uncomment

#!/usr/bin/env python
"""
Removes commented lines from an input list of lines.

Commented lines are defined simply as lines that begin with "#" or ";"


Example usage:

uncomment config.ini

 - or -

cat config.ini | uncomment


Yes, I know you can do this with awk or grep or whatever, but a simple
'uncomment' is easy to remember and suits me.
"""
import sys


COMMENT_TOKENS = "#;"


def is_a_comment(line):
    line = line.strip()
    try:
        first_char = line[0]
        return first_char in COMMENT_TOKENS
    except IndexError:
        # Don't think we should be getting blank lines here, but just in case
        return False


def uncommented_lines(lines):
    for line in lines:
        if line.strip() and not is_a_comment(line):
            yield line


def process_lines(input_stream):
    for line in uncommented_lines(input_stream):
        sys.stdout.write(line)


if __name__ == "__main__":
    if not sys.stdin.isatty():
        input_stream = sys.stdin
        process_lines(sys.stdin)
        sys.exit(0)
    else:
        try:
            input_filename = sys.argv[1]
        except IndexError:
            message = "Need filename as a first argument, or use a pipe\n"
            sys.stderr.write(message)
            sys.exit(1)

        with open(input_filename, "r") as input_file:
            process_lines(input_file)
            sys.exit(0)