[CMake] Installing Python files

[Hendrik Sattler]

Am 2013-03-27 05:46, schrieb Steve Andrews:
> Thats very helpful.  Thank you.
>
> My other question was about how to get CMake to create directories at
> installation time.  Do you, or someone else, have suggestions about
> that?  Despite your advice, I think that I want the "make install"
> step to put Python files into
> /usr/local/lib/python2.5/site-packages/moleculizer, at least as the
> default path.  Depending on what the users system already has, I may
> need to create one or more levels of this hierarchy.  Do you know if
> there is a way to create this directory structure, as needed, during
> the install step?
>
> Thanks,
> -Steve
>
> On Tue, Mar 26, 2013 at 4:28 PM, Andreas Pakulat <apaku at gmx.de [1]>
> wrote:
>
>> Hi,
>>
>> Am Dienstag, 26. März 2013 schrieb sandrews :
>>
>>> Hi,
>>>
>>> My project is primarily C and C++, but also includes some Python
>>> code.  I
>>> can get everything to build fine, and my CMakeLists.txt files
>>> uses the
>>> INSTALL(TARGETS ...) to so that the user can install the compiled
>>> code to
>>> the proper place.  However, part of the installation is to copy
>>> the Python
>>> files over to their proper places, too, and this isnt working.
>>>
>>> First of all, where should Python files go?  On my Mac, I put
>>> them in
>>> /usr/local/lib/python2.5/site-packages.  Of course though, this
>>> directory
>>> would be different if I had a different version of Python.
>>>  Also, I expect
>>> its different on different platforms.  Does CMake automatically
>>> know where
>>> the Python files should go and, if so, how do I access that?
>>>  (For example,
>>> the INSTALL(TARGETS...) command does know where targets are
>>> supposed to go
>>> for different platforms.)
>>
>>  
>> No, cmake does not know about this as python apps are usually
>> installed with python tools like distutils, setuptools etc. That
>> beingsaid cmake does ship modules to find a python interpreter and
>> that one can be queried about its search path. Along with the
>> install command (using the FILES variant) you can have cmake copy
>> your python code where you want it.
>>
>> However you should think twice before writing cmake code that
>> installs stuff outside thecmake prefix. This is usually unexpected
>> by cmake users, can turn out to be impossible (the user might not be
>> able to writeto thepython install directory) or trip up packaging
>> tools (such as cpack).
>>
>> On the other hand, having python files in something like $HOME/myapp
>> does require an extra environment variable to be set in order for
>> python to find the code there. Thats something that python users are
>> possibly used to though.

I had the same problem when trying to find a proper location for 
installing
a SWIG Python module. CMake helps building it but lacks on the 
installation
part :-/

I did it like this:
find_package ( PythonLibs REQUIRED )
find_package ( PythonInterp REQUIRED )

if ( PYTHON_VERSION_STRING AND PYTHONLIBS_VERSION_STRING )
   if ( NOT PYTHON_VERSION_STRING VERSION_EQUAL 
PYTHONLIBS_VERSION_STRING )
     message ( FATAL_ERROR
             "Version mismatch between python interpreter and libraries" 
)
   endif ( NOT PYTHON_VERSION_STRING VERSION_EQUAL 
PYTHONLIBS_VERSION_STRING )
endif ( PYTHON_VERSION_STRING AND PYTHONLIBS_VERSION_STRING )

include_directories ( ${PYTHON_INCLUDE_DIRS} )

....target..setup....

execute_process (
   COMMAND ${PYTHON_EXECUTABLE} -c
   	"import site, sys; sys.stdout.write(site.PREFIXES[-1])"
   OUTPUT_VARIABLE PYTHON_PREFIX
)
file ( TO_CMAKE_PATH "${PYTHON_PREFIX}" PYTHON_PREFIX )
execute_process (
   COMMAND ${PYTHON_EXECUTABLE} -c
   	"import site, sys; sys.stdout.write(site.getsitepackages()[-1])"
   OUTPUT_VARIABLE PYTHON_SITE_DIR
)
file ( TO_CMAKE_PATH "${PYTHON_SITE_DIR}" PYTHON_SITE_DIR )
string ( REGEX REPLACE "^${PYTHON_PREFIX}/" ""
   PYTHON_SITE_DIR "${PYTHON_SITE_DIR}"
)

install ( TARGETS ${SWIG_MODULE_obexftp-python_REAL_NAME}
   LIBRARY
     DESTINATION ${PYTHON_SITE_DIR}
     COMPONENT library
)

install ( FILES ${CMAKE_CURRENT_BINARY_DIR}/obexftp.py
   DESTINATION ${PYTHON_SITE_DIR}
   COMPONENT library
)


My setup is similar for Perl and Ruby SWIG modules as the problem is 
the same
there.

HS