[Python-Dev] API design question: how to extend sys.settrace()?
hrvoje.niksic at avl.com
Wed Sep 27 10:44:14 EDT 2017
On 09/27/2017 02:56 PM, Victor Stinner wrote:
> In bpo-29400, it was proposed to add the ability to trace not only
> function calls but also instructions at the bytecode level. I like the
> idea, but I don't see how to extend sys.settrace() to add a new
> "trace_instructions: bool" optional (keyword-only?) parameter without
> breaking the backward compatibility. Should we add a new function
One possibility would be for settrace to query the capability on the
part of the provided callable.
if getattr(tracefn, '__settrace_trace_instructions__', False):
... we need to trace instructions ...
In general, the "trace function" can be upgraded to the concept of a
"trace object" with (optional) methods under than __call__. This is
extensible, easy to document, and fully supports the original
"old=sys.gettrace(); ...; sys.settrace(old)" idiom.
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