Weird behaviour
Hello guys, I am facing weird bug while using CPython. When I use the below code, I am getting IronPython output.
#
#! python3
print("Hello from CPython")
import sys
print(sys.version)
Output -
Hello from CPython
2.7.12 (2.7.12.1000)
[.NETStandard,Version=v2.0 on .NET 8.0.27 (64-bit)]
But when I use the below code, I am getting error.
#! python3
print("Hello from CPython")
import sys
print(sys.version)
Can someone share the explaination ?
Jean-Marc
(Jean-Marc Couffin)
May 23, 2026, 6:05pm
2
Can you check the output of ‘pyrevit env’ command line?
@Jean-Marc Output from pyrevit env -
==> Registered Clones (full git repos)
==> Registered Clones (deployed from archive/image)
master | Branch: "master" | Version: "6.4.0.26100+0515" | Path: "C:\Users\ACER\AppData\Roaming\pyRevit-Master"
==> Attachments
master | Product: "2027" | Engine: DEFAULT (2712) | Path: "C:\Users\ACER\AppData\Roaming\pyRevit-Master"
master | Product: "2026 First Customer Ship" | Engine: DEFAULT (2712) | Path: "C:\Users\ACER\AppData\Roaming\pyRevit-Master"
master | Product: "2025 First Customer Ship" | Engine: DEFAULT (2712) | Path: "C:\Users\ACER\AppData\Roaming\pyRevit-Master"
master | Product: "2024.3.4" | Engine: DEFAULT (2712) | Path: "C:\Users\ACER\AppData\Roaming\pyRevit-Master"
==> Installed Extensions
guRoo | Type: Unknown | Repo: "https://github.com/aussieBIMguru/guRoo.git" | Installed: "D:\Software files\Revit\pyRevit plugins\guRoo.extension"
pyChai_dev | Type: UIExtension | Repo: "" | Installed: "D:\Code Development\Projects\BIM\Revit\pyChai\extensions\pyChai_dev.extension"
==> Default Extension Search Path
C:\Users\ACER\AppData\Roaming\pyRevit\Extensions
==> Extension Search Paths
D:\Code Development\Projects\BIM\Revit\pyChai\extensions
D:\Software files\Revit\pyRevit plugins
==> Extension Sources - Default
https://github.com/pyrevitlabs/pyRevit/raw/master/extensions/extensions.json
==> Extension Sources - Additional
==> Installed Revits
2027 | Version: 27.0.4.412 | Build: 20260228_1515(x64) | Language: 1033 | Path: "C:\Program Files\Autodesk\Revit 2027\"
2026 First Customer Ship | Version: 26.0.4.409 | Build: 20250227_1515(x64) | Language: 1033 | Path: "C:\Program Files\Autodesk\Revit 2026\"
2025 First Customer Ship | Version: 25.0.2.419 | Build: 20240307_1300(x64) | Language: 1033 | Path: "C:\Software installed\Autodesk\Revit 2025\"
2024.3.4 | Version: 24.3.40.26 | Build: 20250918_1515(x64) | Language: 1033 | Path: "C:\Software installed\Autodesk\Revit 2024\"
==> Running Revit Instances
Error: Object reference not set to an instance of an object.
Run with "--debug" option to see debug messages
For now, I have to use python subprocess as a workaround.
Jean-Marc
(Jean-Marc Couffin)
May 26, 2026, 10:13am
5
it seems the #! is ignored
please create an issue in the repo
porrt23
(Porter Wilde)
May 29, 2026, 7:41pm
6
opened 02:20PM - 10 Apr 26 UTC
closed 12:03PM - 11 Apr 26 UTC
Bug
### ✈ Pre-Flight checks
- [x] I **don't have SentinelOne** antivirus installed … (see above for the solution)
- [x] I have **searched in the issues** (open and closed) but couldn't find a similar issue
- [x] I have **searched in the [pyRevit Forum](https://discourse.pyrevitlabs.io)** for similar issues
- [x] I already **followed the [installation troubleshooting guide](https://pyrevitlabs.notion.site/Installation-issues-f6495adb56254e9e8021f8a68e3b2ab7) thoroughly**
- [x] I am using the **latest pyRevit Version**
### 🐞 Describe the bug
when runing a cpython script im getting an error prompt
### ⌨ Error/Debug Message
```shell
when runing a CPython script, for ex. Test CPython command (from pyRevitDev): "Revit could not complete the external command..Revit encountered a The type initializer for wDeligatesw threw an exception".
when runing test CPython engine. the output window shows:
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\pyRevitDev.tab\Debug.panel\Engine Tests.pulldown\Test CPython Engine.pushbutton
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\lib
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\pyRevitDev.tab\Debug.panel\Engine Tests.pulldown\Test IronPython Search Paths.pushbutton\lib
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\pyRevitDev.tab\Debug.panel\Engine Tests.pulldown\Test IronPython Search Paths.pushbutton\bin
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\pyRevitDev.tab\Debug.panel\Engine Tests.pulldown\Test CPython Engine.pushbutton
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\pyrevitlib
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\site-packages
C:\Users\betsalel\AppData\Roaming\pyRevit-Master\bin\netcore
IronPython Traceback:
Traceback (most recent call last):
File "C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\pyRevitDev.tab\Debug.panel\Engine Tests.pulldown\Test CPython Engine.pushbutton\script.py", line 28, in <module>
File "C:\Users\betsalel\AppData\Roaming\pyRevit-Master\extensions\pyRevitDevTools.extension\pyRevitDev.tab\Debug.panel\Engine Tests.pulldown\Test CPython Engine.pushbutton\script.py", line 28, in <module>
SystemError: The type initializer for 'Delegates' threw an exception.
Script Executor Traceback:
System.TypeInitializationException: The type initializer for 'Delegates' threw an exception.
---> Python.Runtime.BadPythonDllException: Runtime.PythonDLL was not set or does not point to a supported Python runtime DLL. See https://github.com/pythonnet/pythonnet#embedding-python-in-net
---> System.MissingMethodException: Failed to load symbol Py_IncRef.
---> System.ComponentModel.Win32Exception (127): The specified procedure could not be found.
--- End of inner exception stack trace ---
at Python.Runtime.Platform.WindowsLoader.GetFunction(IntPtr hModule, String procedureName)
at Python.Runtime.Runtime.Delegates.GetFunctionByName(String functionName, IntPtr libraryHandle)
--- End of inner exception stack trace ---
at Python.Runtime.Runtime.TryUsingDll[T](Func`1 op)
at Python.Runtime.Runtime.Initialize(Boolean initSigs)
at Python.Runtime.PythonEngine.Initialize(IEnumerable`1 args, Boolean setSysArgv, Boolean initSigs)
at Python.Runtime.PythonEngine.Initialize(Boolean setSysArgv, Boolean initSigs)
at Python.Runtime.PythonEngine.Initialize()
at Microsoft.Scripting.Interpreter.ActionCallInstruction.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.LightLambda.Run3[T0,T1,T2,TRet](T0 arg0, T1 arg1, T2 arg2)
at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
at Microsoft.Scripting.Interpreter.DynamicInstruction`3.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.LightLambda.Run2[T0,T1,TRet](T0 arg0, T1 arg1)
at IronPython.Compiler.PythonScriptCode.RunWorker(CodeContext ctx)
at IronPython.Compiler.PythonScriptCode.Run(Scope scope)
at IronPython.Compiler.RuntimeScriptCode.InvokeTarget(Scope scope)
at Microsoft.Scripting.Hosting.CompiledCode.Execute(ScriptScope scope)
at PyRevitLabs.PyRevit.Runtime.IronPythonEngine.Execute(ScriptRuntime& runtime)
--- End of inner exception stack trace ---
at Python.Runtime.Runtime.Delegates.get_PyErr_Clear()
at Python.Runtime.Runtime.PyErr_Clear()
at Python.Runtime.Exceptions.Clear()
at Python.Runtime.PythonEngine.Initialize(IEnumerable`1 args, Boolean setSysArgv, Boolean initSigs)
at Python.Runtime.PythonEngine.Initialize(Boolean setSysArgv, Boolean initSigs)
at Python.Runtime.PythonEngine.Initialize()
at Microsoft.Scripting.Interpreter.ActionCallInstruction.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.LightLambda.Run3[T0,T1,T2,TRet](T0 arg0, T1 arg1, T2 arg2)
at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
at Microsoft.Scripting.Interpreter.DynamicInstruction`3.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.LightLambda.Run2[T0,T1,TRet](T0 arg0, T1 arg1)
at IronPython.Compiler.PythonScriptCode.RunWorker(CodeContext ctx)
at IronPython.Compiler.PythonScriptCode.Run(Scope scope)
at IronPython.Compiler.RuntimeScriptCode.InvokeTarget(Scope scope)
at Microsoft.Scripting.Hosting.CompiledCode.Execute(ScriptScope scope)
at PyRevitLabs.PyRevit.Runtime.IronPythonEngine.Execute(ScriptRuntime& runtime)
```
### ♻️ To Reproduce
Run "Test CPython command" or "Test CPython engine" form the Debug panel in pyRevitDev tab.
### ⏲️ Expected behavior
_No response_
### 🖥️ Hardware and Software Setup (please complete the following information)
```shell
==> Registered Clones (full git repos)
==> Registered Clones (deployed from archive/image)
master | Branch: "master" | Version: "6.4.0.26100+0515" | Path: "C:\Users\betsalel\AppData\Roaming\pyRevit-Master"
==> Attachments
master | Product: "2026 First Customer Ship" | Engine: DEFAULT (2712) | Path: "C:\Users\betsalel\AppData\Roaming\pyRevit-Master"
==> Installed Extension
==> Default Extension Search Path
C:\Users\betsalel\AppData\Roaming\pyRevit\Extensions
==> Extension Search Paths
S:\BIM Utilities\pyRevit
==> Extension Sources - Default
https://github.com/pyrevitlabs/pyRevit/raw/master/extensions/extensions.json
==> Extension Sources - Additional
==> Installed Revits
2026 First Customer Ship | Version: 26.0.4.409 | Build: 20250227_1515(x64) | Language: 1033 | Path: "C:\Program Files\Autodesk\Revit 2026\"
==> Running Revit Instances
PID: 26216 | 2026.4 | Version: 26.4.0.32 | Build: 20251103_1515(x64) | Language: 0 | Path: "C:\Program Files\Autodesk\Revit 2026"
==> User Environment
Microsoft Windows 10 [Version 10.0.26200]
Executing User: FEIGIN\Betsalel
Active User:
Admin Access: No
%APPDATA%: "C:\Users\betsalel\AppData\Roaming"
Latest Installed .Net Framework: 10.0.2
No .Net Target Packs are installed.
No .Net-Core Target Packs are installed.
Active CPython Engine Version: 3123
pyRevit CLI v6.4.0.26100+0515.06e6e8108e8aaccfbb7080163a437e19236a8533
```
### Additional context
_No response_
A little late to this but have you tried the WIP build from this issue?
I guess this might be the issue.
One question though, do I have to uninstall existing stable version and install this WIP build? Or can I install alongside the stable version?
pyrevti
(pyrevti)
June 11, 2026, 5:43am
8
easiest would be to use the clone feature, if you’re comfortable with CLI
pyrevit clone dev --dest=“C:\pyRevit\dev” --branch=develop
and then attach the new clone via
pyrevit attach dev DEFAULT --installed
if a new WIP drops, you can then just
pyrevit clones update dev
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Oh nice! Will try this by upcoming weekend.