Python default features

Development Pipeline & Plugins Editor Scripting
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1

Can it be that UE4 ditched all the basic python features like time, logging, …?
When I try to import it I really get weird errors that they can’t be linked, see below.
I really need these standard functionalities, not because of the unreal extension, but to extend the editor with other features, that don’t interact with unreal in the first way.

LogPython: import time
LogPython: Error: Traceback (most recent call last):
LogPython: Error:   File "<string>", line 1, in <module>
LogPython: Error: ImportError: /opt/dev/unrealengine/4.22/Engine/Binaries/ThirdParty/Python/Linux/lib/python2.7/lib-dynload/time.so: undefined symbol: PyExc_ValueError

LogPython: import logging
LogPython: Error: Traceback (most recent call last):
LogPython: Error:   File "<string>", line 1, in <module>
LogPython: Error:   File "/opt/dev/unrealengine/4.22/Engine/Binaries/ThirdParty/Python/Linux/lib/python2.7/logging/__init__.py", line 26, in <module>
LogPython: Error:     import sys, os, time, cStringIO, traceback, warnings, weakref, collections
LogPython: Error: ImportError: /opt/dev/unrealengine/4.22/Engine/Binaries/ThirdParty/Python/Linux/lib/python2.7/lib-dynload/time.so: undefined symbol: PyExc_ValueError

Could it be possible to just change the python version inside of unreal to get these features working?

2

Okay,

so upgrading to UE4.23.0 fixes these python errors.
import time works fine now!

But, importing other modules (like PyQt) does not work, as I’m getting errors like this:
PyQt4/QtCore.so: undefined symbol: PyUnicodeUCS4_AsLatin1String

Does anyone know what’s that all about? Does UE4 use another Unicode length?

3

Okay, fixed it with rebuilding the python api with the flag --enable-unicode=ucs4 in build_python_linux.sh

4

Hi msearl0001, thank you for posting this. I’ve run into the same issue. I wonder if you wouldn’t mind explaining a bit further. I made that change to build_python_linux.sh and ran it, but then how do I get Unreal to use that Python? Who uses this Python-Linux.tar that it creates? Why is there a RunMe.bat in here? Any help would be much appreciated

5

Hi,

so I’ve changed the /configure part in build_linux_python.sh to the following to also enable SSL in the python build. You have to build the ssl package first.

MY_PREFIX=/.../openssl-1.0.2t/release/usr/local/ssl

./configure --enable-optimizations --enable-shared --enable-unicode=ucs4 \
LDFLAGS="-L$MY_PREFIX/lib -L$MY_PREFIX/lib64 -Wl,-rpath=$MY_PREFIX/lib" \
LD_LIBRARY_PATH="$MY_PREFIX/lib:$MY_PREFIX/lib64" \
CPPFLAGS="-I$MY_PREFIX/include -I$MY_PREFIX/ssl -fPIC" \

Then the probably easiest solution is to copy the lib and header files to the Engine/Source/ThirdParty/Python/Linux folder.

Another way is to go to the Python.Build.cs file and add this at line 27:

if (PythonSDK == null)
{
	var customBuildPath = Path.Combine(EngineDir, "Source/ThirdParty/Python/Build/Linux/usr/local");

	Console.WriteLine("Custom Python SDK path: " + customBuildPath);

	if (Target.Platform == UnrealTargetPlatform.Linux)
	{
		PythonSDK = DiscoverPythonSDK(customBuildPath);
	}
}

This should get you working. Maybe you also have to check if the DiscoverPythonSDK works correctly with your build Python SDK version.

Cheers