PythonSelect.psm1
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<#
.SYNOPSIS Makes the specified Python distribution the active one for the current session. .DESCRIPTION A Python distribution is considered "active" when its installation and script locations are both in the current PATH environment variable and are not shadowed by another distribution. When a Python distribution is enabled, the PATH is scrubbed of any references to any other Python distribution. Then the selected distribution's installation and script locations are appended to the PATH. The environment changes remain active only for the current session. Once a distribution has been enabled, references in the PATH to Python locations should NOT be added, removed, or modified. This may interfere with future attempts to enable different Python environments within the same session. Parameters can be given to select the distribution that should be enabled. These parameters behave exactly like those passed to Get-PythonDistribution. See the help for Get-PythonDistribution for more information. If no parameters are given, then this will attempt to enable the latest version of the official Python distribution found on the system. If no distributions are found matching the given parameters or multiple distributions are found, then this will fail. .PARAMETER Company Selects and activates a distribution whose company matches the given value. .PARAMETER Tag Selects and activates a distribution whose tag matches the given value. .PARAMETER Version Selects and activates a distribution whose version matches the given value. This can also be set to "latest", which causes only the most recent version of those distributions matching the other filter criteria to be activated. .PARAMETER Bitness Selects and activates a distribution whose bitness matches the given value. .PARAMETER Scope Selects and activates a distribution whose scope matches the given value. #> function Enable-Python { [CmdletBinding()] param( [Parameter()] [string] $Company, [Parameter()] [string] $Tag, [Parameter()] [string] $Version, [Parameter()] [ValidateSet( "32", "64" )] [string] $Bitness, [Parameter()] [ValidateSet( "System" , "CurrentUser" )] [string] $Scope ) $ErrorActionPreference = "Stop" # If no selection criteria is given, we'll try to select the latest version of the standard Python distribution. if( -not $Company -and -not $Tag -and -not $Version ) { Write-Host "No distribution information given. Searching for latest version of the standard Python distribution." $Company = "PythonCore" $Version = "latest" # If no bitness was selected, then we'll try to select the one whose bitness matches the current environment. if( -not $Bitness ) { $Bitness = if( [System.Environment]::Is64BitProcess ) { "64" } else { "32" } } # Unless the user is requesting a specific scope, then make sure we search the system scope. if( -not $Scope ) { $Scope = "System" } } $getArgs = @{} if( $Company ) { $getArgs.Company = $Company } if( $Tag ) { $getArgs.Tag = $Tag } if( $Version ) { $getArgs.Version = $Version } if( $Bitness ) { $getArgs.Bitness = $Bitness } if( $Scope ) { $getArgs.Scope = $Scope } $distributions = Get-PythonDistribution @getArgs if( $distributions.Count -eq 0 ) { Write-Host "No Python distributions found matching given distribution information." throw "Failed to enable Python distribution. No distributions found." } if( $distributions.Count -gt 1 ) { Write-Host "Multiple Python distributions found matching given distribution information:" $distributions | Format-Table -Property Company,Tag,Version,Bitness,Scope | Out-Host throw "Failed to enable Python distribution. Ambiguous selection." } # If this is the first invocation of this cmdlet, wipe any Python paths the user may have previously had set. if( -not $global:EnablePythonAlreadySet ) { Get-PythonDistribution | Clear-PythonInstallPath $global:EnablePythonAlreadySet = $true } $distribution = $distributions[0] Write-Host "Python distribution found in $($distribution.InstallPath). Updating PATH." if( $global:EnablePythonInstallPath ) { Clear-PythonInstallPath -InstallPath $global:EnablePythonInstallPath } $environmentPaths = $env:Path.Split( [System.IO.Path]::PathSeparator, [System.StringSplitOptions]::None ) $environmentPaths += @( $distribution.InstallPath, (Join-Path $distribution.InstallPath "Scripts") ) $env:Path = [string]::Join( [System.IO.Path]::PathSeparator, $environmentPaths ) $global:EnablePythonInstallPath = $distribution.InstallPath } <# .SYNOPSIS Gets information on all registered Python distributions installed on the current system. .DESCRIPTION According to PEP 514 (https://www.python.org/dev/peps/pep-0514/), Python distributions are to register themselves on Windows using well-defined registry locations. Distributions can either be installed in a system-wide location or in a user-specific location. Within a given scope, distributions are differentiated by a pair of values denoting what PEP 514 refers to as the distribution's company and the tag. Each distribution can also be 32- or 64-bit. These identifying pieces of information can be used to discover which Python distributions are available to the user on the current system. They can also be used to filter the list of available distributions, which is useful for eventually enabling a particular distribution within the current session. When no arguments are given, information on all registered Python distributions with a valid installation are returned. The values returned can then be passed to Enable-Python to enable a specific distribution. Passing additional arguments will filter the list of returned distributions based on the filtered properties. A filter on a distribution property will match a distribution if any of the following conditions are met: 1. The distribution's property matches exactly the filtered value. 2. The distribution's property is prefixed by the filtered value. 3. The distribution's property is "like" the filtered value (according to the rules of the -like operator). This means the filtered value can contain wildcard characters. All comparisons and checks are done in a case-insensitive manner. .PARAMETER Company Returns distributions whose company matches the given value. .PARAMETER Tag Returns distributions whose tag matches the given value. .PARAMETER Version Returns distributions whose version matches the given value. This can also be set to "latest", which causes only the most recent version of those distributions matching the other filter criteria to be returned. .PARAMETER Bitness Returns distributions whose bitness matches the given value. .PARAMETER Scope Returns distributions whose scope matches the given value. #> function Get-PythonDistribution { [CmdletBinding()] param( [Parameter()] [string] $Company, [Parameter()] [string] $Tag, [Parameter()] [string] $Version, [Parameter()] [ValidateSet( "32", "64" )] [string] $Bitness, [Parameter()] [ValidateSet( "System", "CurrentUser" )] [string] $Scope ) $ErrorActionPreference = "Stop" $distributions = @() $distributionSets = @( @{ RegKeyPrefix = "HKLM:\SOFTWARE\Python" Scope = "System" }, @{ RegKeyPrefix = "HKLM:\SOFTWARE\WOW6432Node\Python" Scope = "System" } @{ RegKeyPrefix = "HKCU:\Software\Python" Scope = "CurrentUser" } ) foreach( $distributionSet in $distributionSets ) { if( -not $Scope -or $distributionSet.Scope -eq $Scope ) { foreach( $companyKey in (Get-ChildItem -Path $distributionSet.RegKeyPrefix -ErrorAction Ignore) ) { if( -not $Company -or (Compare-DistributionSelector $companyKey.PSChildName $Company) ) { foreach( $tagKey in (Get-ChildItem -Path $companyKey.PSPath) ) { if( -not $Tag -or (Compare-DistributionSelector $tagKey.PSChildName $Tag) ) { $installPathKey = Get-Item -Path "$($tagKey.PSPath)\InstallPath" -ErrorAction Ignore if( $installPathKey ) { $installPath = Get-ItemPropertyValue -Path $installPathKey.PSPath -Name "(Default)" # If we can't get the distribution version or bitness, this is usually because there is # no Python interpreter installed at the given install path. This would typically happen # if a distribution doesn't properly clean out its registry keys whenever it is removed. $distributionVersion = Get-DistributionVersion -InstallPath $installPath if( -not $distributionVersion ) { Write-Warning ("Cannot determine distribution version. Skipping distribution " + "located at install path $installPath (Company=$($companyKey.PSChildName), " + "Tag=$($tagKey.PSChildName), Scope=$($distributionSet.Scope)).") continue } if( $Version -and $Version -ne "latest" -and -not (Compare-DistributionSelector $distributionVersion $Version) ) { continue } $distributionBitness = Get-DistributionBitness -InstallPath $installPath if( -not $distributionBitness ) { Write-Warning ("Cannot determine distribution bitness. Skipping distribution " + "located at install path $installPath (Company=$($companyKey.PSChildName), " + "Tag=$($tagKey.PSChildName), Scope=$($distributionSet.Scope)).") continue } if( $Bitness -and -not (Compare-DistributionSelector $distributionBitness $Bitness) ) { continue } $distributions += [PSCustomObject]@{ Company = $companyKey.PSChildName Tag = $tagKey.PSChildName Version = $distributionVersion Bitness = $distributionBitness Scope = $distributionSet.Scope InstallPath = $installPath } } } } } } } } if( $Version -eq "latest" ) { $latestVersion = $distributions | ` % { [System.Version]$_.Version } | ` Measure-Object -Maximum | ` Select-Object -ExpandProperty Maximum $distributions = $distributions | ? { $_.Version -eq $latestVersion } } $distributions } <# .SYNOPSIS Removes traces of the given installation location to a particular Python distribution from the user's PATH. .DESCRIPTION This searches for the given installation location as well as $InstallPath\Scripts in the user's PATH environment variable. If either are found, then they are removed. These changes do not persist beyond the current session in which they are made. .PARAMETER InstallPath Root directory of the Python distribution to search for in the user's PATH. #> function Clear-PythonInstallPath { [CmdletBinding()] param( [Parameter( Mandatory, ValueFromPipelineByPropertyName )] [string[]] $InstallPath ) begin { $environmentPaths = $env:Path.Split( [System.IO.Path]::PathSeparator, [System.StringSplitOptions]::None ) $normalizedEnvironmentPaths = $environmentPaths | % { if( $_ ) { Get-NormalizedPath -Path $_ } else { "" } } $pathsToRemove = @() } process { foreach( $path in $InstallPath ) { $pythonPath = Get-NormalizedPath -Path $path $scriptsPath = Get-NormalizedPath -Path (Join-Path $path "Scripts") for( $iEnvPath = 0; $iEnvPath -lt $environmentPaths.Count; $iEnvPath++ ) { if( $pythonPath -eq $normalizedEnvironmentPaths[$iEnvPath] -or $scriptsPath -eq $normalizedEnvironmentPaths[$iEnvPath] ) { $pathsToRemove += $environmentPaths[$iEnvPath] } } } } end { $environmentPaths = $environmentPaths | ? { $pathsToRemove -notcontains $_ } $env:Path = [string]::Join( [System.IO.Path]::PathSeparator, $environmentPaths ) } } <# .SYNOPSIS Checks to see if the reference selector matches the given difference selector. Read the description to see what constitutes a match. .DESCRIPTION All comparisons are done in a case-insensitive manner. The rules for matching are as follows: 1. If the reference and difference selectors are equal, then the result is true. This is an exact match. 2. If the difference selector is a prefix of the reference selector, then the result is true. This is a prefix match. 3. If the reference selector is "like" the difference selector (as determined by the -like operator), then the result is true. This is a wildcard match. 4. In all other cases, the result is false. .PARAMETER Reference The selector against which the difference selector is compared. .PARAMETER Difference The selector to compare against the reference selector. This may contain wildcard characters. .EXAMPLE Perform an exact match. Compare-DistributionSelector -Reference PythonCore -Difference PythonCore $true .EXAMPLE Perform a prefix match. Compare-DistributionSelector -Reference 3.6.3 -Difference 3.6 $true .EXAMPLE Perform a wildcard match. Compare-DistributionSelector -Reference Continuum -Difference "Cont*" $true #> function Compare-DistributionSelector { [CmdletBinding()] param( [Parameter( Mandatory )] [string] $Reference, [Parameter( Mandatory )] [string] $Difference ) # First check for exact match. This always trumps everything. if( $Reference -eq $Difference ) { return $true } # Now do a prefix match. This is likely the most common type of fuzzy match we'll expect. For example, someone may # say they want to enable version 3.6, which will match version 3.6.3. if( $Reference.StartsWith( $Difference, [System.StringComparison]::OrdinalIgnoreCase ) ) { return $true } # Lastly we support wildcard matching. if( $Reference -like $Difference ) { return $true } $false } <# .SYNOPSIS Gets whether the Python interpreter installed at the given install location is 32- or 64-bit. .PARAMETER InstallPath Root directory of the Python distribution to check. #> function Get-DistributionBitness { [CmdletBinding()] param( [Parameter( Mandatory )] [string] $InstallPath ) $python = Get-Python -InstallPath $InstallPath if( $python ) { & $python -c "import struct; print( 8 * struct.calcsize( 'P' ) )" } } <# .SYNOPSIS Gets the version of the Python interpreter installed at the given install location in major.minor.micro format. .PARAMETER InstallPath Root directory of the Python distribution to check. #> function Get-DistributionVersion { [CmdletBinding()] param( [Parameter( Mandatory )] [string] $InstallPath ) $python = Get-Python -InstallPath $InstallPath if( $python ) { # Older versions of Python don't have support for the tuple field names major, minor, and micro. Instead, we # access the version info fields by their respective indexes. & $python -c "import sys; print( '%d.%d.%d' % (sys.version_info[0], sys.version_info[1], sys.version_info[2]) )" } } <# .SYNOPSIS "Normalizes" a path by ensuring it has exactly one trailing slash. .DESCRIPTION This is used to make directory path comparisons easier in, e.g,. Clear-PythonInstallPath. .PARAMETER Path The path to normalize. #> function Get-NormalizedPath { [CmdletBinding()] param( [Parameter( Mandatory )] [string] $Path ) # This is kind of hacky, but it's a way to ensure all the PATH items we care about have a trailing slash for easier # install path comparison. Join-Path $Path "" } <# .SYNOPSIS Gets the Python executable installed at the given installation location. .PARAMETER InstallPath Root directory of the Python distribution to get the executable from. #> function Get-Python { [CmdletBinding()] param( [Parameter( Mandatory )] [string] $InstallPath ) Get-Command (Join-Path $InstallPath "python.exe") -ErrorAction Ignore } |