piping input to an external script

Mon May 11 14:04:30 EDT 2009

Hi, I have some html files that I want to validate by using an external 
script 'validate'. The html files need a doctype header attached before 
validation. The files are in utf8 encoding. My code:
---------------
import os,sys
import codecs,subprocess
HEADER = '<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">'

filename  = 'mytest.html'
fd = codecs.open(filename,'rb',encoding='utf8')
s = HEADER + fd.read()
fd.close()

p = subprocess.Popen(['validate'],
                    stdin=subprocess.PIPE,
                    stdout=subprocess.PIPE,
                    stderr=subprocess.STDOUT)
validate = p.communicate(unicode(s,encoding='utf8'))
print validate
---------------

I get lots of lines like this:
Error at line 1, character 66:\tillegal character number 0
etc etc.

But I can give the command in a terminal 'cat mytest.html | validate' and 
get reasonable output. My subprocess code must be wrong, but I could use 
some help to see what the problem is.

python2.5.1, freebsd6
thanks,
--Tim