Terry J. Reedy added the comment:
https://docs.python.org/3/library/functions.html#bool refers to
https://docs.python.org/3/library/stdtypes.html#truth
The latter says that values are true ("All other values are considered true")
unless one of certain conditions holds. For user-defined classes, the
condition is that the class defines a __bool__() or __len__() method and that
the first of those methods returns the bool False or integer zero.
I easily interpret this as meaning that bool(x) (should) *always* return True
or False. In particular, for user classes, any exception in user-coded
__bool__ or __len__ (should be) included in "does not return integer zero or
bool value False". This would mean that 'True' would truly be the default
return for Bool().
There is currently an unstated exception for raised Exceptions. This issue
proposes an exception to the exception for OverflowErrors (once negative
lengths consistently raise ValueErrors and never OverflowErrors). While this
sensible in itself, I am completely happy with the added complication. I would
like to either reconsider the exception for Exceptions or make it explicit.
Patch has new text and What's New entry. Added logic in object.c looks correct.
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nosy: +terry.reedy
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<http://bugs.python.org/issue29840>
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