So, I am a novice with python. I'm trying to teach myself python just to expand my skills.

I gave myself a simple challenge and I need some guidance here on how to get it done.

The goal is to read in a dhcpd leases file, read through the lease records, and end up with a list of dictionary items for each lease.

The input file will look like this:

lease {
  starts 2 2012/03/13 10:24:01;
  ends 2 2012/03/20 10:24:01;
  cltt 2 2012/03/13 10:24:01;
  binding state active;
  next binding state free;
  hardware ethernet 90:4c:e5:18:5c:24;
  uid "\001\220L\345\030\\$";
lease {
  starts 4 2012/03/15 00:44:53;
  ends 4 2012/03/22 00:44:53;
  cltt 4 2012/03/15 00:44:53;
  binding state active;
  next binding state free;
  hardware ethernet 00:24:d7:2b:43:d0;
  uid "\001\000$\327+C\320";
  set ddns-fwd-name = "pc.domain.local.";
  set ddns-txt = "3100bdf5ca9dabd07e5a8ef0ffe4755fc5";
  set ddns-rev-name = "";
  client-hostname "pc";
lease {
  starts 4 2012/03/15 03:34:56;
  ends 4 2012/03/22 03:34:56;
  cltt 4 2012/03/15 03:34:56;
  binding state active;
  next binding state free;
  hardware ethernet 00:0e:35:97:e4:30;
  set ddns-rev-name = "";
  set ddns-txt = "00fc80f10784541b93c67f45b46993d112";
  set ddns-fwd-name = "t42.domain.local.";
  client-hostname "t42";

Each lease item has its set of attributes.
Now if each lease was on its own line, I'm sure I could do this using the examples from the tutorials I've been through with a line split. But I can't get my head around how to read in the block of info and then extract the items to a dictionary.

This was simple attempt:

file_to_parse = '/home/kane/djangodev/dhcpmon/sampledhcplease.txt'
file_to_write = '/home/kane/djangodev/dhcpmon/dhcpleaseoutput'
leaselist = []

filein = open(file_to_parse)
fileout = open(file_to_write,'w') 

for line in filein.readlines():
    current_line = line.strip()
    splitline = current_line.split()

    #Ignore blank lines... this is tested first before an index error on the next test
    if len(splitline)== 0:
        #do nothing

    #Ignore comments and black lines in the file
    if splitline[0].startswith ('#'):
        #do nothing

    if splitline[0].startswith ('lease'):
        newlinetoadd = []

Here's where I get stuck. I was going to build a list with the lease IP as 1st item, but then I realized I couldn't continue to the next line without messing up the for loop.

I'm sure I'm taking the wrong approach here. Perhaps I need to readin the whole file as a long string the split the string on the '}' character? then take each split item and split it again on the ';' character?

I'm not looking for an answer... just a push in the right direction.

Edited by Dani: Formatting

5 Years
Discussion Span
Last Post by pyTony

Nice way to get formatted input is to use generator function with for:

def get_leases(fn):
    with open(fn) as lease_file:
        block = ''
        for line in lease_file:
            if block and line.startswith('lease'):
                yield block
                block = ''
            block += line
        if block:
            yield block

for no, lease in enumerate(get_leases('lease.txt'), 1):
    print('lease {}:\n{}'.format(no, lease))
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