Fixing the ‘Couldn’t launch python exit code 9009’ Error

Encountering the cryptic “Couldn’t launch python, exit code 9009” error when trying to run Python scripts is frustrating. This error prevents Python from starting and indicates an issue with your Python installation or environment.

In this comprehensive guide, we will explore the various causes of this error and systematic approaches to troubleshoot and resolve it.

Overview of Exit Code 9009

The “Couldn’t launch python, exit code 9009” message occurs when the Python interpreter fails to start due to an error.

Key characteristics of this error:

  • Appears when trying to launch Python interactively or via scripts.
  • Prevents any Python code from running.
  • Displays exit code 9009 after the message.
  • Typically appears on Windows, less common on Linux/macOS.
  • Indicates an issue with Python’s runtime environment.

The technical cause is that Python.exe exits with a 9009 exit status, which Windows interprets as a launch failure.

Understanding potential sources of this error will assist troubleshooting efforts.

Troubleshooting Methodology

There are several possible causes of exit code 9009, so structured troubleshooting is required. Follow these systematic steps:

1. Check Python Installation

First, verify Python is properly installed and the interpreter executable functions normally.

  • Open a command prompt/terminal and run python --version.
  • If it displays Python’s version, then basic installation is OK.
  • If it shows “command not found” or a similar error, Python is not correctly set up.

Reinstalling Python may be required if it’s missing entirely or critical files got corrupted.

2. Test with Simple Scripts

Create a simple Python script like:

print("Hello World")

Try running it from the command prompt:


If this basic script also produces exit code 9009, it indicates a core Python issue. If it works, then the problem likely lies in your original script’s dependencies and environment.

3. Validate Environment Variables

On Windows, check that these environment variables are set correctly:

  • PATH – Contains path to Python’s install directory.
  • PYTHONPATH – Set to Python’s Lib and DLLs directories.

Errors in these variables prevent Python from working properly. They can get corrupted or deleted.

On Linux/macOS, the variables differ but verify Python install paths are in PATH.

4. Inspect Dependency Versions

If your script uses third-party packages and libraries, version mismatches may cause Python to crash on launch.

Check that:

  • Dependent packages are installed for the correct Python version (2.x vs 3.x).
  • Package versions are compatible with each other.
  • Virtual environments are activated when running the script.

Updating and aligning dependencies can fix conflicts and issues.

5. Disable Antivirus or Firewall Software

Overzealous antivirus or firewall tools may block Python from launching properly. As a test:

  • Add Python’s directories to antivirus exclusions.
  • Whitelist Python through Windows Firewall or other security software.
  • Temporarily disable security software entirely and retest.

If Python then works, tweaking security configurations is needed for compatibility.

6. Use Debugger to Pinpoint Issue

More advanced users can use a debugger for insights into where specifically Python is crashing:

  • Launch Python with a debugger like python -m pdb
  • Step through code line-by-line until error occurs.
  • Examine stack traces and variables at time of crash.

Debugger output can reveal the problematic function, module, or line of code.

7. Reinstall Python Interpreter

If no other issues are found, reinstalling Python itself may be required as a last resort:

  • On Windows, run the Python installer again and select Repair or Uninstall then Reinstall.
  • On Linux, fully remove old Python versions then install fresh packages.
  • After reinstalling, retry running Python scripts.

This should reset Python to a clean working state if environmental issues were present.

Following this rigorous troubleshooting approach should uncover the root cause so it can be corrected.

Fixing Common Causes of Exit Code 9009

Based on the troubleshooting steps above, here are specific solutions for the most common causes of the “Couldn’t launch python” error:

Corrupted Python Installation

If Python’s files and directories have become corrupted, a reinstallation is needed:

  • Download the latest Python installer for your OS.
  • Fully uninstall existing Python versions.
  • Run the installer, modifying paths if needed.
  • Test launching python and running scripts.

This will replace any missing or damaged Python installation files.

Incorrect Environment Variables

Verify the PATH and PYTHONPATH environment variables are set properly:

  • PATH should contain the Python install directory.
  • PYTHONPATH should contain Python’s Lib and DLLs folders.
  • Open the Environment Variables control panel on Windows to check.

Resetting these variables will ensure Python can be located on your system.

Virtual Environment Not Activated

If using virtual environments, you must activate them before launching scripts:

# Windows

# Linux/macOS 
source myenv/bin/activate

Then Python and dependencies in myenv will be on the PATH during execution.

Dependency Version Mismatch

Check installed package versions match:

pip freeze

The output shows all installed packages and versions. Look for conflicts like:

  • Packages installed for Python 2.x rather than 3.x.
  • Different packages requiting incompatible versions of a dependency.

Use pip install -U to align packages to the same versions across your environment.

Security Software Interference

Add Python’s install paths to whitelist/exclusion lists in antivirus, firewall and other security tools:

# Example directories to exclude on Windows

This prevents security tools from blocking Python processes and access to its files.

Additional Troubleshooting Tips

Beyond the common solutions above, here are some additional techniques for stubborn exit code 9009 errors:

  • Launch Python from the command prompt with verbose logging enabled using python -v. Check for any warning messages.
  • On Windows, run sfc /scannow and DISM to check for system file corruptions impacting Python.
  • Try launching the script with different versions of Python (2.x vs 3.x) if you have multiple installed.
  • Split the script into smaller parts and execute each incrementally to isolate failing portions.
  • Search Python’s bug tracker for similar issues reported by others.
  • As a last resort, backup and reformat/reimage the OS if corrupt system files are suspected.

Persistence in following the troubleshooting steps will eventually uncover the specific cause in most cases.

Automated Resolution on Windows

For Windows users, specialized tools exist which can automatically diagnose and fix issues with Python:

These tools can quickly validate Python’s installation state and environment. They may automatically resolve certain issues as well.

Preventing Exit Code 9009 Errors

Once you have fixed the immediate exit code 9009 error, here are some tips to avoid it recurring:

  • Keep Python and all packages updated to latest versions.
  • Use virtual environments to isolate projects and dependencies.
  • Run regular sfc /scannow and DISM scans to detect system file corruption.
  • Exclude Python directories from antivirus/security scanning if issues arise.
  • Cleanly uninstall old Python versions after migrating to new installs.
  • Frequently backup Python project directories and repositories.
  • Maintain a requirements.txt file for each project to freeze dependency versions.

Following Python best practices will minimize the chances of a corrupted runtime environment.


The cryptic “Couldn’t launch python, exit code 9009” error can be frustrating to troubleshoot and fix. Key takeaways:

  • Methodically validate the Python install, environment variables, dependencies and security tools.
  • Reinstalling Python and packages may be required if corrupt.
  • Automated Windows tools can diagnose issues.
  • Freezing dependency versions prevents mismatches.
  • Restore Python from backup if environment gets corrupted.

Carefully following the troubleshooting steps outlined will allow you to isolate the root cause and correct it. Your Python scripts will then be able to run normally again.


Here are some helpful resources on troubleshooting exit code 9009 errors:

Utilizing the troubleshooting methodology and solutions outlined here along with these additional resources should allow you to permanently resolve exit code 9009 errors when launching Python. Your scripts will run normally again on Windows and other operating systems.

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