Unreal Engine 5 crashes on Python plugin preload

Development Pipeline & Plugins
, ,
1

I’ve just installed UE5 Preview 1, but every time I’m trying to launch it, it instantly gives me this crash log:

Assertion failed: DLLHandle != nullptr [File:D:\build\++UE5\Sync\Engine\Plugins\Experimental\PythonScriptPlugin\Source\PythonScriptPluginPreload\Private\PythonScriptPluginPreload.cpp] [Line: 68]


UnrealEditor_PythonScriptPluginPreload
UnrealEditor_PythonScriptPluginPreload
UnrealEditor_Core
UnrealEditor_Projects
UnrealEditor_Projects
UnrealEditor_Projects
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

Looks like the problem is in Python scripting plugin, but what’s the exact cause and how to solve it?

2 Likes
2

This might be related to your install of Python 3.9? Have you looked into the crashlog? If it says it can’t load Python 3.9 you might want to copy the python39.dll from your python folder into where UE5 has its python39.dll location. In case you are still on win7… then you need to find the python 3.9 for win7 github and get it from there.

1 Like
3

hi
i have this problem
my windows is 7
and python 3.9 installing in the win 8 or higer
What should be done now to install this program on Windows 7?
Or made Unreal Engine 5 work in Windows 7

its bad
please help me

4

Exact same problem, win 7 x64.
UE5 Early access worked fine,
With UE5 preview I can’t start the engine nor open my old projects.

5

Same problem,same Win 7 x64.

6

Same problem. Win 7x64.

7

This is the fix for the Python 3.9 Problem under Windows 7 tested with UE5.0 Preview 2:

  1. Download Python 3.9.9+ Installer from (e.g. python-3.9.9-win7-amd64-*.exe):
    https://github.com/NulAsh/cpython/releases
    (Credits to NulAsh, he created a whole Windows 7 Version of Python 3.9!)
  2. Install it and remember path (Customize Installation)
  3. Go to your Python install folder (e.g. C:\Program Files\Python39) where your python39.dll is.
  4. Copy and overwrite the python39.dll to *UE_5.0\Engine\Binaries\Win64*
  5. Copy and overwrite the python39.dll to *UE_5.0\Engine\Binaries\ThirdParty\Python3\Win64*
    Unreal Engine 5.0 Preview 2 shoud now start.

I hope Epic Games will take account to this for the final Release, because I know a lot developers who are testing and some even developing under Windows 7.

19 Likes
8

thank you, it worked.
props to NulAsh :two_hearts:

1 Like
9

Thanks, that did it here too.

10

This got UE5 to start for me, but I had to replace the entire ThirdParty/Python3 folder with the 3.9.9-amd64 install.

1 Like
11

Python method above isn’t working … I’m still getting the same error trying to open UE5 and it kept crashing.

1 Like
12

I still can’t get it working with the above suggestions. Can you please elaborate more on what you did? The ThirdParty folder has a ton of stuff in it. How did you replace it? From where? Thanks!

14

Can confirm this works, thanks!

1 Like
15

I tried the things suggested in this post, even copying the entire python folder but still, the UE5 crashed right after start.

Please, can anyone help how to fix it or release a fixed update soon?

Thank you very much!

16

I am doing the exact same thing as I posted above for 5.0.0 and it still fixes the launch problem on my Windows 7 machine.
There was no need to replace the whole Python3 directory inside Unreal engine for me as adeemlj mentioned.

If you still get a crash, make sure to provide some logs, screenshots, detailed info, … otherwise no one will be able to help you.

17

I tried it again today, the issue still exists. I have sent again the automated crash report with logs for the UE dev team.

I am trying to run it on 8-core i7 mobile CPU, 8 GB RAM with Win7 64-bit, DirectX 11 present.
The version of the replacement python was:
Python 3.9.9 (heads/3.9.9-win7:86f32f9d6a, Dec 6 2021, 09:53:04) [MSC v.1916 32 bit (Intel)] on win32

The visible error message in the crash window was this:

Assertion failed: DLLHandle != nullptr [File:D:\build++UE5\Sync\Engine\Plugins\Experimental\PythonScriptPlugin\Source\PythonScriptPluginPreload\Private\PythonScriptPluginPreload.cpp] [Line: 68]

UnrealEditor_PythonScriptPluginPreload
UnrealEditor_PythonScriptPluginPreload
UnrealEditor_Core
UnrealEditor_Projects
UnrealEditor_Projects
UnrealEditor_Projects
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

18

from what your python says it is for 32 bit. Try installing the 64bit instead.

19

I don’t see a 64bit version for Intel at that NulAsh github page. If I do not want to build it myself from the source, what options do I have for getting the 64bit version?

20

As described in my first post it is named something like amd64 and you can find it under releases.

1 Like
21

The ThirdParty folder has a Python folder in it, which looks to just be a regular python install. Sometimes this happens because the developer wants to make sure that a required python version is present on the system, without making it an explicit requirement.

I just took the zipped python distribution from above and extracted it into that location, replacing the entire structure (they match exactly). I also replaced the python39.dll in the other locations suggested above.

Hope that helps.

(This got UE5 to start, and I can create projects, but I have run into additional problems getting it to build that I haven’t resolved yet. I’m a hair’s breadth from just switching to linux permanently.)

Edit: Just replacing the DLLs wasn’t enough to fix it on my machine, but certainly that’s a less invasive way to start. I’m just sharing what worked for me!

1 Like