Custom Popen.communicate Method Gives Wrong Output

Let's start by considering this code: proc_stdin.py import sys if __name__ == '__main__': for i, line in enumerate(sys.stdin): sys.stdout.write(line) test.py import s

Solution 1:

If you strip newlines from every line and then add them back between the lines, what happens to the last newline (if any)? (There’s no final, empty line after a final newline because your iter discards it.) This is why Python’s readline (or line iteration) function includes the newlines: they’re necessary to represent the end of the file accurately.