1<#
2.Synopsis
3Activate a Python virtual environment for the current PowerShell session.
4
5.Description
6Pushes the python executable for a virtual environment to the front of the
7$Env:PATH environment variable and sets the prompt to signify that you are
8in a Python virtual environment. Makes use of the command line switches as
9well as the `pyvenv.cfg` file values present in the virtual environment.
10
11.Parameter VenvDir
12Path to the directory that contains the virtual environment to activate. The
13default value for this is the parent of the directory that the Activate.ps1
14script is located within.
15
16.Parameter Prompt
17The prompt prefix to display when this virtual environment is activated. By
18default, this prompt is the name of the virtual environment folder (VenvDir)
19surrounded by parentheses and followed by a single space (ie. '(.venv) ').
20
21.Example
22Activate.ps1
23Activates the Python virtual environment that contains the Activate.ps1 script.
24
25.Example
26Activate.ps1 -Verbose
27Activates the Python virtual environment that contains the Activate.ps1 script,
28and shows extra information about the activation as it executes.
29
30.Example
31Activate.ps1 -VenvDir C:\Users\MyUser\Common\.venv
32Activates the Python virtual environment located in the specified location.
33
34.Example
35Activate.ps1 -Prompt "MyPython"
36Activates the Python virtual environment that contains the Activate.ps1 script,
37and prefixes the current prompt with the specified string (surrounded in
38parentheses) while the virtual environment is active.
39
40.Notes
41On Windows, it may be required to enable this Activate.ps1 script by setting the
42execution policy for the user. You can do this by issuing the following PowerShell
43command:
44
45PS C:\> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
46
47For more information on Execution Policies: 
48https://go.microsoft.com/fwlink/?LinkID=135170
49
50#>
51Param(
52    [Parameter(Mandatory = $false)]
53    [String]
54    $VenvDir,
55    [Parameter(Mandatory = $false)]
56    [String]
57    $Prompt
58)
59
60<# Function declarations --------------------------------------------------- #>
61
62<#
63.Synopsis
64Remove all shell session elements added by the Activate script, including the
65addition of the virtual environment's Python executable from the beginning of
66the PATH variable.
67
68.Parameter NonDestructive
69If present, do not remove this function from the global namespace for the
70session.
71
72#>
73function global:deactivate ([switch]$NonDestructive) {
74    # Revert to original values
75
76    # The prior prompt:
77    if (Test-Path -Path Function:_OLD_VIRTUAL_PROMPT) {
78        Copy-Item -Path Function:_OLD_VIRTUAL_PROMPT -Destination Function:prompt
79        Remove-Item -Path Function:_OLD_VIRTUAL_PROMPT
80    }
81
82    # The prior PYTHONHOME:
83    if (Test-Path -Path Env:_OLD_VIRTUAL_PYTHONHOME) {
84        Copy-Item -Path Env:_OLD_VIRTUAL_PYTHONHOME -Destination Env:PYTHONHOME
85        Remove-Item -Path Env:_OLD_VIRTUAL_PYTHONHOME
86    }
87
88    # The prior PATH:
89    if (Test-Path -Path Env:_OLD_VIRTUAL_PATH) {
90        Copy-Item -Path Env:_OLD_VIRTUAL_PATH -Destination Env:PATH
91        Remove-Item -Path Env:_OLD_VIRTUAL_PATH
92    }
93
94    # Just remove the VIRTUAL_ENV altogether:
95    if (Test-Path -Path Env:VIRTUAL_ENV) {
96        Remove-Item -Path env:VIRTUAL_ENV
97    }
98
99    # Just remove VIRTUAL_ENV_PROMPT altogether.
100    if (Test-Path -Path Env:VIRTUAL_ENV_PROMPT) {
101        Remove-Item -Path env:VIRTUAL_ENV_PROMPT
102    }
103
104    # Just remove the _PYTHON_VENV_PROMPT_PREFIX altogether:
105    if (Get-Variable -Name "_PYTHON_VENV_PROMPT_PREFIX" -ErrorAction SilentlyContinue) {
106        Remove-Variable -Name _PYTHON_VENV_PROMPT_PREFIX -Scope Global -Force
107    }
108
109    # Leave deactivate function in the global namespace if requested:
110    if (-not $NonDestructive) {
111        Remove-Item -Path function:deactivate
112    }
113}
114
115<#
116.Description
117Get-PyVenvConfig parses the values from the pyvenv.cfg file located in the
118given folder, and returns them in a map.
119
120For each line in the pyvenv.cfg file, if that line can be parsed into exactly
121two strings separated by `=` (with any amount of whitespace surrounding the =)
122then it is considered a `key = value` line. The left hand string is the key,
123the right hand is the value.
124
125If the value starts with a `'` or a `"` then the first and last character is
126stripped from the value before being captured.
127
128.Parameter ConfigDir
129Path to the directory that contains the `pyvenv.cfg` file.
130#>
131function Get-PyVenvConfig(
132    [String]
133    $ConfigDir
134) {
135    Write-Verbose "Given ConfigDir=$ConfigDir, obtain values in pyvenv.cfg"
136
137    # Ensure the file exists, and issue a warning if it doesn't (but still allow the function to continue).
138    $pyvenvConfigPath = Join-Path -Resolve -Path $ConfigDir -ChildPath 'pyvenv.cfg' -ErrorAction Continue
139
140    # An empty map will be returned if no config file is found.
141    $pyvenvConfig = @{ }
142
143    if ($pyvenvConfigPath) {
144
145        Write-Verbose "File exists, parse `key = value` lines"
146        $pyvenvConfigContent = Get-Content -Path $pyvenvConfigPath
147
148        $pyvenvConfigContent | ForEach-Object {
149            $keyval = $PSItem -split "\s*=\s*", 2
150            if ($keyval[0] -and $keyval[1]) {
151                $val = $keyval[1]
152
153                # Remove extraneous quotations around a string value.
154                if ("'""".Contains($val.Substring(0, 1))) {
155                    $val = $val.Substring(1, $val.Length - 2)
156                }
157
158                $pyvenvConfig[$keyval[0]] = $val
159                Write-Verbose "Adding Key: '$($keyval[0])'='$val'"
160            }
161        }
162    }
163    return $pyvenvConfig
164}
165
166
167<# Begin Activate script --------------------------------------------------- #>
168
169# Determine the containing directory of this script
170$VenvExecPath = Split-Path -Parent $MyInvocation.MyCommand.Definition
171$VenvExecDir = Get-Item -Path $VenvExecPath
172
173Write-Verbose "Activation script is located in path: '$VenvExecPath'"
174Write-Verbose "VenvExecDir Fullname: '$($VenvExecDir.FullName)"
175Write-Verbose "VenvExecDir Name: '$($VenvExecDir.Name)"
176
177# Set values required in priority: CmdLine, ConfigFile, Default
178# First, get the location of the virtual environment, it might not be
179# VenvExecDir if specified on the command line.
180if ($VenvDir) {
181    Write-Verbose "VenvDir given as parameter, using '$VenvDir' to determine values"
182}
183else {
184    Write-Verbose "VenvDir not given as a parameter, using parent directory name as VenvDir."
185    $VenvDir = $VenvExecDir.Parent.FullName.TrimEnd("\\/")
186    Write-Verbose "VenvDir=$VenvDir"
187}
188
189# Next, read the `pyvenv.cfg` file to determine any required value such
190# as `prompt`.
191$pyvenvCfg = Get-PyVenvConfig -ConfigDir $VenvDir
192
193# Next, set the prompt from the command line, or the config file, or
194# just use the name of the virtual environment folder.
195if ($Prompt) {
196    Write-Verbose "Prompt specified as argument, using '$Prompt'"
197}
198else {
199    Write-Verbose "Prompt not specified as argument to script, checking pyvenv.cfg value"
200    if ($pyvenvCfg -and $pyvenvCfg['prompt']) {
201        Write-Verbose "  Setting based on value in pyvenv.cfg='$($pyvenvCfg['prompt'])'"
202        $Prompt = $pyvenvCfg['prompt'];
203    }
204    else {
205        Write-Verbose "  Setting prompt based on parent's directory's name. (Is the directory name passed to venv module when creating the virtual environment)"
206        Write-Verbose "  Got leaf-name of $VenvDir='$(Split-Path -Path $venvDir -Leaf)'"
207        $Prompt = Split-Path -Path $venvDir -Leaf
208    }
209}
210
211Write-Verbose "Prompt = '$Prompt'"
212Write-Verbose "VenvDir='$VenvDir'"
213
214# Deactivate any currently active virtual environment, but leave the
215# deactivate function in place.
216deactivate -nondestructive
217
218# Now set the environment variable VIRTUAL_ENV, used by many tools to determine
219# that there is an activated venv.
220$env:VIRTUAL_ENV = $VenvDir
221
222if (-not $Env:VIRTUAL_ENV_DISABLE_PROMPT) {
223
224    Write-Verbose "Setting prompt to '$Prompt'"
225
226    # Set the prompt to include the env name
227    # Make sure _OLD_VIRTUAL_PROMPT is global
228    function global:_OLD_VIRTUAL_PROMPT { "" }
229    Copy-Item -Path function:prompt -Destination function:_OLD_VIRTUAL_PROMPT
230    New-Variable -Name _PYTHON_VENV_PROMPT_PREFIX -Description "Python virtual environment prompt prefix" -Scope Global -Option ReadOnly -Visibility Public -Value $Prompt
231
232    function global:prompt {
233        Write-Host -NoNewline -ForegroundColor Green "($_PYTHON_VENV_PROMPT_PREFIX) "
234        _OLD_VIRTUAL_PROMPT
235    }
236    $env:VIRTUAL_ENV_PROMPT = $Prompt
237}
238
239# Clear PYTHONHOME
240if (Test-Path -Path Env:PYTHONHOME) {
241    Copy-Item -Path Env:PYTHONHOME -Destination Env:_OLD_VIRTUAL_PYTHONHOME
242    Remove-Item -Path Env:PYTHONHOME
243}
244
245# Add the venv to the PATH
246Copy-Item -Path Env:PATH -Destination Env:_OLD_VIRTUAL_PATH
247$Env:PATH = "$VenvExecDir$([System.IO.Path]::PathSeparator)$Env:PATH"
248