I've received some enthusiastic emails from someone who wants to
revive restricted mode. He started out with a bunch of patches to the
CPython runtime using ctypes, which he attached to an App Engine bug:
Based on his code (the file secure.py is all you need, included in
secure.tar.gz) it seems he believes the only security leaks are
__subclasses__, gi_frame and gi_code. (I have since convinced him that
if we add "restricted" guards to these attributes, he doesn't need the
functions added to sys.)
I don't recall the exploits that Samuele once posted that caused the
death of rexec.py -- does anyone recall, or have a pointer to the
--Guido van Rossum (home page: http://www.python.org/~guido/)
Alright, I will re-submit with the contents pasted. I never use double
backquotes as I think them rather ugly; that is the work of an editor
or some automated program in the chain. Plus, it also messed up my
line formatting and now I have lines with one word on them... Anyway,
the contents of PEP 3145:
Title: Asynchronous I/O For subprocess.Popen
Author: (James) Eric Pruitt, Charles R. McCreary, Josiah Carlson
Type: Standards Track
In its present form, the subprocess.Popen implementation is prone to
dead-locking and blocking of the parent Python script while waiting on data
from the child process.
A search for "python asynchronous subprocess" will turn up numerous
accounts of people wanting to execute a child process and communicate with
it from time to time reading only the data that is available instead of
blocking to wait for the program to produce data   . The current
behavior of the subprocess module is that when a user sends or receives
data via the stdin, stderr and stdout file objects, dead locks are common
and documented  . While communicate can be used to alleviate some of
the buffering issues, it will still cause the parent process to block while
attempting to read data when none is available to be read from the child
There is a documented need for asynchronous, non-blocking functionality in
subprocess.Popen    . Inclusion of the code would improve the
utility of the Python standard library that can be used on Unix based and
Windows builds of Python. Practically every I/O object in Python has a
file-like wrapper of some sort. Sockets already act as such and for
strings there is StringIO. Popen can be made to act like a file by simply
using the methods attached the the subprocess.Popen.stderr, stdout and
stdin file-like objects. But when using the read and write methods of
those options, you do not have the benefit of asynchronous I/O. In the
proposed solution the wrapper wraps the asynchronous methods to mimic a
I have been maintaining a Google Code repository that contains all of my
changes including tests and documentation  as well as blog detailing
the problems I have come across in the development process .
I have been working on implementing non-blocking asynchronous I/O in the
subprocess.Popen module as well as a wrapper class for subprocess.Popen
that makes it so that an executed process can take the place of a file by
duplicating all of the methods and attributes that file objects have.
There are two base functions that have been added to the subprocess.Popen
class: Popen.send and Popen._recv, each with two separate implementations,
one for Windows and one for Unix based systems. The Windows
implementation uses ctypes to access the functions needed to control pipes
in the kernel 32 DLL in an asynchronous manner. On Unix based systems,
the Python interface for file control serves the same purpose. The
different implementations of Popen.send and Popen._recv have identical
arguments to make code that uses these functions work across multiple
When calling the Popen._recv function, it requires the pipe name be
passed as an argument so there exists the Popen.recv function that passes
selects stdout as the pipe for Popen._recv by default. Popen.recv_err
selects stderr as the pipe by default. "Popen.recv" and "Popen.recv_err"
are much easier to read and understand than "Popen._recv('stdout' ..." and
"Popen._recv('stderr' ..." respectively.
Since the Popen._recv function does not wait on data to be produced
before returning a value, it may return empty bytes. Popen.asyncread
handles this issue by returning all data read over a given time
The ProcessIOWrapper class uses the asyncread and asyncwrite functions to
allow a process to act like a file so that there are no blocking issues
that can arise from using the stdout and stdin file objects produced from
a subprocess.Popen call.
 [ python-Feature Requests-1191964 ] asynchronous Subprocess
 Daily Life in an Ivory Basement : /feb-07/problems-with-subprocess
 How can I run an external command asynchronously from Python? - Stack
 18.1. subprocess - Subprocess management - Python v2.6.2 documentation
 18.1. subprocess - Subprocess management - Python v2.6.2 documentation
 Issue 1191964: asynchronous Subprocess - Python tracker
 Module to allow Asynchronous subprocess use on Windows and Posix
platforms - ActiveState Code
 subprocess.rst - subprocdev - Project Hosting on Google Code
 subprocdev - Project Hosting on Google Code
 Python Subprocess Dev
This P.E.P. is licensed under the Open Publication License;
On Tue, Sep 8, 2009 at 22:56, Benjamin Peterson <benjamin(a)python.org> wrote:
> 2009/9/7 Eric Pruitt <eric.pruitt(a)gmail.com>:
>> Hello all,
>> I have been working on adding asynchronous I/O to the Python
>> subprocess module as part of my Google Summer of Code project. Now
>> that I have finished documenting and pruning the code, I present PEP
>> 3145 for its inclusion into the Python core code. Any and all feedback
>> on the PEP (http://www.python.org/dev/peps/pep-3145/) is appreciated.
> Hi Eric,
> One of the reasons you're not getting many response is that you've not
> pasted the contents of the PEP in this message. That makes it really
> easy for people to comment on various sections.
> BTW, it seems like you were trying to use reST formatting with the
> text PEP layout. Double backquotes only mean something in reST.
Python code should not depend upon the ordering of items in a dict.
Unfortunately it seems that a number of tests in the standard library do
Changing PyDict_MINSIZE from 8 to either 4 or 16 causes the following
tests to fail:
test_dis test_email test_inspect test_nntplib test_packaging
test_plistlib test_pprint test_symtable test_trace
test_sys also fails, but this is a legitimate failure in sys.getsizeof()
Changing the collision resolution function from f(n) = 5n + 1 to
f(n) = n + 1 results in the same failures, except for test_packaging and
test_symtable which pass.
Finally, changing the seed in unicode_hash() from (implicit) 0 to an
arbitrary value (12345678) causes the above tests to fail plus:
test_json test_set test_ttk_textonly test_urllib test_urlparse
I think this is a real issue as the unicode_hash() function is likely to
change soon due to http://bugs.python.org/issue13703.
1. Submit one big bug report?
2. Submit a bug report for each "failing" test separately?
3. Ignore it, since the tests only fail when I start messing about?
I see PEP 418 gives time.clock_info() two boolean fields named
"is_monotonic" and "is_adjusted". I think the "is_" is unnecessary and
a bit ugly, and they could just be renamed "monotonic" and "adjusted".
A brief status update on PEP 405 (built-in virtualenv) and the open issues:
1. As mentioned in the updated version of the language summit notes,
Nick Coghlan has agreed to pronounce on the PEP.
2. Ned Deily discovered at the PyCon sprints that the current reference
implementation does not work with an OS X framework build of Python.
We're still working to discover the reason for that and determine
3. If anyone knows of a pair of packages in which both need to build
compiled extensions, and the compilation of the second depends on header
files from the first, that would be helpful to me in testing the other
open issue (installation of header files). (I thought numpy and scipy
might fit this bill, but I'm currently not able to install numpy at all
under Python 3 using pysetup, easy_install, or pip.)
On 03/15/2012 03:02 PM, Lindberg, Van wrote:
> FYI, the location of the tcl/tk libraries does not appear to be set in
> the virtualenv, even if tkinter is installed and working in the main
> Python installation. As a result, tk-based apps will not run from a
Thanks for the report! I've added this to the list of open issues in the
PEP and I'll look into it.
If you are a running a build slave or otherwise have an MSDN account
for development work, please check that your MSDN subscription is
still in effect. If the subscription expired, please let me know in
private what your subscriber ID is along with the email address you
use for the account.
Eventually we're switching to VS2010 so each slave will need to have
that version of the compiler installed.
I only had little time to spend for my open sourcing efforts, which is
why I could not get back to python-dev any time earlier...
Yesterday I forward-ported my patches to revision 76549
(13c30fe3f427), which only took 25mins or so (primarly due to the
small changes necessary to Python itself and the stability of that
parts.) Thanks to a colleague of mine (Per Larsen) I reimplemented
some of the more ugly parts of the code generator, too.
Guido's answer from the last thread was that I should duly assign the
copyright to the PSF. Unfortunatly, I don't really see any other part
than the LICENSE and README files in the Python distribution. Since my
patch basically just adds another subdirectory ("cgen") to the Python
top-level directory, I am not sure if I need to supply other
information to make my code officially PSF compatible.
Am I missing something obvious?
Issue http://bugs.python.org/issue13183 raises the point that the step
command of pdb is broken. This issue is 6 months old. A patch and test
case have been proposed. The 'Lifecycle of a Patch' at
If your patch has not received any notice from reviewers (i.e., no
comment made) after a substantial amount of time then you may email
python-dev(a)python.org asking for someone to take a look at your patch.
I am the author of pyclewn, a Vim front end to pdb and gdb, and I
would be grateful for any progress on this issue.
The following pdb session shows the problem when running the three
modules main.py, foo.py and bar.py. After the second step command, pdb
does not stop (as it should) at lines foo.py:5 and foo.py:6, nor does
it stop to print the return value of increment().
1 import foo
3 result = foo.increment(100)
4 print('result', result)
1 import bar
3 def increment(arg):
4 v = bar.value()
5 result = arg + v
6 return result
1 def value():
2 return 5
$ python -m pdb main.py
-> import foo
(Pdb) import sys; sys.version
'3.3.0a2+ (default:2c27093fd11f, Apr 30 2012, 10:51:35) \n[GCC 4.3.2]'
(Pdb) break bar.py:2
Breakpoint 1 at /path_to/bar.py:2
-> return 5
-> return 5
-> print('result', result)