stdin stdout python: how to reuse the same input file twice?

Question

I am quite new to Python and even newer to stdin stdout method. Nevertheless I need to make my script usable for UNIX commands, in order to make it possible for example to proce

Answer 1

You are trying to use an open file object as a filename:

filename = sys.stdin

# ...

input_file = open(filename, 'rU')

You cannot re-read from sys.stdin anyway; you need to read all of the file into memory, then process it twice:

if filename == '-':
    input_file = sys.stdin
else:
    input_file = open(filename, 'rU')

input_data = input_file.read()

tree = etree.fromstring(input_data)
extract(tree)

change_class(input_data)

mwhere you'll have to alter change_class to handle a string, not an open file object.