Piping data into script under Win32

[runes]

I trying to figure out a way to make a python script accept data output
from another process under Windows XP, but I fail miserably. I have a
vague memory having read this is not possible with Python under
Windows...

But googling for a clue I came across this from /Learning Python/ (Lutz
& Ascher) [1]


<Learning Python>

import sys
data = sys.stdin.readl ines()
print "Counted", len(data), "lines."

On Unix, you could test it by doing something like:


% cat countlines.py | python countlines.py
Counted 3 lines.

On Windows or DOS, you'd do:


C:\> type countlines.py | python countlines.py
Counted 3 lines.

</Learning Python>


So: Is it possible to pipe data under DOS/Win9x but not NT/2k/XP or is
it a bug in /Learning Python/ ?


I've tried about all kinds of sane and insane approaches involving
sys.stdin, but they all results in IOError: [Errno 9] Bad file
descriptor.


[1] <http://www.oreilly.com/catalog/lpython/chapter/ch09.html>

[Jaime Wyant]

Re: Piping data into script under Win32

I can't think of any reason that wouldn't work. You've entered the
code in exactly like you have it below?

Could you paste the traceback from your console?

jw

On 15 Apr 2005 19:11:44 -0700, runes <rune.strand@gm ail.com> wrote:[color=blue]
> I trying to figure out a way to make a python script accept data output
> from another process under Windows XP, but I fail miserably. I have a
> vague memory having read this is not possible with Python under
> Windows...
>
> But googling for a clue I came across this from /Learning Python/ (Lutz
> & Ascher) [1]
>
> <Learning Python>
>
> import sys
> data = sys.stdin.readl ines()
> print "Counted", len(data), "lines."
>
> On Unix, you could test it by doing something like:
>
> % cat countlines.py | python countlines.py
> Counted 3 lines.
>
> On Windows or DOS, you'd do:
>
> C:\> type countlines.py | python countlines.py
> Counted 3 lines.
>
> </Learning Python>
>
> So: Is it possible to pipe data under DOS/Win9x but not NT/2k/XP or is
> it a bug in /Learning Python/ ?
>
> I've tried about all kinds of sane and insane approaches involving
> sys.stdin, but they all results in IOError: [Errno 9] Bad file
> descriptor.
>
> [1] <http://www.oreilly.com/catalog/lpython/chapter/ch09.html>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>[/color]

[R. C. James Harlow]

Re: Piping data into script under Win32

On Saturday 16 April 2005 03:11, runes wrote:[color=blue]
> I trying to figure out a way to make a python script accept data output
> from another process under Windows XP, but I fail miserably. I have a
> vague memory having read this is not possible with Python under
> Windows...
>
> C:\> type countlines.py | python countlines.py
> Counted 3 lines.[/color]

Are you definitely doing this and not:

C:\> type countlines.py | countlines.py

That will give you the error you're seeing. The example you posted works for
me.

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[runes]

Re: Piping data into script under Win32

You being so sure about what you were saying, was what I needed.
Thanks!

Under Windows, I'm used to rely on the PATHEXT env. variable, so I
typically don't write "python scriptname.py args", but just "scriptname
args".

So:
type countlines.py | python countlines.py = Success
type countlines.py | countlines.py = Failure

Why doesn't the latter work?

Traceback:
F:\groks>type countlines.py | countlines.py
The process tried to write to a nonexistent pipe.
Traceback (most recent call last):
File "C:\groks\count lines.py", line 2, in ?
data = sys.stdin.readl ines()
IOError: [Errno 9] Bad file descriptor

[R. C. James Harlow]

Re: Piping data into script under Win32

On Saturday 16 April 2005 03:43, runes wrote:
[color=blue]
> type countlines.py | python countlines.py = Success
> type countlines.py | countlines.py = Failure
>
> Why doesn't the latter work?[/color]

Don't quote me on this, but I think it's because invoking countlines.py
involves running some sort of wrapper that discards its stdin and stdout.

If anyone has a more authorative answer, I'd like to know, because this caught
me out too.

james.

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[runes]

Re: Piping data into script under Win32

Thanks James! I'll post the explanation if I find it ;-)

Rune