[New-bugs-announce] [issue14803] Add -C option to run code at Python startup

[Nick Coghlan]

New submission from Nick Coghlan <ncoghlan at gmail.com>:

Reading http://nedbatchelder.com/code/coverage/subprocess.html, it occurred to me that there are various tracing and profiling operations that could be cleanly handled with significantly less work on the part of the tracing/profiling tool authors if the interpreter supported a "-C" operation that was like the existing "-c" option, but *didn't* terminate the options list.

The interpreter would invoke such commands after the interpreter is fully initialised, but before it begins the processing to find and execute __main__.

Then, to use subprocess coverage with coverage.py as an example, you could just run a command like:

"python -C 'import coverage; coverage.process_startup()' worker.py"

Other things you could usefully do in such an invocation is reconfigure sys.std(in|out|err) to match the settings used on the invoking side (e.g. to ensure Unicode data is tunnelled correctly), configure the logging module with a custom configuration, configure the warnings module programmatically, enable a memory profiler, etc.

Providing a function that could be called from -C and then uses an atexit() handler to do any necessary post-processing may be significantly simpler than trying to use runpy.run_(path|module) to achieve a similar effect.

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messages: 160597
nosy: ncoghlan
priority: normal
severity: normal
status: open
title: Add -C option to run code at Python startup

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue14803>
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