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I'm running a python binary target with bazel run xxx and in the target I'm doing print(sys.version). This outputs Python version 3.6.8 (default, Jan 14 2019, 11:02:34)

When I type the python command directly, I get Python 3.7.3 (default, Apr 3 2019, 19:16:38)

Why/how did bazel choose a different python version?

Mark
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1 Answers1

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Bazel will choose different python versions based on the configuration of the build. If nothing is overriden, bazel will use its default python version. This can be overridden by passing --python_version=<some_version> when running a bazel command.

https://docs.bazel.build/versions/master/be/python.html#py_binary.python_version https://github.com/bazelbuild/rules_python/blob/120590e2f2b66e5590bf4dc8ebef9c5338984775/python/BUILD#L43

Dave Hughes
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    "If nothing is overriden, bazel will use its default python version" how does that work? where is that default defined?, the link you provided says "default is `_INTERNAL_SENTINEL`" why is that? Also, it seems the valid values for `python_version` are `PY2` and `PY3`, which Python 3 version? why `3.6.8` in the case of the original question and not `3.7.3`? – Juan Enrique Muñoz Zolotoochin Sep 22 '21 at 19:04