forum.vmspython.org

[EvanJohn]

I have read that Cython will allow extension modules to be combined into packages. I am having a lot of trouble doing this in the VMS environment.

This is hot helped by the fact that the setup() and cythonize() functions are useless in the VMS environment. Perhaps if I could get them working it would solve my problem. Personally I find it much easier to simply use build command lines and MMS.

When I use "$ python setup.py build_ext -v -n" the link command generated is not usable, and the C compiler is invoked via "mc cc" - which is really weird. This does not worry me too much so that I can create a package and link it using the "cython", "cc" and "link" commands "au naturel".

[bisonmalembouche]

You should have a look at

https://repos.sysgroup.fr/OpenVMS/vmspython/raw/7ebb52adc47ff89c9a25a6cc8bfec0688cd38283/python/local/vms/starlet/_starlet.c

and

https://repos.sysgroup.fr/OpenVMS/vmspython/files/dd352f166893e10ee6a1eed688e6c239400b2e04/python/local/vms/rtl/lib/build_lib_module.com

[EvanJohn]

I gather from the two links that starlet is a module and vms is a package.

I am interested in the package - which is vms, not starlet. My questions are:

Was the vmslib C code generated by Cython or was it hand coded? In either case I need to look at the source.

How are the individual modules - like starlet - linked to the vms package? Are they in the same image? It looks like they are not in the same C compilation (and the same object file) but I guess it is possible. If they are in separate images do they use the same "init..." symbol names?

[EvanJohn]

I had a look at the VMS package a bit more carefully. This is how I think it works:

Each extension module has a straight PY wrapper. E.g. the ptd extension module is called _vmsptd and has a wrapper which is __init__.py in the directory python_root:[local.vms.ptd]. This __init__ defines the wrapper class "Ptd".

The extension, meanwhile, is called _vmsptd and is provided by _vmsptd.exe in the same directory, with the entry-point init_vmsptd.

I think, therefore, the answer to my question is that extension modules are grouped into packages using standard py - directories and classes. The standard py wraps the underlying extension modules which reside in the same directories.

[bisonmalembouche]

There is a Python script: python_vms:build_module.py that takes a module name as P1 (case sensitive) , and generates the shareable for this C module.

latest version
https://repos.sysgroup.fr/OpenVMS/cpython27/files/5fe77cb382a7eea60bae2d89eead74360300e6ba/vms/build_module.py

You can adapt this module to automatically build Cython modules, it should not be difficult.

[EvanJohn]

Thanks for that. I discovered that the main thing I was missing was the __init__.py file in the package directory. This allows the module shareable images to be found using the package (directory) name. (I am a complete beginner at Python, unfortunately.)

All cool. It works really well. Thanks for the help.

PS I have previously tried to export "native" functionality to PHP. This is extremely tedious. Cython makes this kind of thing possible - and efficient.

[bisonmalembouche]

Hello

JFP has written a vms/build_cython_module.py that is available at

https://repos.sysgroup.fr/OpenVMS/cpython27/changeset/e30725302ec576c60ab0a9df7e74c89143cd2269

and will be in the next Python kit.