2013/3/20 anatoly techtonik <[email protected]>
> On Wed, Mar 20, 2013 at 5:28 PM, Amaury Forgeot d'Arc
> <[email protected]>wrote:
>
>> 2013/3/20 anatoly techtonik <[email protected]>
>>
>>> Hi,
>>>
>>> I've created a module to dump function trace during execution of Python
>>> script. You can see session example in attachment. The format is of PHP
>>> Xdebug tool [2] just because I had some scripts from the past to analyze it.
>>>
>>> The module uses sys.settrace() to analyse frames in 'call' events with
>>> callback(frame, event, arg).
>>>
>>> Recently I've got an anonymous report that some frame misses filename
>>> information when run under IDE:
>>>
>>> https://bitbucket.org/techtonik/xtrace/issue/2/use-of-xtrace-module-within-ide-causes
>>>
>>> There is unlikely to be any more feedback from the user to make me
>>> understand and reproduce the behavior, nor there is a sufficient
>>> documentation in sys.trace description [1]. So I am on my own. But I can
>>> not read C code the CPython is written in, so I ask here.
>>>
>>> What are possible execution contexts for Python?
>>> How each execution context affects data structure that is passed to
>>> trace function (frame and arg)?
>>>
>>
>> It's simpler than that: when running from an interactive session, f_back
>> is empty...
>>
>> >>> def trace(frame, event, arg):
>> ... funcname = frame.f_code.co_name
>> ... if funcname == '<module>':
>> ... print frame.f_back.f_code.co_filename
>> ...
>> >>> import sys
>> >>> sys.settrace(trace)
>> >>> 1
>> Traceback (most recent call last):
>> File "<stdin>", line 1, in <module>
>> File "<stdin>", line 4, in trace
>> AttributeError: 'NoneType' object has no attribute 'f_code'
>>
>
> Thanks a lot. =)
>
> User said he was using module from the IDE and at first I thought it
> wasn't possible to use module without previous stack frame (f_back), but I
> was wrong:
>
> > py -2 -s -S
> Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)]
> on win32
> >>> import xtrace
> >>> xtrace.start()
> TRACE START [2013-03-20 18:49:27]
> >>> z = 0
> -> decode() C:\Python27\lib\encodings\cp437.py:14
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "xtrace.py", line 66, in function_trace_xdebug
> filename = self._strip_cwd(frame.f_back.f_code.co_filename)
> AttributeError: 'NoneType' object has no attribute 'f_code'
>
>
> On the way I've discovered that my Python is hacked. Without -s -S key it
> executes modules from local temp directory.
> ...
> -> ensure_unicode()
> c:\users\user\appdata\local\temp\easy_install-k8gvbp\pyreadline-1.7.1-py2.7-win32.egg.tmp\pyre
> dline\unicode_helper.py:20
> ...
>
>
> So there are absolutely no differences in running code in these execution
> contexts?
> - code runs from a file
> - code runs from a interactive console
>
Of course there is a difference; the code below works run from a file, but
not when pasted into the interactive console:
def trace(frame, event, arg):
funcname = frame.f_code.co_name
print frame.f_code, repr(frame.f_code.co_code), event, arg
if funcname == '<module>':
print " module", repr(frame.f_back.f_code.co_code)
import sys
sys.settrace(trace)
exec '1 + 1'
>
> I realize that I don't know how to set trace function for external file,
> so that when the file is executed, the first frame won't have the previous
> stack frame. I do it like so:
> start()
> execfile(script)
> stop()
>
I'ts indeed difficult to detach the "script" from the frame running the
execfile statement.
You could handle this case specially in your trace function, though.
--
Amaury Forgeot d'Arc
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