diff -rupN --no-dereference gmsh-4.12.1-source/CMakeLists.txt gmsh-4.12.1-source-new/CMakeLists.txt
--- gmsh-4.12.1-source/CMakeLists.txt	2024-01-11 11:22:45.000000000 +0100
+++ gmsh-4.12.1-source-new/CMakeLists.txt	2024-01-14 16:15:45.343990228 +0100
@@ -1945,6 +1945,8 @@ else()
   set(GMSH_INC ${CMAKE_INSTALL_INCLUDEDIR})
 endif()
 
+execute_process ( COMMAND python3 -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())" OUTPUT_VARIABLE PYTHON3_SITE_PACKAGES OUTPUT_STRIP_TRAILING_WHITESPACE)
+
 # mark targets as optional so we can install them separately if needed
 # (e.g. "make lib" or "make shared" followed by "make install/fast")
 install(TARGETS gmsh DESTINATION ${GMSH_BIN} OPTIONAL)
@@ -1956,14 +1958,14 @@ if(ENABLE_BUILD_SHARED OR ENABLE_BUILD_D
 endif()
 
 if(ENABLE_ONELAB AND EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/contrib/onelab)
-  install(FILES ${ONELAB_PY} DESTINATION ${GMSH_BIN})
+  install(FILES ${ONELAB_PY} DESTINATION ${PYTHON3_SITE_PACKAGES})
 endif()
 if(ENABLE_BUILD_LIB OR ENABLE_BUILD_SHARED OR ENABLE_BUILD_DYNAMIC)
   install(FILES ${GMSH_API} DESTINATION ${GMSH_INC})
-  install(FILES ${GMSH_PY} DESTINATION ${GMSH_LIB})
+  install(FILES ${GMSH_PY} DESTINATION ${PYTHON3_SITE_PACKAGES})
   install(FILES ${GMSH_JL} DESTINATION ${GMSH_LIB})
   install(FILES ${CMAKE_CURRENT_BINARY_DIR}/METADATA DESTINATION
-                ${GMSH_LIB}/gmsh-${GMSH_PYTHON_VERSION}.dist-info)
+                ${PYTHON3_SITE_PACKAGES}/gmsh-${GMSH_PYTHON_VERSION}.dist-info)
   if(ENABLE_PRIVATE_API)
     install(FILES ${GMSH_PRIVATE_API} DESTINATION ${GMSH_INC}/gmsh)
     if(HAVE_CONTRIB_EIGEN) # the private API depends on Eigen
diff -rupN --no-dereference gmsh-4.12.1-source/src/common/GmshMessage.cpp gmsh-4.12.1-source-new/src/common/GmshMessage.cpp
--- gmsh-4.12.1-source/src/common/GmshMessage.cpp	2024-01-11 11:22:47.000000000 +0100
+++ gmsh-4.12.1-source-new/src/common/GmshMessage.cpp	2024-01-14 16:15:45.343990228 +0100
@@ -173,14 +173,6 @@ void Msg::Initialize(int argc, char **ar
   if(CTX::instance()->exeFileName.empty() && _commandLineArgs.size())
     CTX::instance()->exeFileName = _commandLineArgs[0];
 
-  if(_env) {
-    // add the directory where the binary is installed to the path where Python
-    // looks for modules, and to the path for executables (this allows us to
-    // find the onelab.py module or subclients automatically)
-    addGmshPathToEnvironmentVar("PYTHONPATH");
-    addGmshPathToEnvironmentVar("PATH");
-  }
-
   if(_locale) {
     // make sure to use the "C" locale; in particular this ensures that we will
     // use a dot for for the decimal separator when writing ASCII mesh files