COMP: Initiate updating to find_package(Python3)

Now that cmake FindPython3 can be universally
used, prefer to only use that set of variable
names for identifying the python executables.

Intial procesing with manual cleanup by a mofified version
of the script used for ITK:

ITK/Utilities/Maintenance/FindPython3_ModernizeCMake.sh

This maintenance script can be used to assist with moving from
the deprecated find_package(PythonInterp) and find_package(PythonLib)
to the preferred find_package(Python3) variable names.

------------------------------
NOTE: This script is intended to make it easier
       to identify old find_package(PythonInterp
       uses, but it can not be blindly used.
       each change must be carefully reviewed.

```bash
\#!/bin/bash

COMMIT_INFO="COMP: Script to initiate updating to find_package(Python3)

Now that cmake FindPython3 can be universally
used, prefer to only use that set of variable
names for identifying the python executables.

Intial procesing with manual cleanup by:

ITK/Utilities/Maintenance/FindPython3_ModernizeCMake.sh

This maintenance script can be used to assist with moving from
the deprecated find_package(PythonInterp) and find_package(PythonLib)
to the preferred find_package(Python3) variable names.

------------------------------
NOTE: This script is intended to make it easier
       to identify old find_package(PythonInterp
       uses, but it can not be blindly used.
       each change must be carefully reviewed.
"

\# Utility functions
usage() {
cat << EOF
Usage: $0
$COMMIT_INFO
EOF
}

die() {
  echo "$@" 1>&2; exit 1
}

while test $# -gt 0;
do
  opt="$1";
  case "$opt" in
    "-h"|"--help")
      shift;
      help=true
      break;;
    *)
      break;;
  esac
done

if test $help; then
  usage
  exit 1
fi

\# Deprecated (since cmake 3.12) variables from the FindPythonInterp
\# PYTHONINTERP_FOUND
\# PYTHON_EXECUTABLE
\# PYTHON_VERSION_STRING
\# PYTHON_VERSION_MAJOR
\# PYTHON_VERSION_MINOR
\# PYTHON_VERSION_PATCH
\# Additional deprecated (since cmake 3.12) variables from the FindPythonLibs
\# PYTHONLIBS_FOUND
\# PYTHON_LIBRARIES
\# PYTHON_INCLUDE_PATH
\# PYTHON_INCLUDE_DIRS
\# PYTHON_DEBUG_LIBRARIES
\# PYTHONLIBS_VERSION_STRING
\# PYTHON_LIBRARY
\# PYTHON_INCLUDE_DIR

cat > /tmp/temp.sed << EOF
s/PYTHON_LIBRARY_PATH/CTK_PYTHON3_LIBRARY_PATH/g
s/PYTHON_LIBRARY/CTK_PYTHON3_LIBRARY/g
s/PYTHON_INCLUDE_DIR/CTK_PYTHON3_INCLUDE_DIR/g
s/PYTHON_DEBUG_LIBRARIES/CTK_PYTHON3_DEBUG_LIBRARIES/g
s/PYTHONINTERP_FOUND/Python3_Interpreter_FOUND/g
s/PYTHON_EXECUTABLE/Python3_EXECUTABLE/g
s/PYTHON_VERSION_STRING/Python3_VERSION/g
s/PYTHON_VERSION_MAJOR/Python3_VERSION_MAJOR/g
s/PYTHON_VERSION_MINOR/Python3_VERSION_MINOR/g
s/PYTHON_VERSION_PATCH/Python3_VERSION_PATCH/g
s/PYTHONLIBS_FOUND/Python3_Development_FOUND/g
s/PYTHON_LIBRARIES/Python3_LIBRARIES/g
s/PYTHON_INCLUDE_PATH/Python3_XXXXXXX_INCLUDE_PATH_NO_MAPPING_FOR_THIS_PYTHON.h_PATH_FINDER/g
s/PYTHON_INCLUDE_DIRS/Python3_INCLUDE_DIRS/g
s/PYTHON_DEBUG_LIBRARIES/Python3_XXXXX_NO_MAPPING_FOR_THIS_DEBUG_LIBRARIES_FLAG/g
s/PYTHONLIBS_VERSION_STRING/Python3_VERSION/g
s/PYTHON_LIBRARY/Python3_XXXXXX_LIBARY__NO_MAPPING_FOR_THIS_/g
s/PYTHON_INCLUDE_DIR/Python3_XXXXXXX_INCLUDE_DIR_NO_MAPPING_FOR_THIS_PYTHON.h_PATH_FINDER/g
s/find_package *( *PythonInterp *REQUIRED *)/find_package(Python3 COMPONENTS Interpreter REQUIRED)/g
s/find_package *( *PythonInterp *)/find_package(Python3 COMPONENTS Interpreter)/g
s/find_package *( *PythonLibs *)/find_package(Python3 COMPONENTS Development)/g
s/find_package *( *PythonInterp/find_package(Python3 COMPONENTS Interpreter/g
s/find_package *( *PythonLibs/find_package(Python3 COMPONENTS Development/g
s/below_restore_pattern_match_changes_to_original/values/g
s/____IGNORE_REVERSION_TO_ORIGINAL_VARIABLE_NAME_____CTK_PYTHON3_LIBRARY_PATH/PYTHON_LIBRARY_PATH/g
s/____IGNORE_REVERSION_TO_ORIGINAL_VARIABLE_NAME_____CTK_PYTHON3_LIBRARY/PYTHON_LIBRARY/g
s/____IGNORE_REVERSION_TO_ORIGINAL_VARIABLE_NAME_____CTK_PYTHON3_INCLUDE_DIR/PYTHON_INCLUDE_DIR/g
s/____IGNORE_REVERSION_TO_ORIGINAL_VARIABLE_NAME_____CTK_PYTHON3_DEBUG_LIBRARIES/PYTHON_DEBUG_LIBRARIES/g
EOF

if [ $(uname) == "Darwin" ] ; then
  SEDBIN=gsed
else
  SEDBIN=sed
fi

\# Do the replacement
find . -type f \( -name 'CMakeLists.txt' -o -name '*\.cmake*' \) -exec ${SEDBIN} -i''  -f /tmp/temp.sed {} \;

cat > /tmp/git_message.txt << EOF
${COMMIT_INFO}
EOF

Author: hjmjohnson

CMake/ctkBlockCheckDependencies.cmake

@@ -75,7 +75,7 @@ set(${Log4Qt_enabling_variable}_INCLUDE_DIRS Log4Qt_INCLUDE_DIRS)
 set(${Log4Qt_enabling_variable}_FIND_PACKAGE_CMD Log4Qt)
 
 set(PythonQt_enabling_variable PYTHONQT_LIBRARIES)
-set(${PythonQt_enabling_variable}_INCLUDE_DIRS PYTHONQT_INCLUDE_DIR PYTHON_INCLUDE_DIRS)
+set(${PythonQt_enabling_variable}_INCLUDE_DIRS PYTHONQT_INCLUDE_DIR CTK_PYTHON3_INCLUDE_DIRS)
 set(${PythonQt_enabling_variable}_FIND_PACKAGE_CMD PythonQt)
 
 set(QtSOAP_enabling_variable QtSOAP_LIBRARIES)

CMake/ctkMacroBuildLibWrapper.cmake

@@ -95,8 +95,8 @@ macro(ctkMacroBuildLibWrapper)
   # Since the PythonQt decorator depends on PythonQt, Python and VTK, let's link against
   # these ones to avoid complaints of MSVC
   # Note: "LINK_DIRECTORIES" has to be invoked before "ADD_LIBRARY"
-  ctkFunctionExtractOptimizedLibrary(PYTHON_LIBRARIES PYTHON_LIBRARY)
-  set(my_EXTRA_PYTHON_LIBRARIES ${PYTHON_LIBRARY} ${PYTHONQT_LIBRARIES})
+  ctkFunctionExtractOptimizedLibrary(Python3_LIBRARIES CTK_PYTHON3_LIBRARY)
+  set(my_EXTRA_Python3_LIBRARIES ${CTK_PYTHON3_LIBRARY} ${PYTHONQT_LIBRARIES})
 
   # Does a header having the expected filename exists ?
   string(REGEX REPLACE "^CTK" "ctk" lib_name_lc_ctk ${lib_name})
@@ -127,7 +127,7 @@ macro(ctkMacroBuildLibWrapper)
     endif()
   endif()
   add_library(${lib_name}PythonQt ${MY_WRAPPER_LIBRARY_TYPE} ${KIT_PYTHONQT_SRCS})
-  target_link_libraries(${lib_name}PythonQt ${lib_name} ${my_EXTRA_PYTHON_LIBRARIES})
+  target_link_libraries(${lib_name}PythonQt ${lib_name} ${my_EXTRA_Python3_LIBRARIES})
   if(MY_WRAPPER_LIBRARY_TYPE STREQUAL "STATIC")
     if(CMAKE_SIZEOF_VOID_P EQUAL 8) # 64-bit
       set_target_properties(${lib_name}PythonQt PROPERTIES COMPILE_FLAGS "-fPIC")

CMake/ctkMacroCompilePythonScript.cmake

@@ -148,19 +148,19 @@ function(_ctk_add_compile_python_directories_target target)
       set(_compileall_code "${_compileall_code}\nctk_compile_file('${tgt}', force=1)")
     endforeach()
 
-    if(NOT PYTHONINTERP_FOUND)
-      find_package(PythonInterp REQUIRED)
+    if(NOT Python3_Interpreter_FOUND)
+      find_package(Python3 COMPONENTS Interpreter REQUIRED)
     endif()
-    if(NOT PYTHONLIBS_FOUND)
-      find_package(PythonLibs REQUIRED)
+    if(NOT Python3_Development_FOUND)
+      find_package(Python3 COMPONENTS Development REQUIRED)
     endif()
 
     # Extract python lib path
-    ctkFunctionExtractOptimizedLibrary(PYTHON_LIBRARIES PYTHON_LIBRARY)
-    get_filename_component(PYTHON_LIBRARY_PATH "${PYTHON_LIBRARY}" PATH)
+    ctkFunctionExtractOptimizedLibrary(Python3_LIBRARIES CTK_PYTHON3_LIBRARY)
+    get_filename_component(CTK_PYTHON3_LIBRARY_PATH "${CTK_PYTHON3_LIBRARY}" PATH)
 
     # Configure cmake script associated with the custom command
-    # required to properly update the library path with PYTHON_LIBRARY_PATH
+    # required to properly update the library path with CTK_PYTHON3_LIBRARY_PATH
     set(compile_all_cmake_script "${CMAKE_CURRENT_BINARY_DIR}/compile_${target}_python_scripts.cmake")
     configure_file(
       ${CTK_CMAKE_DIR}/ctk_compile_python_scripts.cmake.in

CMake/ctkMacroWrapPythonQt.cmake

@@ -62,10 +62,10 @@ macro(ctkMacroWrapPythonQt WRAPPING_NAMESPACE TARGET SRCS_LIST_NAME SOURCES IS_W
   # TODO: this find package seems not to work when called form a superbuild, but the call is needed
   # in general to find the python interpreter.  In CTK, the toplevel CMakeLists.txt does the find
   # package so this is a no-op.  Other uses of this file may need to have this call so it is still enabled.
-  if(NOT PYTHONINTERP_FOUND)
-    find_package(PythonInterp)
-    if(NOT PYTHONINTERP_FOUND)
-      message(FATAL_ERROR "PYTHON_EXECUTABLE not specified or inexistent when calling ctkMacroWrapPythonQt")
+  if(NOT Python3_Interpreter_FOUND)
+    find_package(Python3 COMPONENTS Interpreter)
+    if(NOT Python3_Interpreter_FOUND)
+      message(FATAL_ERROR "Python3_EXECUTABLE not specified or inexistent when calling ctkMacroWrapPythonQt")
     endif()
   endif()
 
@@ -157,7 +157,7 @@ macro(ctkMacroWrapPythonQt WRAPPING_NAMESPACE TARGET SRCS_LIST_NAME SOURCES IS_W
     DEPENDS
       ${SOURCES_TO_WRAP}
       ${CTK_CMAKE_DIR}/ctkWrapPythonQt.py
-    COMMAND ${PYTHON_EXECUTABLE} ${CTK_CMAKE_DIR}/ctkWrapPythonQt.py
+    COMMAND ${Python3_EXECUTABLE} ${CTK_CMAKE_DIR}/ctkWrapPythonQt.py
       --target=${TARGET}
       --namespace=${WRAPPING_NAMESPACE}
       --output-dir=${CMAKE_CURRENT_BINARY_DIR}/${wrap_int_dir} ${extra_args}
@@ -193,6 +193,6 @@ macro(ctkMacroWrapPythonQt WRAPPING_NAMESPACE TARGET SRCS_LIST_NAME SOURCES IS_W
   if(NOT PYTHONQT_FOUND)
     message(FATAL_ERROR "error: PythonQt package is required to build ${TARGET}PythonQt")
   endif()
-  include_directories(${PYTHON_INCLUDE_DIRS} ${PYTHONQT_INCLUDE_DIR})
+  include_directories(${CTK_PYTHON3_INCLUDE_DIRS} ${PYTHONQT_INCLUDE_DIR})
 
 endmacro()

CMake/ctk_compile_python_scripts.cmake.in

@@ -85,15 +85,15 @@ file.write('Done')
 set(ENV{PYTHONPATH} "@CTK_PYTHON_COMPILE_FILE_SCRIPT_DIR@")
 
 if(WIN32)
-  set(ENV{PATH} "@PYTHON_LIBRARY_PATH@;$ENV{PATH}")
+  set(ENV{PATH} "@CTK_PYTHON3_LIBRARY_PATH@;$ENV{PATH}")
 elseif(APPLE)
-  set(ENV{DYLD_LIBRARY_PATH} "@PYTHON_LIBRARY_PATH@:$ENV{DYLD_LIBRARY_PATH}")
+  set(ENV{DYLD_LIBRARY_PATH} "@CTK_PYTHON3_LIBRARY_PATH@:$ENV{DYLD_LIBRARY_PATH}")
 else()
-  set(ENV{LD_LIBRARY_PATH} "@PYTHON_LIBRARY_PATH@:$ENV{LD_LIBRARY_PATH}")
+  set(ENV{LD_LIBRARY_PATH} "@CTK_PYTHON3_LIBRARY_PATH@:$ENV{LD_LIBRARY_PATH}")
 endif()
 
 execute_process(
-  COMMAND "@PYTHON_EXECUTABLE@" "@compile_all_script@"
+  COMMAND "@Python3_EXECUTABLE@" "@compile_all_script@"
   RESULT_VARIABLE result_var
   )
 if(NOT result_var STREQUAL 0)

CMakeExternals/PythonQt.cmake

@@ -73,14 +73,14 @@ if(NOT DEFINED PYTHONQT_INSTALL_DIR)
   endif()
 
   # Python is required
-  if(NOT PYTHONLIBS_FOUND)
-    find_package(PythonLibs)
-    if(NOT PYTHONLIBS_FOUND)
+  if(NOT Python3_Development_FOUND)
+    find_package(Python3 COMPONENTS Development)
+    if(NOT Python3_Development_FOUND)
       message(FATAL_ERROR "error: Python is required to build ${PROJECT_NAME}")
     endif()
   endif()
 
-  ctkFunctionExtractOptimizedLibrary(PYTHON_LIBRARIES PYTHON_LIBRARY)
+  ctkFunctionExtractOptimizedLibrary(Python3_LIBRARIES CTK_PYTHON3_LIBRARY)
   if(CTK_QT_VERSION VERSION_EQUAL "5")
     set(revision_tag c128afb1b72488e1c21b1cb0205b795b268b45d0) # patched-v3.6.1-2025-09-30-f4769f190
   else()
@@ -112,9 +112,9 @@ if(NOT DEFINED PYTHONQT_INSTALL_DIR)
     CMAKE_CACHE_ARGS
       ${ep_common_cache_args}
       -DPythonQt_QT_VERSION:STRING=${CTK_QT_VERSION}
-      -DPYTHON_INCLUDE_DIR:PATH=${PYTHON_INCLUDE_DIR}
-      -DPYTHON_INCLUDE_DIR2:PATH=${PYTHON_INCLUDE_DIR2}
-      -DPYTHON_LIBRARY:FILEPATH=${PYTHON_LIBRARY}
+      -DCTK_PYTHON3_INCLUDE_DIR:PATH=${CTK_PYTHON3_INCLUDE_DIR}
+      -DCTK_PYTHON3_INCLUDE_DIR2:PATH=${CTK_PYTHON3_INCLUDE_DIR2}
+      -DCTK_PYTHON3_LIBRARY:FILEPATH=${CTK_PYTHON3_LIBRARY}
       ${ep_PythonQt_args}
     DEPENDS
       ${${proj}_DEPENDENCIES}
@@ -145,10 +145,10 @@ set(PythonQt_DIR ${PYTHONQT_INSTALL_DIR})
 mark_as_superbuild(
   VARS
     PYTHONQT_INSTALL_DIR:PATH
-    PYTHON_EXECUTABLE:FILEPATH # FindPythonInterp expects PYTHON_EXECUTABLE variable to be defined
-    PYTHON_INCLUDE_DIR:PATH # FindPythonQt expects PYTHON_INCLUDE_DIR variable to be defined
-    PYTHON_INCLUDE_DIR2:PATH
-    PYTHON_LIBRARY:FILEPATH # FindPythonQt expects PYTHON_LIBRARY variable to be defined
+    Python3_EXECUTABLE:FILEPATH # FindPythonInterp expects Python3_EXECUTABLE variable to be defined
+    CTK_PYTHON3_INCLUDE_DIR:PATH # FindPythonQt expects CTK_PYTHON3_INCLUDE_DIR variable to be defined
+    CTK_PYTHON3_INCLUDE_DIR2:PATH
+    CTK_PYTHON3_LIBRARY:FILEPATH # FindPythonQt expects CTK_PYTHON3_LIBRARY variable to be defined
   LABELS "FIND_PACKAGE_VARS"
   )
 mark_as_superbuild(

CMakeExternals/VTK.cmake

@@ -68,24 +68,24 @@ if(NOT DEFINED VTK_DIR AND NOT ${CMAKE_PROJECT_NAME}_USE_SYSTEM_${proj})
   if(CTK_LIB_Scripting/Python/Core_PYTHONQT_USE_VTK)
 
     if(NOT DEFINED VTK_PYTHON_VERSION)
-      set(VTK_PYTHON_VERSION ${PYTHON_VERSION_MAJOR})
+      set(VTK_PYTHON_VERSION ${Python3_VERSION_MAJOR})
     endif()
-    if(NOT "${VTK_PYTHON_VERSION}" STREQUAL "${PYTHON_VERSION_MAJOR}")
-      message(FATAL_ERROR "error: VTK_PYTHON_VERSION [${VTK_PYTHON_VERSION}] is expected to match PYTHON_VERSION_MAJOR [${PYTHON_VERSION_MAJOR}]")
+    if(NOT "${VTK_PYTHON_VERSION}" STREQUAL "${Python3_VERSION_MAJOR}")
+      message(FATAL_ERROR "error: VTK_PYTHON_VERSION [${VTK_PYTHON_VERSION}] is expected to match Python3_VERSION_MAJOR [${Python3_VERSION_MAJOR}]")
     endif()
-    set(Python3_EXECUTABLE ${PYTHON_EXECUTABLE})
-    set(Python3_INCLUDE_DIR ${PYTHON_INCLUDE_DIR})
-    set(Python3_LIBRARY ${PYTHON_LIBRARY})
+    set(Python3_EXECUTABLE ${Python3_EXECUTABLE})
+    set(Python3_INCLUDE_DIR ${CTK_PYTHON3_INCLUDE_DIR})
+    set(Python3_LIBRARY ${CTK_PYTHON3_LIBRARY})
     find_package(Python3 COMPONENTS Interpreter Development)
 
-    ctkFunctionExtractOptimizedLibrary(PYTHON_LIBRARIES PYTHON_LIBRARY)
+    ctkFunctionExtractOptimizedLibrary(Python3_LIBRARIES CTK_PYTHON3_LIBRARY)
     list(APPEND additional_vtk_cmakevars
       -DVTK_PYTHON_VERSION:STRING=${VTK_PYTHON_VERSION}
       # FindPythonInterp, FindPythonLibs
-      -DPYTHON_EXECUTABLE:PATH=${PYTHON_EXECUTABLE}
-      -DPYTHON_INCLUDE_DIR:PATH=${PYTHON_INCLUDE_DIR}
-      -DPYTHON_LIBRARY:FILEPATH=${PYTHON_LIBRARY}
-      -DPYTHON_DEBUG_LIBRARIES:FILEPATH=${PYTHON_DEBUG_LIBRARIES}
+      -DPython3_EXECUTABLE:PATH=${Python3_EXECUTABLE}
+      -DCTK_PYTHON3_INCLUDE_DIR:PATH=${CTK_PYTHON3_INCLUDE_DIR}
+      -DCTK_PYTHON3_LIBRARY:FILEPATH=${CTK_PYTHON3_LIBRARY}
+      -DCTK_PYTHON3_DEBUG_LIBRARIES:FILEPATH=${CTK_PYTHON3_DEBUG_LIBRARIES}
       )
     # VTK9
     list(APPEND additional_vtk9_cmakevars

CMakeLists.txt

@@ -880,16 +880,16 @@ endif()
 
 # Check if dependencies are satisfied
 if(CTK_LIB_Scripting/Python/Core)
-  if(NOT PYTHONINTERP_FOUND)
-    find_package(PythonInterp)
-    if(NOT PYTHONINTERP_FOUND)
-      message(FATAL_ERROR "PYTHON_EXECUTABLE variable should be set to build CTK_LIB_Scripting/Python")
+  if(NOT Python3_Interpreter_FOUND)
+    find_package(Python3 COMPONENTS Interpreter)
+    if(NOT Python3_Interpreter_FOUND)
+      message(FATAL_ERROR "Python3_EXECUTABLE variable should be set to build CTK_LIB_Scripting/Python")
     endif()
   endif()
-  if(NOT PYTHONLIBS_FOUND)
-    find_package(PythonLibs)
-    if(NOT PYTHONLIBS_FOUND)
-      message(FATAL_ERROR "PYTHON_LIBRARIES and PYTHON_INCLUDE_DIRS should be set to build CTK_LIB_Scripting/Python")
+  if(NOT Python3_Development_FOUND)
+    find_package(Python3 COMPONENTS Development)
+    if(NOT Python3_Development_FOUND)
+      message(FATAL_ERROR "Python3_LIBRARIES and CTK_PYTHON3_INCLUDE_DIRS should be set to build CTK_LIB_Scripting/Python")
     endif()
   endif()
 endif()

Libs/Scripting/Python/Core/CMakeLists.txt

@@ -41,7 +41,7 @@ configure_file(
 
 # Target libraries - See CMake/ctkFunctionGetTargetLibraries.cmake
 # The following macro will read the target libraries from the file 'target_libraries.cmake'
-ctkFunctionExtractOptimizedLibrary(PYTHON_LIBRARIES PYTHON_LIBRARY)
+ctkFunctionExtractOptimizedLibrary(Python3_LIBRARIES CTK_PYTHON3_LIBRARY)
 ctkFunctionGetTargetLibraries(KIT_target_libraries)
 
 ctkMacroBuildLib(

Libs/Scripting/Python/Core/target_libraries.cmake

@@ -5,7 +5,7 @@
 #
 
 set(target_libraries
-  PYTHON_LIBRARY
+  CTK_PYTHON3_LIBRARY
   PYTHONQT_LIBRARIES
   CTKCore
   )