Split strings into separate lists by regex match

Question

I have a text file that looks like this

127.0.0.1
  159.187.32.13, 3:00:15, flags: S
    Incoming interface: Ethernet51/1
    RPF route: [U] 151.177.45.0/27 [20/0] via 190.150.1.2
    Outgoing interface list:
      Vlan4054
  159.187.32.20, 2:20:11, flags: S
    Incoming interface: Ethernet51/1
    RPF route: [U] 151.177.45.59/27 [20/0] via 190.150.1.2
    Outgoing interface list:
      Vlan4054
      Vlan4056
  198.140.45.77, 2:36:15, flags: S
    Incoming interface: Ethernet51/1
    RPF route: [U] 151.177.45.88/27 [20/0] via 190.150.1.2
    Outgoing interface list:
      Vlan4054
127.0.0.2
  188.125.45.13, 3:00:15, flags: S
    Incoming interface: Ethernet51/1
    RPF route: [U] 199.150.45.0/27 [20/0] via 195.32.1.2
    Outgoing interface list:
      Vlan4054
      Vlan4056
  221.125.45.77, 2:20:11, flags: S
    Incoming interface: Ethernet51/1
    RPF route: [U] 199.150.45.10/27 [20/0] via 195.32.1.2
    Outgoing interface list:
      Vlan4054
      Vlan4056

I'm trying to create a dictionary of the data so it is parseable, currently attempting to do so via regex

import re

content = []
content_dict = {}

group_ip = re.compile("^(\d+\.\d+\.\d+\.\d+$)")
ip_subnet = re.compile("^(\d+\.\d+\.\d+\.\d+\/+\d+)")
two_space_start = re.compile("^( {2})\S")
four_space_start = re.compile("^( {4})\S")
six_space_start = re.compile("^( {6})\S")

I had planned on applying regex to each line and creating a dictionary like below

if group_ip.match(line):
    content_dict["group"] = line.strip()

elif two_space.match(line) and "RP" in line:
    line = line.split(",")

    content_dict["source"] = line[0].strip()
    content_dict["uptime"] = line[1].strip()
    content_dict["rp"] = line[2].split(" ")[-1]
    content_dict["source_flags"] = line[-1].split(":")[-1].strip()

content.append(copy.copy(content_dict))

But have realised that this won't work on scale as each group IP (127.0.0.1, 127.0.0.2) will have a variable amount of subgroups that I am overwriting. What I'm trying to get to is something along the lines of

"127.0.0.1": [
    "159.187.32.13": [
        "uptime": "3:00:15",
        "flags": "S",
        "rpf_ip": "151.177.45.0/27",
        "via": "190.150.1.2",
        "outgoing_interface": ["vlan4054"]
        ],
    "159.187.32.20": [
       "uptime": "2:20:11",
        "flags": "S",
        "rpf_ip": "151.177.45.59/27",
        "via": "190.150.1.2",
        "outgoing_interface": ["Vlan4054", "Vlan4056"]
        ]
    ]

Is it possible to get this data structure from the text through regex or some other way?

This is a JSON format. However, the key is dynamic (e.g., "127.0.0.1", "127.0.0.2"). This would be difficult to use this structured data. — yoonghm
– yoonghm, Commented Sep 18, 2018 at 8:35

blhsing · Accepted Answer · 2018-09-17 13:52:53Z

Since the input is fairly easy to tokenize, regex may be overkill. You can instead use str.startswith, str.isdigit and str.split for your purpose:

from pprint import pprint
content = {}
with open('file.txt', 'r') as f:
    for line in f:
        line = line.rstrip()
        if line[0].isdigit():
            group = line
            content[group] = {}
        elif line.startswith('  ') and line[2].isdigit():
            ip, uptime, flags = line.lstrip().split(', ')
            _, flags = flags.split()
            content[group][ip] = {'uptime': uptime, 'flags': flags, 'outgoing_interface': []}
        elif line.startswith('    RPF route:'):
            _, _, _, rpf_ip, _, _, via = line.split()
            content[group][ip]['rpf_ip'] = rpf_ip
            content[group][ip]['via'] = via
        elif line.startswith('      '):
            content[group][ip]['outgoing_interface'].append(line.lstrip())
pprint(content)

This outputs (with your sample input):

{'127.0.0.1': {'159.187.32.13': {'flags': 'S',
                                 'outgoing_interface': ['Vlan4054'],
                                 'rpf_ip': '151.177.45.0/27',
                                 'uptime': '3:00:15',
                                 'via': '190.150.1.2'},
               '159.187.32.20': {'flags': 'S',
                                 'outgoing_interface': ['Vlan4054', 'Vlan4056'],
                                 'rpf_ip': '151.177.45.59/27',
                                 'uptime': '2:20:11',
                                 'via': '190.150.1.2'},
               '198.140.45.77': {'flags': 'S',
                                 'outgoing_interface': ['Vlan4054'],
                                 'rpf_ip': '151.177.45.88/27',
                                 'uptime': '2:36:15',
                                 'via': '190.150.1.2'}},
 '127.0.0.2': {'188.125.45.13': {'flags': 'S',
                                 'outgoing_interface': ['Vlan4054', 'Vlan4056'],
                                 'rpf_ip': '199.150.45.0/27',
                                 'uptime': '3:00:15',
                                 'via': '195.32.1.2'},
               '221.125.45.77': {'flags': 'S',
                                 'outgoing_interface': ['Vlan4054', 'Vlan4056'],
                                 'rpf_ip': '199.150.45.10/27',
                                 'uptime': '2:20:11',
                                 'via': '195.32.1.2'}}}

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