[IMPORTANT] Changes to python operation for Chromium developers

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Alex Ovsienko

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Aug 4, 2026, 11:03:40 AM (15 hours ago) Aug 4
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Hello Chromium developers,


This announcement might affect how your developer's machine operates, so please read it carefully.


We are announcing that we are creating python3 and python3.bat files in depot_tools that, if your Chromium developer setup is correct, will take over the system python3 references and point to CIPD provided Python currently at 3.11.8 version. This is done as a part of the effort to improve Python hermeticity and reproducibility, together with being able to control the Python version for all of our clients.


Now, if this change is something you would like to avoid, we provide an escape hatch: please set the environment variable DEPOT_TOOLS_PYTHON_BYPASS to anything but 0 and calling python3 will result in calling the system Python again.


If you have any questions or issues, please report them in cr/542430166.


--

 Alex Ovsienko

Dirk Pranke

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Aug 4, 2026, 1:18:22 PM (13 hours ago) Aug 4
to ovsi...@google.com, chromi...@chromium.org
Hi Alex,

In the past, we had concerns around (a) overriding what the system might expect the default version of python to be (particularly on Mac) and (b) making it too difficult for a user to control the version of python they themselves wanted; to address the hermeticity and versioning concerns we provided `depot_tools/python-bin` and/or recommended people use `vpython`. 

Your note sounds like a change (or even reversal) of that policy. Is that correct? I'm curious what, if anything, changed that led to this decision.

-- Dirk

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