[Python-3000] sys.exc_info()

[Antoine Pitrou]

Adam Olsen <rhamph <at> gmail.com> writes:
> 
> The bytecode generation for "raise" could be changed literally be the
> same as "except Foo as e: raise e".  Reuse our existing stack, not add
> another one.

As someone else pointed, there is a difference between the two constructs: the
latter appends a line to the traceback while the former doesn't. I suppose in
some contexts it can be useful (especially if the exception is re-raised several
times because of a complex architecture, e.g. a framework).

> The commented out raise should use the outer except block (and thus be
> lexically based), but sys.exc_info() doesn't have to be.

But would you object to sys.exc_info() being lexically based as well?
I say that because the bare "raise" statement and sys.exc_info() use the same
attributes internally, so they will have the same semantics unless we decide
it's better to do otherwise.

> > Also, "yield" cannot blindingly clear the exception state, because the frame
> > calling the generator may except the exception state to be non-None.
> > Consequently, we might have to keep the f_exc_* members solely for the
> > generator case.
> 
> Why?  Why should the frame calling the generator be inspecting the
> exception state of the generator?  What's the use case?

You misunderstood me. The f_exc_* fields will be used internally to swap between
the inner generator's exception state and the calling frame's own exception
state. They will have no useful meaning for outside code so I suggest they are
not accessible from Python code anymore.

Regards

Antoine.