Installing python on z/OS.

I wanted to use Python on z/OS to run a REST workload. It took a bit of time, but it worked with no major problems.

As well as installing Python, I had to install some packages so I could use the request package to issue REST requests.

This page has a good article about using python on z/OS. I used it to install additional packages.

This post has topics

• Allocate a ZFS
• Format the ZFS
• Mount the ZFS
• Set up a profile
• Install the request package and co requisites

There is a Python from Rocket software, and one from IBM. They may be the same; I used the IBM version.

There are instructions here. I logged on to my usual IBM web site, where my usual browser remembered my userid and password, then used https://www.ibm.com/products/open-enterprise-python-zos/pricing .

I used the web site https://www.ibm.com/docs/en/python-zos/3.9?topic=configuration-installing-configuring-pax-edition.

When I used the web site directly, I had to enter my userid and password.

The web site has a .pax file, and instructions.

The HAMB390.runnable.pax.Z file used 492418 * 512 byte blocks on z/OS.

I did not have enough space in my ZFS on z/OS, so I had to allocate a new ZFS

Allocate a ZFS

//DEFINE EXEC PGM=IDCAMS
//SYSPRINT DD SYSOUT=*
//SYSIN DD *
DEFINE –
CLUSTER –
(NAME(COLIN.ZFS1 ) –
VOLUMES(USER00) –
LINEAR –
MEGABYTES(254 25) –
SHAREOPTIONS(3 3))
/*

Format it

//FORMATFS EXEC PGM=IOEAGFMT,REGION=0M,COND=(0,NE,DEFINE),
// PARM=(‘-aggregate COLIN.ZFS1 -compat’)
//SYSPRINT DD SYSOUT=*
//STDOUT DD SYSOUT=*
//STDERR DD SYSOUT=*
//*

Mount it

//MOUNT EXEC PGM=IKJEFT1A,COND=((0,NE,DEFINE),(0,NE,FORMATFS))
//SYSTSPRT DD SYSOUT=*
//SYSTSIN DD *
MOUNT FILESYSTEM(‘COLIN.ZFS1’) TYPE(ZFS) +
MOUNTPOINT(‘/colin2’) MODE(RDWR) PARM(‘AGGRGROW’) AUTOMOVE
/*

If you want to use this ZFS after an IPL you will have to mount it. If you only want to use the ZFS as a temporary ZFS you can unmount and delete it.

I created another ZFS for the unpacked Python with size MEGABYTES(550 50).

I followed the install instructions https://www.ibm.com/docs/en/python-zos/3.9?topic=configuration-installing-configuring-pax-edition using the directory /colin3.

After I had unpacked it, there was a directory usr/lpp/IBM/cyp/v3r9 with members IBM and pyz.

The path for python is /colin3/usr/lpp/IBM/cyp/v3r9/pyz/bin

You may want to consider setting up a symbolic link from /usr/lpp/pyz to the new libraries. From an authorised userid issue

ln -s /colin3/usr/lpp/IBM/cyp/v3r9/pyz /usr/lpp/pyz

Set up a profile

I set up a pythonprof file with

export LIBPATH=/usr/lpp/pyz/lib:$LIBPATH
export _BPXK_AUTOCVT=’ON’
export _CEE_RUNOPTS=’FILETAG(AUTOCVT,AUTOTAG) POSIX(ON)’
# if you are using a bash shell, you should also set these:
export _TAG_REDIR_ERR=txt
export _TAG_REDIR_IN=txt
export _TAG_REDIR_OUT=txt
export PATH=/usr/lpp/pyz/bin:$PATH

When I wanted to run a python profile, I use . ./pythonprof to do the set up.

I then checked python worked using

/usr/lpp/pyz/bin/python3 –version

Which gave me

Python 3.9.2

Install the request package and co requisites

I used the information here to install additional packages so I could use a rest interface from python. I have copied the relevant section and expanded it.

If you want to use private keys with a password you need to use package requests_pkcs12. Use Pip download requests_pkcs12 instead of download requests below.

Our z/OS service isn’t connected to the internet, so we did it like this:

On a laptop with Python and pip installed:

a. mkdir requests
b. cd requests
c. pip download requests

This pulled the “requests” package and four dependencies: The files end in .whl

1. certifi
2. chardet
3. idna
4. urllib

Binary FTP all five to a USS directory (/u/myid/pipdl)

On z/OS, in USS in the directory we uploaded to, install all of the packages using:

. /u/adcd/pythonprof
pip3 install requests --find-links ./

Note lots of error messages as pip tries to access the internet version, but then success at the end.

You can now erase the .whl files.

I ran my python programs – and they worked!