構成内の新しい変数を置き換えて追加するためにスクリプトを変更するにはどうすればよいですか？

私は次のようにすることができます：

testing = True

if testing: ##################################################################

    infile = '''
key0=0
key1=1
 key1 = 1
key2=2 # comment1
#key3=3
  #key4=4
#key5=5 # comment
  #key6=6 # comment
key7=7

key8 = 8
    '''

    infilelines = infile.split('\n')


    class of():
        def write(self, s):
            print s
        def close(self):
            pass
    outfile = of()

    replacements = {
        'key1' :'11repl',
        'key2' :'22repl',
        'key3' :'33repl',
        'key4' :'44repl',
        'key5' :'55repl',
        'key6' :'66repl',
        }


else: #########################################################################

    # as proposed by csny, only open file quickly
    # (file is closed after with statement)
    with open('sysctl.conf') as infile:
        infilelines = infile.readlines()

    outfile = open('sysctl.conf.new', 'w')

    replacements = {'Net.ipv4.icmp_echo_ignore_all' :'1',
        'Net.ipv4.icmp_echo_ignore_broadcasts' :'1',
        'Net.ipv4.ip_forward' : '0',
        'Net.ipv4.tcp_syncookies':'1',
        'Net.ipv4.conf.all.rp_filter': '1',
        'Net.ipv4.conf.all.Log.martiansd':'1',
        'Net.ipv4.conf.all.Secure_redirects' : '1',
        'Net.ipv4.conf.all.Send_redirects' : '0',
        'Net.ipv4.conf.all.Accept_Source_Route':  '0',
        'Net.ipv4.conf.all.Accept_redirects':'0',
        'Net.ipv4.tcp_max_syn_backlog': '4096',
        }



for line in infilelines:

    # if # at the beginning (neglecting whitespaces): its only a line comment
    # write it directly to outfile and continue with next line
    if len(line.strip())==0 or line.strip()[0] == '#':
        outfile.write(line.strip())
        continue

    # try if this is a properly formated line like: key=val
    try:
        key, val = line.split('=')
        key = key.strip()
        val = val.strip()

    # something stange happend: It was not a proper key=val line
    # dont modify anything, just write the line to the new file
    except ValueError:
        # or comment out outfile.write to delete the strange line
        # from the output config file
        outfile.write(line)
        continue

    # maybe you want to allow line end comments like: key=val # comment?
    # lets try if the value actually contains a comment
    try:
        val, comment = val.split('#')
        comment = '# ' + comment.strip()
        val = val.strip()

    # there is no comment at the end of the line
    # (the val.split() returns only one value and thus the unpacking fails with:
    # ValueError: need more values to unpack)
    except ValueError:
        comment = ''


    # replace the val if the according key in the `replacements` dict
    # with the value stored in the key
    # otherwise don't change anything
    if key in replacements.keys():
        val = replacements[key]

    # put together the new line for the output file
    line = '%s=%s   %s' % (key, val, comment)
    outfile.write(line)

outfile.close()

コードのコメントをご覧ください。これは構成ラインを分離し、キーが辞書に存在する場合は値を変更し、最後に出力ファイルに印刷するためにラインを再組み立てします。行末にコメントを追加することもできます。