Using Pylint Tool to Test the python tutorial codes

* Adding CMake script to check if pylint is installed
* Adding Pylint config file (to choose the tests that are enabled)
* Adding CMake script to samples/python/tutorial_code

Testing: bad-indentation, mixed-indentation, unnecessary-semicolon, unused-variable

cmake/FindPylint.cmake

+# - Find Pylint
+# Find the Pylint executable and extract the version number
+#
+# OUTPUT Variables
+#
+#   PYLINT_FOUND
+#       True if the pylint package was found
+#   PYLINT_EXECUTABLE
+#       The pylint executable location
+#   PYLINT_VERSION
+#       A string denoting the version of pylint that has been found
+
+find_program(PYLINT_EXECUTABLE pylint PATHS /usr/bin)
+
+if(PYLINT_EXECUTABLE)
+  execute_process(COMMAND ${PYLINT_EXECUTABLE} --version OUTPUT_VARIABLE PYLINT_VERSION_RAW ERROR_QUIET)
+  if (PYLINT_VERSION_RAW)
+    string(REGEX REPLACE "^pylint ([0-9]+.[0-9]+.[0-9]+),.*" "\\1" PYLINT_VERSION ${PYLINT_VERSION_RAW})
+  else()
+    set(PYLINT_VERSION "unknown")
+  endif()
+endif()
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(Pylint DEFAULT_MSG PYLINT_EXECUTABLE)
+
+mark_as_advanced(PYLINT_EXECUTABLE PYLINT_VERSION)

doc/tutorials/introduction/documenting_opencv/documentation_tutorial.markdown

@@ -43,6 +43,10 @@ Generate documentation {#tutorial_documentation_generate}
     make doxygen
     @endcode
 -   Open <i>doc/doxygen/html/index.html</i> file in your favorite browser
+-   Test your python code:
+    @code{.sh}
+    make run_pylint_on_tutorials
+    @endcode
 
 Quick start {#tutorial_documentation_quick_start}
 ===========
@@ -600,7 +604,8 @@ Document the function {#tutorial_documentation_steps_fun}
 6. _Optional_: describe return value of the function using the _returns_ command.
 7. _Optional_: add "See also" section with links to similar functions or classes
 8. _Optional_: add bibliographic reference if any.
-9. Generate doxygen documentation and verify results.
+9. Test your code. (Python: "make run_pylint_on_tutorials")
+10. Generate doxygen documentation and verify results.
 
 Write the tutorial {#tutorial_documentation_steps_tutorial}
 ------------------

samples/CMakeLists.txt

@@ -12,6 +12,7 @@ if(NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_LIST_DIR)
 
 add_subdirectory(cpp)
 add_subdirectory(java/tutorial_code)
+add_subdirectory(python/tutorial_code)
 add_subdirectory(dnn)
 add_subdirectory(gpu)
 add_subdirectory(tapi)

samples/python/tutorial_code/CMakeLists.txt

+# ----------------------------------------------------------------------------
+#  CMake file to run pylint on the tutorial python files.
+#
+# ----------------------------------------------------------------------------
+include(${CMAKE_SOURCE_DIR}/cmake/FindPylint.cmake)
+
+project(run_pylint_on_tutorials)
+
+if(PYLINT_FOUND)
+  message(STATUS "pylint version: ${PYLINT_VERSION}")
+  set(curdir "${CMAKE_CURRENT_SOURCE_DIR}")
+  file(GLOB_RECURSE PYTHON_SCRIPTS ${curdir}/*.py)
+  add_custom_target("${PROJECT_NAME}")
+
+  foreach(SCRIPT ${PYTHON_SCRIPTS})
+    get_filename_component(SCRIPT_NAME ${SCRIPT} NAME_WE)
+    add_custom_command(TARGET "${PROJECT_NAME}"
+                       COMMAND ${PYLINT_EXECUTABLE} ${SCRIPT}
+                            --rcfile=${curdir}/pylintrc
+                       COMMENT "Running pylint on : ${SCRIPT_NAME}.py"
+                      )
+  endforeach()
+endif()

samples/python/tutorial_code/pylintrc

+[MESSAGES CONTROL]
+
+# Disable all to choose the Tests one by one
+disable=all
+
+# Tests
+enable=bad-indentation,       # Used when an unexpected number of indentation’s tabulations or spaces has been found.
+       mixed-indentation,     # Used when there are some mixed tabs and spaces in a module.
+       unnecessary-semicolon, # Used when a statement is ended by a semi-colon (”;”), which isn’t necessary.
+       unused-variable        # Used when a variable is defined but not used. (Use _var to ignore var).
+
+
+[REPORTS]
+
+# Activate the evaluation score.
+score=no