TIP: Opening Pythagoras files (.pyt) and restoring icons

Do .pyt, .dwg or .dxf files no longer open with a double-click, or is the Pythagoras icon missing? 
Or when opening a file, you may see the following message:

This file does not have an app associated with it for performing this action. Please install an app or, if one is already installed, create an association in the Default Apps Settings page.

Check the settings below.

Set Pythagoras as the default app for .pyt files

You can change which application Windows uses to open a particular file type:

1. Open the Start menu > Settings.

2. Go to Apps > Default apps.

3. Scroll down and select Choose defaults by file type.

4. Under Search for a file type, enter .pyt.

5. Click Choose a default.

6. Select Pythagoras from the list and click Set default.

Repeat this separately for .dwg and .dxf if you also want to open these files with Pythagoras by default.

Pythagoras is set as the default app, but the file does not open

After an older Pythagoras version has been uninstalled, Windows may still refer to its installation folder. In that case, check the application path in the Windows registry.

Open Registry Editor

1. Open the Windows Start menu.

2. Search for regedit.

3. Open Registry Editor. Confirm if prompted.

Check and update the application path

1. Copy the registry path below and paste it into the address bar, directly below the menu. Press Enter.

   Computer\HKEY_CLASSES_ROOT\Applications\pythagoras.exe\shell\open\command

2. On the right, check the Data column to see whether the path points to your current Pythagoras installation.

3. Does the path point to an old or deleted installation folder? Double-click (Default).

4. In the Edit String window, update the application path in Value data.

   For a standard Pythagoras 2025 installation, the complete value looks like this:

   "C:\Program Files\Pythagoras 2025\pythagoras.exe" "%1"

   Use the actual installation path on your computer. Keep the double quotation marks and "%1" at the end.

5. Click OK and close Registry Editor.

6. Double-click a .pyt file to check whether it opens.