REXX and Python can, in many scenarios, solve similar problems, they belong to different worlds within z/OS and serve distinct needs.
REXX is a mainframe-native language, deeply integrated into z/OS. It fits naturally into the TSO/E and ISPF universe, allowing for the execution of system commands, automation of ISPF dashboards, direct manipulation of datasets, and generation or submission of JCLs with extreme simplicity. Being part of the traditional ecosystem, REXX is usually available in virtually any z/OS environment, without the need to install additional runtimes or external libraries. This characteristic makes it a safe and stable choice for operational automations and day-to-day administrative tasks.
Python, on the other hand, is not native to z/OS, but today it is well established in the environment through Unix System Services (USS) and initiatives such as z/OS Open Tools and IBM SDKs. Its main strength lies in its vast ecosystem of libraries and the ease of working with modern integrations. Tasks such as consuming REST APIs, parsing JSON, automating pipelines, analyzing logs, and integrating with external tools are much more natural in Python than in REXX.
In short: it depends on the goal.
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Matheus Porsch
Systems Administration - Kyndryl
Brazil
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Original Message:
Sent: Tue January 06, 2026 06:10 AM
From: Steve Spence
Subject: Is Python now the main language to use on the Mainframe?
I am just opening this question as I have been asked, should Python be the primary programming language to use today as it does have a lot of versatility over some of the more traditional ones?
Yes, I know it is going to depend on what you are doing but for example would you put Python before REXX as they can both do what you require.
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Steve Spence
Expert Systems Engineer, Applications
Ensono Ltd
London
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