Line-by-line processing when stdin is not a tty

[RG]

In article <rNOSPAMon-3CC595.13205911082010 at news.albasani.net>,
 RG <rNOSPAMon at flownet.com> wrote:

> In article <i3uu74$uga$1 at speranza.aioe.org>,
>  Tim Harig <usernet at ilthio.net> wrote:
> 
> > On 2010-08-11, RG <rNOSPAMon at flownet.com> wrote:
> > > In article <i3uo7t$6mk$1 at speranza.aioe.org>,
> > >  Tim Harig <usernet at ilthio.net> wrote:
> > >
> > >> On 2010-08-11, RG <rNOSPAMon at flownet.com> wrote:
> > >> > I'm writing a system in a different language but want to use a Python 
> > >> > library.  I know of lots of ways to do this (embed a Python 
> > >> > interpreter, 
> > >> > fire up a python server) but by far the easiest to implement is to 
> > >> > have 
> > >> > the main program spawn a Python interpreter and interact with it 
> > >> > through 
> > >> > its stdin/stdout.
> > >> 
> > >> Or, open python using a socket.
> > >
> > > You mean a TCP/IP socket?  Or a unix domain socket?  The former has 
> > > security issues, and the latter seems like a lot of work.  Or is there 
> > > an easy way to do it that I don't know about?
> > 
> > I was referring to unix domain sockets or more specifically stream
> > pipes. I guess it depends what language you are using and what libraries
> > you have access to.  Under C, working with stream pipes is no more trivial
> > then using pipe().  You can simply create the socket descriptors using
> > socketpair().  Keep one of the descriptors for your process and pass the
> > other to the python child process as both stdin and stdout.
> 
> Ah.  That is in fact exactly what I am doing, and that is how I first 
> encountered this problem.
> 
> rg

And now I have encountered another problem:

-> print sys.stdin.encoding
<- None

But when I run from a terminal:

[ron at mickey:~]$ python
Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.stdout.encoding
'UTF-8'


I thought the value of sys.stdin.encoding was hard-coded into the Python 
executable at compile time, but that's obviously wrong.  So how does 
Python get the value of sys.stdin.encoding?

rg