[Python-Dev] breakpoint() and $PYTHONBREAKPOINT (original) (raw)

Guido van Rossum guido at python.org
Sun Sep 10 15:16:05 EDT 2017

I think programmatic overrides should be able to decide for themselves if they want to honor PYTHONBREAKPOINT or not, since I can imagine use cases that go both ways. So it should be checked in sys.breakpointhook().

On Sun, Sep 10, 2017 at 12:06 PM, Barry Warsaw <barry at python.org> wrote:

For PEP 553, I think it’s a good idea to support the environment variable $PYTHONBREAKPOINT[*] but I’m stuck on a design question, so I’d like to get some feedback.

Should $PYTHONBREAKPOINT be consulted in breakpoint() or in sys.breakpointhook()? If we support it in breakpoint() then it means if $PYTHONBREAKPOINT is set, Python will never call sys.breakpointhook() so programmatic override of that will be ignored. If we support it in sys.breakpointhook(), then if you programmatically override that, $PYTHONBREAKPOINT will be ignored even if set. Of course, any code that overrides sys.breakpointhook() could also consult $PYTHONBREAKPOINT if they want. So how do we want it to work? It seems like explicit code should override the environment variable, which should override the default, meaning that $PYTHONBREAKPOINT should be consulted only in breakpoint(). And if you set sys.breakpointhook() with something else, then oh well, Python just ignores $PYTHONBREAKPOINT. Feedback welcome. -Barry [*] Probably not $PYTHONBREAKPOINTHOOK although if we choose to implement that in sys.breakpointhook(), it might still makes sense.

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