On 4/10/22 01:56, Farley, Peter x23353 wrote:
I have read that tagging behavior page and it makes sense when applied to files stored in
the Unix file system. MVS datasets could just as easily just be considered always tagged
as cp1047 (with an option to change the CCSID to 037 or one of the European EBCIDIC code
pages) and then you just go on from there. Connecting to the MVS file system "under
the covers" is the runtime implementor's job, not the application developer's job.
As to providing a package to specifically access MVS datasets, my first question is why IBM didn't
provide one in the first place, or better yet build it into the python I/O subsystem from the
start? Why does the community need to provide such a basic functionality? "zoautil_py"
is one such implementation, but it is extraordinarily "heavyweight" and expensive to use,
and is not an acceptable solution in a world where every second counts and costs real money.
I am quite sure an MVS I/O package will happen just like it did for
golang and Node.js. Yet again, open source code documented in Github and
the respective package manager repositories. You may not like that but
it's how these things work.
https://github.com/ibmruntimes/go-recordio
The lack of easy-to-use and efficient MVS file access may well discourage more
widespread use of python on z/OS for everyday computing tasks.
Maybe not as much as you think. The tooling coming online will require
Python so it's mandatory. The vast majority on this forum would rather
use REXX anyway!
And yes, I can accept that my expectations are not realistic. It is just a shame that an
easy-to-use and efficient access to MVS datasets isn't and won't be there unless the
"community" provides it. IMHO it should have been part-and-parcel of the
original language implementation, but I know what my opinions and expectations are worth.
The community involves IBM and the team that ported Python, Golang,
Node.js etc. The team from IBM Toronto have setup and open source
community that are actively ported FOSS to z/OS. Interestingly, this
includes the zsh which I'm delighted about.
Peter
-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of
David Crayford
Sent: Monday, October 3, 2022 1:48 AM
To: [email protected]
Subject: Re: IBM python documentation? [was: RE: IBM SMF Export with Python]
On 3/10/22 07:18, Farley, Peter x23353 wrote:
Where, for instance, in the documentation that you linked to is there information on
whether the python "open()" function for files will or will not support direct
access to MVS datasets without transferring them down to the Unix file system? I.E.,
are either of these calls to the open() function valid or not:
Myfile = open("//'MVS.DATA.SET.NAME", "rt", ccsid="1047")
Myfile = open("//:DDNAME", "rt", ccsid="1047") # This of course
assumes that a call to "bpxunix" (or by other means) has been used to
establish a DD allocation in the AS where the python program is
executing
This will *never* happen. If you read the doc WRT tagging behaviors you will
understand why
https://urldefense.com/v3/__https://www.ibm.com/docs/en/python-zos/3.9?topic=translation-tagging-behaviors__;!!Ebr-cpPeAnfNniQ8HSAI-g_K5b7VKg!O2czdpcmZt_bBNIuRr4UXedStf34QpBfTBkZ-wQNwNFosWZR2zrDSP1nat8ZFfmZnRA9s7TVhDN6jaUYFy-CaGg$
.
Rocket's Python port supported reading MVS data sets but it was not a
documented feature and was used with great care. Patching the Python core I/O
libraries to support MVS data sets is not a great idea. It's much better to
write a specific library that *only* support MVS data sets and not z/OS UNIX
files. A good reference implementation is the JZOS ZFile class. If you open an
RFE IBM may do this. Or maybe the community can contribute? Either way it's
going to be implemented as a specific package.
Porting tools to support MVS data sets in trivial. They use open() because it's
a low-level API and read/write support sockets, FIFO's, pipes etc. It's not
just a case of replacing open with fopen(). Python implements a fdopen()
https://urldefense.com/v3/__https://docs.python.org/3/library/os.html*os.fdopen__;Iw!!Ebr-cpPeAnfNniQ8HSAI-g_K5b7VKg!O2czdpcmZt_bBNIuRr4UXedStf34QpBfTBkZ-wQNwNFosWZR2zrDSP1nat8ZFfmZnRA9s7TVhDN6jaUY6MzWLWc$
method for wrapping
file descriptors.
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