experience, I've found that nobody (except me) remembers this command exists, or they habitually pass -Help to the script, because every other command line utility supports some variation of this. You can still implement your own -Help param while also utilizing the get-help commandlet:

if ($Help)
{
    get-help $PSCommandPath -Full
    exit
}

The remainder of the script looks as straight forward as any other installation wrapper script. The only improvement I would suggest is to define local functions in lieu of a myriad Write-Host "..." -ForgroundColor XXXX calls, but this would only serve to clean things up.

function WriteError([string] $message)
{
    Write-Host $message -ForegroundColor Red
}

function WriteWarning([string] $message)
{
    Write-Host $message -ForegroundColor Yellow
}

function WriteSuccess([string] $message)
{
    Write-Host $message -ForegroundColor Green
}

This simplifies things like

Write-Host "Not enough disk space to continue the installation. At least $RequiredSpaceInGB GB is required." -ForegroundColor Red

to:

WriteError "Not enough disk space to continue the installation. At least $RequiredSpaceInGB GB is required."

Not a dramatic difference, but at least you can tell at the beginning of the line of code that you are writing an error, as opposed to reading to the end to see -ForegroundColor Red.

I suppose you could put the forground color first, but then you need to pass the message with a parameter name:

Write-Host -ForegroundColor Red -Object "Not enough disk space..."

Defining local functions allows you to give them meaningful names, which also makes the code easier to understand.