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Overview

The Python Setup options control which Python interpreter is used to run your scripts. You can use the Windows Python Launcher (py.exe), a specific Python installation, or even a portable Python distribution.

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Configuration Options

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pythonversion
string
default:"3.11"
Specifies the Python version to use when pythondir is set to py or py.exe. This parameter is passed to the Windows Python Launcher to select the appropriate installed version.Valid values:
  • 3.11 - Python 3.11.x
  • 3.10 - Python 3.10.x
  • 3.9 - Python 3.9.x
  • 3 - Latest Python 3.x version
  • 2 - Latest Python 2.x version (if installed)
This setting is ignored if pythondir points to a specific Python executable.
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pythondir
string
default:"py"
Defines the Python executable or launcher command to use. This is the most flexible configuration option for Python setup.Valid values:
  • py - Use Windows Python Launcher (recommended)
  • py.exe - Explicit Windows Python Launcher path
  • python - Use system PATH Python
  • python.exe - Explicit system Python
  • C:\Python311\python.exe - Absolute path to specific installation
  • %cd%\python\python.exe - Relative path to portable Python
Using py is recommended as it works with the pythonversion setting to automatically select the correct Python version.

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Usage Examples

The Windows Python Launcher (py.exe) is the recommended approach as it allows easy version switching: 
::Use Python 3.11 via Windows Python Launcher
set pythonversion=3.11
set pythondir=py
This configuration will execute Python scripts using the command: 
py -3.11 script.py

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Using a Specific Python Installation

If you need to use a specific Python installation, provide the full path: 
::Ignore pythonversion and use specific installation
set pythonversion=3.11
set pythondir=C:\Python311\python.exe
When pythondir points to a specific python.exe, the pythonversion setting is ignored.

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Using Portable Python

For portable Python distributions that live within your project directory: 
::Use portable Python in project subdirectory
set pythonversion=3.11
set pythondir=%cd%\portable-python\python.exe
The %cd% variable represents the current directory where the batch file is located.
Portable Python is useful for:
  • Projects that need to be self-contained
  • Environments without admin rights
  • Ensuring consistent Python versions across machines

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Using System PATH Python

If you have Python in your system PATH: 
::Use whatever python.exe is in PATH
set pythonversion=3.11
set pythondir=python

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Version Selection Details

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How pythonversion Works

When using py or py.exe as the pythondir, the launcher uses the Windows Python Launcher’s version selection: 
py -3.11    # Runs Python 3.11.x (latest patch version)
py -3.10    # Runs Python 3.10.x
py -3       # Runs latest Python 3.x

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Checking Installed Versions

To see which Python versions are available on your system: 
py --list
Output example: 
 -3.11-64 *
 -3.10-64
 -3.9-64
The asterisk indicates the default version.

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Common Configurations

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Latest Python 3

set pythonversion=3
set pythondir=py
Uses the latest Python 3.x version installed on the system.

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Specific Minor Version

set pythonversion=3.11
set pythondir=py
Uses the latest Python 3.11.x patch version.

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Development Environment

::Use bleeding-edge Python for testing
set pythonversion=3.13
set pythondir=py

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Legacy Project

::Maintain compatibility with older Python
set pythonversion=3.8
set pythondir=py

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Troubleshooting

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Python Not Found

If you see “No python version was found!”, check:
  1. Is Python installed? Run py --version in a command prompt
  2. Is the version available? Run py --list to see installed versions
  3. Is the path correct? Verify absolute paths exist
  4. Is py.exe available? The Windows Python Launcher comes with Python 3.3+

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Wrong Python Version Running

If the wrong version executes:
  1. Verify pythondir is set to py or py.exe
  2. Check that pythonversion matches an installed version
  3. Run py --list to confirm the version is available
  4. Try using the full version number (e.g., 3.11.5 instead of 3.11)

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Portable Python Issues

If portable Python fails to run:
  1. Verify the path is correct (check for typos)
  2. Ensure python.exe exists at the specified location
  3. Use absolute paths if relative paths aren’t working
  4. Check that the portable Python distribution is complete
The alertifpynotinstalled configuration option (see Window Options) controls whether users are directed to download Python if it’s not found.

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Best Practices

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Use Windows Python Launcher

When possible, use py with pythonversion rather than direct paths. This provides:
  • Easy version switching
  • Better compatibility across machines
  • Automatic selection of latest patch versions

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Document Version Requirements

Add comments explaining why specific versions are required: 
::TensorFlow 2.12 requires Python 3.8-3.11
set pythonversion=3.11
set pythondir=py

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Test Multiple Versions

If your project should support multiple Python versions, create separate launcher files:
  • PythonLauncher-3.11.bat
  • PythonLauncher-3.10.bat
  • PythonLauncher-3.9.bat

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Team Consistency

For team projects, commit the launcher configuration to version control and document the required Python version in your README.