using pipe with python
Question: 
    import re
    import subprocess
    
    sub = subprocess.Popen(['/home/karthik/Downloads/stanford-parser-2011-06-   08/lexparser.csh'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr = subprocess.PIPE)
    
    sub.stdin.write("i am a fan of ac milan which is the best club in the world")
    
    relns = []
    
    while(True):
        rel = sub.stdout.readline()
            m = re.search("Sentence skipped", rel)
    
        if m != None:
                print 'stop'
                sys.exit(0)
    
            if rel == '\n':
                    break
            relns.append(rel) 
    
    print relns
    
    sub.terminate()
    

So i want to the stanford parser and using the lexparser.csh to parse this
line of text . But when i run this piece of code i am a getting the output of
the default of text. The actual text given in is not being parsed. So am i
using pipes the right way ?And i've seen in a lot of examples - a '-' is used
along with the command . Why is that being used ? Cos when i use that the
script just stalls at sub.stdout.readline()


Answer: You may need to call `flush()` on `sub.stdin` after writing.

