COMP: 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

Author: hjmjohnson

CMake/FindNumPy.cmake

@@ -17,11 +17,10 @@
 # all listed variables are TRUE
 
 if(NOT NUMPY_FOUND)
-  find_package(PythonInterp)
-  find_package(PythonLibs)
+  find_package(Python3 COMPONENTS Interpreter Development)
 
-  if(PYTHON_EXECUTABLE)
-    execute_process(COMMAND "${PYTHON_EXECUTABLE}"
+  if(Python3_EXECUTABLE)
+    execute_process(COMMAND "${Python3_EXECUTABLE}"
       -c "import numpy; print(numpy.get_include())"
       OUTPUT_VARIABLE _numpy_include_dir
       OUTPUT_STRIP_TRAILING_WHITESPACE
@@ -30,9 +29,11 @@ if(NOT NUMPY_FOUND)
   endif()
 endif()
 
+set(_numpy_search_paths ${Python3_INCLUDE_DIRS})
+list(prepend _numpy_search_paths "${_numpy_include_dir}")
 find_path(NUMPY_INCLUDE_DIR
   numpy/arrayobject.h
-  PATHS "${_numpy_include_dir}" "${PYTHON_INCLUDE_DIR}"
+  PATHS ${_numpy_search_paths}
   PATH_SUFFIXES numpy/core/include
   )
 

CMake/FindSphinx.cmake

@@ -6,9 +6,9 @@
 #  SPHINX_FOUND
 
 set(_python_paths )
-find_package(PythonInterp)
-if(PYTHON_EXECUTABLE)
-  get_filename_component(_python_dir "${PYTHON_EXECUTABLE}" DIRECTORY)
+find_package(Python3 COMPONENTS Interpreter)
+if(Python3_EXECUTABLE)
+  get_filename_component(_python_dir "${Python3_EXECUTABLE}" DIRECTORY)
   list(APPEND _python_paths
     "${_python_dir}"
     "${_python_dir}/bin"

CMake/ITKDoxygenTAG.cmake

@@ -1,11 +1,11 @@
 set( ITKDoxygenTAG_DIR ${CMAKE_BINARY_DIR}/ITKDoxygenTAG )
 set( ITKDoxygenTAG_TEMP_DIR ${CMAKE_BINARY_DIR}/ITKDoxygenTAG-TEMP )
 
-find_package(PythonInterp REQUIRED)
+find_package(Python3 COMPONENTS Interpreter REQUIRED)
 
 add_custom_command( OUTPUT ${ITKDoxygenTAG_DIR}/InsightDoxygen.tag
   COMMAND ${CMAKE_COMMAND} -DITKDoxygenTAG_TEMP_DIR="${ITKDoxygenTAG_TEMP_DIR}" -P ${CMAKE_CURRENT_SOURCE_DIR}/CMake/DownloadDoxygenTAG.cmake
-  COMMAND ${PYTHON_EXECUTABLE} "${ITKSphinxExamples_SOURCE_DIR}/Utilities/GUnzip.py" "${ITKDoxygenTAG_TEMP_DIR}/InsightDoxygen.tag.gz"
+  COMMAND ${Python3_EXECUTABLE} "${ITKSphinxExamples_SOURCE_DIR}/Utilities/GUnzip.py" "${ITKDoxygenTAG_TEMP_DIR}/InsightDoxygen.tag.gz"
 
   COMMAND ${CMAKE_COMMAND} -E remove_directory "${ITKDoxygenTAG_DIR}"
   COMMAND ${CMAKE_COMMAND} -E rename "${ITKDoxygenTAG_TEMP_DIR}" "${ITKDoxygenTAG_DIR}"

CMake/ITKSphinxExamplesMacros.cmake

@@ -18,7 +18,7 @@ macro(add_example example_name)
   if(BUILD_DOCUMENTATION)
     if(SPHINX_HTML_OUTPUT)
       add_custom_target(${example_name}DownloadableArchive
-        COMMAND ${PYTHON_EXECUTABLE} ${ITKSphinxExamples_SOURCE_DIR}/Utilities/CreateDownloadableArchive.py
+        COMMAND ${Python3_EXECUTABLE} ${ITKSphinxExamples_SOURCE_DIR}/Utilities/CreateDownloadableArchive.py
           ${example_name} ${SPHINX_DESTINATION}
         WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
         COMMENT "Creating downloadable archive for ${example_name}"

CMakeLists.txt

@@ -138,14 +138,21 @@ foreach(link ${content_links})
 endforeach()
 ExternalData_Add_Target(ITKSphinxExamplesData)
 
-if(${ITK_WRAP_PYTHON})
-  # Use the same Python interpreter as ITK to run the tests.
-  find_package(PythonInterp ${ITK_WRAP_PYTHON_VERSION} REQUIRED)
-  mark_as_advanced(PYTHON_EXECUTABLE)
+set(PYTHON_REQUIRED_VERSION 3.6)
+set(Python_ADDITIONAL_VERSIONS 3.12 3.11 3.10 3.9 3.8 3.7 3.6)
+if(BUILD_TESTING OR ITK_BUILD_DOCUMENTATION OR ITK_WRAP_PYTHON)
+  if(ITK_WRAP_PYTHON)
+    # Use the same Python interpreter as ITK to run the tests.
+    find_package(Python3 ${ITK_WRAP_PYTHON_VERSION} EXACT COMPONENTS Interpreter REQUIRED)
+    mark_as_advanced(Python3_EXECUTABLE)
+  else()
+    find_package(Python3 ${PYTHON_REQUIRED_VERSION} COMPONENTS Interpreter)
+  endif()
 endif()
-find_package(PythonInterp)
-if(PYTHON_EXECUTABLE AND NOT ITK_WRAP_PYTHON)
-  execute_process(COMMAND ${PYTHON_EXECUTABLE} -c "import itk"
+
+if(Python3_EXECUTABLE AND NOT ITK_WRAP_PYTHON)
+  # See if external ITK python packages are installed for this python environment
+  execute_process(COMMAND ${Python3_EXECUTABLE} -c "import itk"
     RESULT_VARIABLE _have_itk_return_code
     OUTPUT_QUIET
     ERROR_QUIET
@@ -154,62 +161,6 @@ if(PYTHON_EXECUTABLE AND NOT ITK_WRAP_PYTHON)
     set(ITK_WRAP_PYTHON 1)
   endif()
 endif()
-if(BUILD_TESTING OR ITK_BUILD_DOCUMENTATION OR ITK_WRAP_PYTHON)
-  # Prefer to use more robust FindPython3 module if greater than cmake 3.12.0
-  if("${CMAKE_VERSION}" VERSION_LESS_EQUAL "3.12.0")
-    # Use of PythonInterp and PythonLibs is deprecated since cmake version 3.12.0
-    # Only use deprecated mechanisms for older versions of cmake
-    set(Python_ADDITIONAL_VERSIONS 3.9 3.8 3.7 3.6 3.5)
-    find_package(PythonInterp)
-    if(ITK_WRAP_PYTHON)
-      find_package(PythonLibs REQUIRED)
-      # check for version mismatch.
-      if(PYTHONLIBS_FOUND AND PYTHONINTERP_FOUND
-          AND NOT(PYTHON_VERSION_STRING VERSION_EQUAL PYTHONLIBS_VERSION_STRING))
-        message(FATAL_ERROR "Python executable (\"${PYTHON_VERSION_STRING}\") and library (\"${PYTHONLIBS_VERSION_STRING}\") version mismatch.")
-      endif()
-    endif()
-    if(PYTHON_VERSION_STRING VERSION_LESS 3.5)
-      # if python version is less than 3.5, unset so that it appears that no python version is found.
-      # to emulate the same behavior as find(Python3 ..) from cmake 3.12.0+
-      unset(PYTHON_EXECUTABLE)
-      unset(PYTHONINTERP_FOUND)
-      unset(PYTHON_VERSION_STRING)
-      unset(PYTHON_INCLUDE_DIRS)
-    else()
-      ## For forward compatibility with cmake 3.12.0 or greater, emulate variable names from FindPython3.cmake
-      set(Python3_EXECUTABLE ${PYTHON_EXECUTABLE})
-      set(Python3_Interpreter_FOUND ${PYTHONINTERP_FOUND})
-      set(Python3_VERSION ${PYTHON_VERSION_STRING})
-
-      set(Python3_Development_FOUND ${PYTHONLIBS_FOUND})
-      set(Python3_INCLUDE_DIRS ${PYTHON_INCLUDE_DIRS})
-      set(Python3_LIBRARIES    ${PYTHON_LIBRARIES})
-    endif()
-  else()
-    if(ITK_WRAP_PYTHON)
-      if(DEFINED Python3_EXECUTABLE)
-        set(_specified_Python3_EXECUTABLE ${Python3_EXECUTABLE})
-      endif()
-      find_package(Python3 COMPONENTS Interpreter Development)
-      set(Python3_EXECUTABLE ${_specified_Python3_EXECUTABLE} CACHE INTERNAL
-        "Path to the Python interpreter" FORCE)
-    else()
-      find_package(Python3 COMPONENTS Interpreter)
-    endif()
-    if(NOT Python3_EXECUTABLE AND _Python3_EXECUTABLE)
-      set(Python3_EXECUTABLE ${_Python3_EXECUTABLE} CACHE INTERNAL
-        "Path to the Python interpreter" FORCE)
-    endif()
-  endif()
-
-  if(ITK_WRAP_PYTHON AND Python3_VERSION VERSION_LESS 3.5)
-    message(FATAL_ERROR "Python versions less than 3.5 are not supported for wrapping. Python version: \"${Python3_VERSION}\".")
-  endif()
-  if(ITK_WRAP_PYTHON AND NOT Python3_INCLUDE_DIRS)
-    message(FATAL_ERROR "Python version ${Python3_VERSION} development environment not found for wrapping.")
-  endif()
-endif()
 
 # Build the documentation?
 option(BUILD_DOCUMENTATION "Build the examples documentation." OFF)
@@ -265,7 +216,6 @@ if(BUILD_DOCUMENTATION)
   endif()
 
   # Builds the documentation.
-  find_package(PythonInterp REQUIRED)
   find_package(Sphinx REQUIRED)
   find_program(PANDOC_BIN pandoc REQUIRED)
 
@@ -288,7 +238,7 @@ if(BUILD_DOCUMENTATION)
       )
     add_custom_command(TARGET ${sphinx_target_base_name}_html
       POST_BUILD
-      COMMAND ${PYTHON_EXECUTABLE}
+      COMMAND ${Python3_EXECUTABLE}
         ${ITKSphinxExamples_SOURCE_DIR}/Utilities/DocumentationTarball.py
         ${SPHINX_DESTINATION}/html
         ${ITKSphinxExamples_BINARY_DIR}/ITKSphinxExamples-${ITKSphinxExamples_RELEASE_VERSION}-html

Superbuild/External-Python.cmake

@@ -1,12 +1,13 @@
-find_package(PythonInterp 3 REQUIRED)
+set(MIN_PYTHON_VERSION 3.5)
+find_package(Python3 ${MIN_PYTHON_VERSION} COMPONENTS Interpreter REQUIRED)
 
 set(_itk_venv "${CMAKE_CURRENT_BINARY_DIR}/itkpython")
 if(WIN32)
-  set(ITKPYTHON_EXECUTABLE "${_itk_venv}/python.exe" CACHE FILEPATH "Python executable with the ITK package installed" FORCE)
+  set(ITKPython3_EXECUTABLE "${_itk_venv}/python.exe" CACHE FILEPATH "Python executable with the ITK package installed" FORCE)
   set(SPHINX_EXECUTABLE "${_itk_venv}/Scripts/sphinx-build.exe" CACHE FILEPATH "Sphinx executable" FORCE)
   set(BLACK_EXECUTABLE "${_itk_venv}/Scripts/black.exe" CACHE FILEPATH "black executable" FORCE)
 else()
-  set(ITKPYTHON_EXECUTABLE "${_itk_venv}/bin/python" CACHE FILEPATH "Python executable with the ITK package installed" FORCE)
+  set(ITKPython3_EXECUTABLE "${_itk_venv}/bin/python" CACHE FILEPATH "Python executable with the ITK package installed" FORCE)
   set(SPHINX_EXECUTABLE "${_itk_venv}/bin/sphinx-build" CACHE FILEPATH "Sphinx executable" FORCE)
   set(BLACK_EXECUTABLE "${_itk_venv}/bin/black" CACHE FILEPATH "black executable" FORCE)
 endif()
@@ -15,8 +16,8 @@ configure_file("${CMAKE_CURRENT_SOURCE_DIR}/ITKBlackConfig.cmake.in"
 
 ExternalProject_Add(ITKPython
   DOWNLOAD_COMMAND ""
-  CONFIGURE_COMMAND ${PYTHON_EXECUTABLE} -m venv "${_itk_venv}"
-  BUILD_COMMAND ${ITKPYTHON_EXECUTABLE} -m pip install --upgrade pip
-  INSTALL_COMMAND ${ITKPYTHON_EXECUTABLE} -m pip install --ignore-installed itk>=5.3rc4 sphinx==4.4.0 docutils<0.18 six black nbsphinx ipython sphinx-contributors ipykernel matplotlib itkwidgets pydata-sphinx-theme
+  CONFIGURE_COMMAND ${Python3_EXECUTABLE} -m venv "${_itk_venv}"
+  BUILD_COMMAND ${ITKPython3_EXECUTABLE} -m pip install --upgrade pip
+  INSTALL_COMMAND ${ITKPython3_EXECUTABLE} -m pip install --ignore-installed itk>=5.3rc4 sphinx==4.4.0 docutils<0.18 six black nbsphinx ipython sphinx-contributors ipykernel matplotlib itkwidgets pydata-sphinx-theme
   COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/ITKBlackConfig.cmake
   )

Superbuild/External-VTK.cmake

@@ -5,7 +5,7 @@ if(NOT VTK_TAG)
   set(VTK_TAG "v9.0.1")
 endif()
 
-set(PYTHON_EXECUTABLE "${ITKPYTHON_EXECUTABLE}")
+set(Python3_EXECUTABLE "${ITKPython3_EXECUTABLE}")
 
 ExternalProject_Add(VTK
   GIT_REPOSITORY "https://gitlab.kitware.com/VTK/VTK.git"
@@ -23,7 +23,7 @@ ExternalProject_Add(VTK
     -DModule_vtkImagingMath:BOOL=ON
     -DVTK_WRAP_PYTHON:BOOL=ON
     -DExternalData_OBJECT_STORES:STRING=${ExternalData_OBJECT_STORES}
-    "-DPython3_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}"
+    "-DPython3_EXECUTABLE:FILEPATH=${Python3_EXECUTABLE}"
     -DVTK_USE_SYSTEM_ZLIB:BOOL=ON
     "-DZLIB_ROOT:PATH=${ZLIB_ROOT}"
     "-DZLIB_INCLUDE_DIR:PATH=${ZLIB_INCLUDE_DIR}"

Superbuild/Superbuild.cmake

@@ -50,10 +50,10 @@ if(WIN32)
   set(_use_python_default OFF)
 endif()
 option(ITKSphinxExamples_USE_WRAP_PYTHON "Enable downloads of the ITK Python wrapping to the superbuild" ${_use_python_default})
-if(NOT EXISTS PYTHON_EXECUTABLE AND ITKSphinxExamples_USE_WRAP_PYTHON OR ITKSphinxExamples_USE_VTK)
+if(NOT EXISTS Python3_EXECUTABLE AND ITKSphinxExamples_USE_WRAP_PYTHON OR ITKSphinxExamples_USE_VTK)
   include(${CMAKE_SOURCE_DIR}/External-Python.cmake)
   list(APPEND ITKSphinxExamples_DEPENDENCIES ITKPython)
-  set(_python_args "-DPYTHON_EXECUTABLE:FILEPATH=${ITKPYTHON_EXECUTABLE}")
+  set(_python_args "-DPython3_EXECUTABLE:FILEPATH=${ITKPython3_EXECUTABLE}")
 endif()
 
 if(NOT VTK_DIR AND ITKSphinxExamples_USE_VTK)

Utilities/CookieCutter/{{cookiecutter.example_name}}/CMakeLists.txt

@@ -33,10 +33,10 @@ add_test(NAME {{ cookiecutter.example_name }}Test
 )
 
 if(ITK_WRAP_PYTHON)
-  find_package(PythonInterp REQUIRED)
+  find_package(Python3 COMPONENTS Interpreter REQUIRED)
   string(REPLACE . "Python." output_image "${output_image}")
   add_test(NAME {{ cookiecutter.example_name }}TestPython
-    COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/Code.py
+    COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/Code.py
       ${input_image}
       ${output_image}
       ${test_options}

src/Bridge/NumPy/ConvertNumPyArrayToitkImage/CMakeLists.txt

@@ -11,7 +11,7 @@ set(input_image ${CMAKE_CURRENT_BINARY_DIR}/Slicer.png)
 
 if(ITK_WRAP_PYTHON)
   add_test(NAME  ConvertNumPyArrayToitkImageTestPython
-    COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/Code.py
+    COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/Code.py
     ${input_image}
     SliceRevised.png
     )