[CMake] Finding Python Modules with CMake

[Mark Moll]

On Jan 3, 2011, at 2:17 AM, Todd Gamblin wrote:

> Is there a way in CMake, once I find the python interpreter, to query for the availability of a particular module?  e.g. say I want to make sure that the host's python installation has PyQt4, or numy, or something like that.  Do I have to manually run the interpreter, try to import it, and check the return code, or is there a builtin for that?
> 
> Something like this would be handy for the python modules:
> 
> 	http://www.gnu.org/software/autoconf-archive/ax_python_module.html
> 
> Again, I couldn't find much in the docs for this.
> 

Yes. I wrote this function (which relies on PYTHON_EXEC pointing to the python executable):

function(find_python_module module)
	string(TOUPPER ${module} module_upper)
	if(NOT PY_${module_upper})
		if(ARGC GREATER 1 AND ARGV1 STREQUAL "REQUIRED")
			set(${module}_FIND_REQUIRED TRUE)
		endif()
		# A module's location is usually a directory, but for binary modules
		# it's a .so file.
		execute_process(COMMAND "${PYTHON_EXEC}" "-c" 
			"import re, ${module}; print re.compile('/__init__.py.*').sub('',${module}.__file__)"
			RESULT_VARIABLE _${module}_status 
			OUTPUT_VARIABLE _${module}_location
			ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
		if(NOT _${module}_status)
			set(PY_${module_upper} ${_${module}_location} CACHE STRING 
				"Location of Python module ${module}")
		endif(NOT _${module}_status)
	endif(NOT PY_${module_upper})
	find_package_handle_standard_args(PY_${module} DEFAULT_MSG PY_${module_upper})
endfunction(find_python_module)


You can then write:

find_python_module(PyQt4 REQUIRED)


-- 
Mark Moll