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line-by-line output from a subprocess

Jp Calderone exarkun at divmod.com
Mon May 23 16:58:00 EDT 2005 
On 23 May 2005 13:22:04 -0700, Simon Percivall <percivall at gmail.com> wrote:
>Okay, so the reason what you're trying to do doesn't work is that the
>readahead buffer used by the file iterator is 8192 bytes, which clearly
>might be too much. It also might be because the output from the
>application you're running is buffered, so you might have to do
>something about that as well.
>
>Anyway, if the output from the child application is unbuffered, writing
>a generator like this would work:
>
>def iterread(fobj):
>    stdout = fobj.stdout.read(1) # or what you like
>    data = ""
>    while stdout:
>        data += stdout
>        while "\n" in data:
>            line, data = data.split("\n", 1)
>            yield line
>        stdout = fobj.stdout.read(1)
>    if data:
>        yield data,
>

Or, doing the same thing, but with less code:

    def iterread(fobj):
        return iter(fobj.readline, '')

Haven't tried this on subprocess's pipes, but I assume they behave much the same way other file objects do (at least in this regard).

Jp
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