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Installing Thonny

Here are some of the most common problems installing Thonny on Windows computers.

Missing or Corrupted Installer

Description: Sometimes the Thonny installer file is not completely downloaded, becomes corrupted, or is flagged incorrectly by antivirus software.

Solution:

  • Re-download the installer directly from the official website: https://thonny.org
  • Make sure the file is not blocked by antivirus software or Windows Defender.
  • Right-click the installer, select “Properties,” and check for a message at the bottom saying “This file came from another computer…” and click “Unblock” if present.
  • Run the installer as an administrator.

Insufficient Permissions

Description: Thonny may fail to install or run properly if the user account lacks administrative privileges, especially when trying to write to system directories.

Solution:

  • Right-click the installer and select "Run as administrator."
  • If you're in a managed environment (e.g., school or work PC), contact your IT admin for permissions or install in your local user directory.

Thonny Not Launching After Installation

Description: After a successful installation, Thonny may not start due to misconfigured environments or missing dependencies.

Solution:

  • Try launching Thonny from the command line (cmd) with:

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"C:\Program Files (x86)\Thonny\thonny.exe"
* If it doesn't open, reinstall Thonny with the "Just for me" option instead of "All users". * Check your antivirus logs to see if it's blocking Thonny.


Python Not Found or Wrong Version

Description: Although Thonny includes its own Python interpreter, some installations can conflict with system-installed Python, especially if PATH is misconfigured.

Solution:

  • Use the bundled version of Thonny that includes Python (recommended).
  • Avoid modifying the PATH manually unless you're managing multiple Python versions.
  • Check the Tools → Options → Interpreter setting in Thonny to verify which interpreter is being used.

Serial Port Not Found (for MicroPython/PyBoard)

Description: When trying to use Thonny with a microcontroller like Raspberry Pi Pico or ESP32, the serial port may not appear.

Solution:

  • Install the correct USB drivers (e.g., CH340 or CP210x).
  • Try a different USB cable (many are power-only).
  • Restart the computer after driver installation.
  • Use Device Manager to check if the device is recognized and assigned a COM port.

Thonny Crashes or Freezes

Description: Thonny can crash or become unresponsive due to plugin issues, corrupted user settings, or insufficient memory on older machines.

Solution:

  • Reset Thonny’s configuration: Run the following command in a terminal:

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thonny --reset
* Alternatively, delete or rename the Thonny configuration folder: C:\Users\<YourName>\AppData\Roaming\Thonny * Update Thonny to the latest version, or try installing a previous stable version.


Thonny Plugin Installation Fails

Description: When trying to install additional packages or plugins via Thonny’s Tools → Manage Packages, the installation may fail.

Solution:

  • Ensure you're using the bundled Thonny Python interpreter.
  • Use the “Simple” interface when prompted for installation options.
  • If needed, install the package manually in the command line using:
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C:\Users\<YourName>\AppData\Local\Programs\Thonny\python.exe -m pip install <package-name>

Windows Defender SmartScreen Blocking Thonny

Description: The SmartScreen filter may prevent Thonny from running by showing a warning message.

Solution:

  • Click "More info" and then "Run anyway."
  • Consider whitelisting Thonny in your security software if this becomes recurring.

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