def readlines(arg):
    """Read lines from a file into a list.

    Removes whitespace and lines that start with '#'
    """
    fin = open(arg)
    lines_in = fin.readlines()
    fin.close()
    lines_out = []
    for line in lines_in:
        line = line.strip()
        if not line or line[0] == '#':
            continue
        lines_out.append(line)
    return lines_out