[IPython-dev] Fwd: IPython and closing sys.stdout

[Ville M. Vainio]

I'll pick this up.

On 9/27/06, Fernando Perez <Fernando.Perez at colorado.edu> wrote:
> [ Skip, thanks for this, I'm forwarding it to ipython-dev which is subscriber
> only (too much spam).]
>
>
> Subject:IPython and closing sys.stdout
> From:skip at pobox.com
> Date:Thu, 21 Sep 2006 14:46:48 -0500
> To:ipython-dev at scipy.org
>
> John Hunter alerted me to a segfault problem in code.InteractiveConsole when
> sys.stdout is closed.  This problem is present in Python up to 2.4.3 as far
> as I can tell, but is fixed in later versions of Python (2.5, 2.4.4 when
> it's released, svn trunk).  Even with that fix, if the user calls
> sys.stdout.close() you'll get a ValueError and your console will be useless.
> I took a look at the code in Python that the InteractiveConsole class
> exercises and see that the cause is that the naive raw_input() method simply
> calls the raw_input() builtin.  That function gets the "stdin" and "stdout"
> functions from the sys module and there's no way to override that behavior.
>
> In my opinion, the best thing to do would be to subclass InteractiveConsole
> and provide a more robust raw_input() method.  Ideally, I think you'd want
> to dup() the file descriptors for sys.{stdin,stdout} and use those instead
> of calling the builtin raw_input().  Something like (untested):
>
>      class IC(code.InteractiveConsole):
>          def __init__(self):
>              code.InteractiveConsole.__init__(self)
>              self.input = os.fdopen(os.dup(sys.stdin.fileno()))
>              self.output = os.fdopen(os.dup(sys.stdout.fileno()))
>              self.error = os.fdopen(os.dup(sys.stderr.fileno()))
>
>          def raw_input(self, prompt=""):
>              if prompt:
>                  self.output.write(prompt):
>                  self.output.flush()
>              return self.input.readline()
>
>          def write(self, data):
>              self.error.write(data)
>
> Also, the runcode() method will have to be overridden to use self.output
> instead of sys.stdout.  Those couple changes should (hopefully) insulate
> IPython from such user wackiness.
>
> Skip Montanaro
> skip at pobox.com
>
>
>
>
> John Hunter alerted me to a segfault problem in code.InteractiveConsole when
> sys.stdout is closed.  This problem is present in Python up to 2.4.3 as far
> as I can tell, but is fixed in later versions of Python (2.5, 2.4.4 when
> it's released, svn trunk).  Even with that fix, if the user calls
> sys.stdout.close() you'll get a ValueError and your console will be useless.
> I took a look at the code in Python that the InteractiveConsole class
> exercises and see that the cause is that the naive raw_input() method simply
> calls the raw_input() builtin.  That function gets the "stdin" and "stdout"
> functions from the sys module and there's no way to override that behavior.
>
> In my opinion, the best thing to do would be to subclass InteractiveConsole
> and provide a more robust raw_input() method.  Ideally, I think you'd want
> to dup() the file descriptors for sys.{stdin,stdout} and use those instead
> of calling the builtin raw_input().  Something like (untested):
>
>     class IC(code.InteractiveConsole):
>         def __init__(self):
>             code.InteractiveConsole.__init__(self)
>             self.input = os.fdopen(os.dup(sys.stdin.fileno()))
>             self.output = os.fdopen(os.dup(sys.stdout.fileno()))
>             self.error = os.fdopen(os.dup(sys.stderr.fileno()))
>
>         def raw_input(self, prompt=""):
>             if prompt:
>                 self.output.write(prompt):
>                 self.output.flush()
>             return self.input.readline()
>
>         def write(self, data):
>             self.error.write(data)
>
> Also, the runcode() method will have to be overridden to use self.output
> instead of sys.stdout.  Those couple changes should (hopefully) insulate
> IPython from such user wackiness.
>
> Skip Montanaro
> skip at pobox.com
>
>
>
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>
>
>


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Ville M. Vainio - vivainio.googlepages.com
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