On Oct 2, 2017, at 17:36, Guido van Rossum <guido@python.org> wrote:
I've seen your updates and it is now acceptable, except for *one* nit: in builtins.breakpoint() the pseudo code raises RuntimeError if sys.breakpointhook is missing or None. OTOH sys.breakpointhook() just issues a RuntimeWarning when something's wrong with the hook. Maybe builtins.breakpoint() should also just warn if it can't find the hook? Setting `sys.breakpointhook = None` might be the simplest way to programmatically disable breakpoints. Why not allow it?
Oh, actually the pseudocode doesn’t match the C implementation exactly in this regard. Currently the C implementation is more like: def breakpoint(*args, **kws): import sys missing = object() hook = getattr(sys, 'breakpointhook', missing) if hook is missing: raise RuntimeError('lost sys.breakpointhook') return hook(*args, **kws) The intent being, much like the other sys-hooks, that if PySys_GetObject("breakpointhook”) returns NULL, Something Bad Happened, so we have to set an error string and bail. (PySys_GetObject() does not set an exception.) E.g.
def foo(): ... print('yes') ... breakpoint() ... print('no') ... del sys.breakpointhook foo() yes Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in foo RuntimeError: lost sys.breakpointhook
Setting `sys.breakpoint = None` could be an interesting use case, but that’s not currently special in any way:
sys.breakpointhook = None foo() yes Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in foo TypeError: 'NoneType' object is not callable
I’m open to special-casing this if you think it’s useful. (I’ll update the pseudocode in the PEP.) Cheers, -Barry