Mensanator wrote: > I don't know why you're using stdin if you're reading from a file.
>From Francesco's initial post in his previous thread I inferred that he had a script like f = open("xxx.pdb") for line in f: # process line print line and was calling it python script.py >outfile My hope was that import sys for line in sys.stdin: # process line sys.stdout.write(line) invoked as python script.py <xxx.pdb >outfile would be an improvement as it avoids hardcoding the filename, but instead chaos ensued... Francesco: Mensanator's script looks like you can take it "as is". If you want to use Python to do other interesting things I highly recommend that you work your way through a tutorial of your choice. This will make subsequent trial-and-error much more fun. Following Roy's suggestion I also had a brief look at Biopython's PDB parser which has the advantage that it "understands" the file format. Unfortunately it is probably too complex for you to use at this point of your career as a pythonista ;) By the way, are you trying to modify the chain ID? Biopython locates that at position 21, so take this as a reminder that indices in Python start at 0, i. e. line[21] gives you the 22nd character in the line. Peter -- http://mail.python.org/mailman/listinfo/python-list