[Python-Dev] [Python-checkins] cpython: Close #19762: Fix name of _get_traces() and _get_object_traceback() function

[Victor Stinner]

2013/11/25 Jim Jewett <jimjjewett at gmail.com>:
> Why are these functions (get_traces and get_object_traceback) private?

_get_object_traceback() is wrapped to get a nice Python object:
http://hg.python.org/cpython/file/6ec6facb69ca/Lib/tracemalloc.py#l208

_get_traces() is private, it is used internally by take_snapshot():
http://hg.python.org/cpython/file/6ec6facb69ca/Lib/tracemalloc.py#l455

So it's possible to modify the low-level (private) structure used in
the C module without touching the high-level (public) Python API.

> (1)  Is the whole module provisional?  At one point, I had thought so, but I
> don't see that in the PEP or implementation.  (I'm not sure that it should
> be provisional, but I want to be sure that the decision is intentional.)

I don't know.

> (2)  This implementation does lock in certain choices about the nature of
> traces.  (What data to include for analysis vs excluding to save memory;
> which events are tracked separately and which combined into a single total;
> organizing the data that is saved in a hash by certain keys; etc)
>
> While I would prefer more flexibility, the existing code provides a
> reasonable default, and I can't forsee changing traces so much that these
> functions *can't* be reasonably supported unless the rest of the module API
> changes too.

Sorry, I don't see which kind of information is "excluded" to save memory.

Maybe you read an old version of the PEP?

About "events": tracemalloc doesn't store functions calls as event,
there is no timestamp. I didn't try to implement that, and I doesn't
want to. If you develop it (maybe on top of tracemalloc, I mean by
modify _tracemalloc.c), I would be interested to see your code and
test it :-)

> (3)  get_object_traceback is the killer app that justifies the specific
> data-collection choices Victor made; if it isn't public, the implementation
> starts to look overbuilt.

It is public, see the doc and the doc:
http://docs.python.org/dev/library/tracemalloc.html#tracemalloc.get_object_traceback
http://www.python.org/dev/peps/pep-0454/

> (4) get_traces is about the only way to get at even the all the data that
> *is* stored, prior to additional summarization.  If it isn't public, those
> default summarization options become even more locked in..

Snapshot.traces contains exactly the same data than _get_traces().

In a previous version of the PEP/code, statistics were computed while
traces were collected. It's not more the case. Now the API only
collect raw data, and then you have call to Snapshot.statistics() or
Snapshot.compare_to().

Victor